CADDO LAKE WATERSHED PROTECTION PLAN Technical Memo (Task 1.2.3) Prepared for: Northeast Texas Municipal Water District 4180 FM 250 P.O. Box 955 Hughes Springs, TX 75656 By: Espey Consultants, Inc. EC Project No. 8041 3809 South 2nd St., Suite B-300 Austin, Texas 78704 November 17, 2008 T (512) 326-5659 F (512) 326-5723 www.espeyconsultants.com
Technical Memo (Task 1.2.3) TABLE OF CONTENTS 1.0 INTRODUCTION...5 2.0 APPROACH FOR DATA ANALYSIS...9 2.1 DISCUSSION OF WATER QUALITY PARAMETERS...9 2.2 SCREENING CRITERIA...9 2.3 DATA INVENTORY AND SUMMARY STATISTICS...10 2.4 TREND ANALYSIS...11 2.5 HANDLING NON-DETECTS AND OTHER DATA DISCREPANCIES...11 2.6 RANKING AND PRIORITIZATION...15 3.0 LITTLE CYPRESS CREEK BASIN DATA AND TREND ANALYSIS...16 3.1 BACTERIA...17 3.2 TOTAL PHOSPHORUS (TP)...24 3.3 AMMONIA...29 3.4 NITRITE-NITRATE (NOX)...34 3.5 OTHER PARAMETERS OF INTEREST...39 3.6 TREND ANALYSIS - PH...49 3.7 TREND ANALYSIS - DO...49 4.0 BIG CYPRESS CREEK BASIN DATA AND TREND ANALYSIS...54 4.1 BACTERIA...55 4.2 TOTAL PHOSPHORUS...66 4.3 AMMONIA...75 4.4 NITRITE-NITRATE (NOX)...84 4.5 OTHER PARAMETERS OF INTEREST...92 4.6 TREND ANALYSIS - PH...107 4.7 TREND ANALYSIS - DO...114 5.0 CADDO LAKE DATA AND TREND ANALYSIS...122 5.1 TOTAL PHOSPHORUS...127 5.2 AMMONIA...130 5.3 NITRITE-NITRATE (NOX)...132 5.4 OTHER PARAMETERS OF INTEREST...135 5.5 TREND ANALYSIS - PH...141 5.6 TREND ANALYSIS - DO...146 6.0 PRIORITIZING POLLUTANT SOURCE PARAMETERS BY LOCATION...153 6.1 LANDUSE CHARACTERIZATION...153 6.2 FLOW VS. CONCENTRATION RELATIONSHIPS...156 6.3 PRECIPITATION VS. CONCENTRATION RELATIONSHIPS...171 6.4 POINT SOURCES...172 6.5 NON-POINT SOURCES...174 6.6 RANKING OF POLLUTANT SOURCE PARAMETERS BY LOCATION...175 7.0 MODELING RECOMMENDATIONS...179 7.1 WATERSHED MODELING...179 7.2 STREAM MODELING...180 7.3 LAKE MODELING...180 8.0 CONCLUSIONS...182 8.1 LITTLE CYPRESS CREEK ANALYSIS SUMMARY...183 8.2 BIG CYPRESS CREEK ANALYSIS SUMMARY...184 8.3 CADDO LAKE ANALYSIS SUMMARY...184 9.0 REFERENCES...185 i
Technical Memo (Task 1.2.3) Appendix A... A Appendix B... B Appendix C... C FIGURES Figure 1. Cypress Creek Basin Segmentation by EC...7 Figure 2. Caddo Lake Segmentation by EC...8 Figure 3. EC Segments 1 and 2 SWQM Stations...16 Figure 4. EC Segment 3 and 4 SWQM Stations...17 Figure 5. EC Segment 1 of the Little Cypress Creek Bacteria Concentration Observations...19 Figure 6. EC Segment 2 Lilly Creek Bacteria Concentration Observations...20 Figure 7. EC Segment 3 of the Little Cypress Creek Bacteria Concentration Observations...22 Figure 8. EC Segment 4 of the Little Cypress Creek Bacteria Concentration Observations...24 Figure 9. EC Segment 1 Little Cypress Creek Total Phosphorus Observations...25 Figure 10. EC Segment 2 Lilly Creek in the Little Cypress Creek Total Phosphorus Observations...26 Figure 11. EC Segment 3 Little Cypress Creek Total Phosphorus Observations....27 Figure 12. EC Segment 4 Little Cypress Creek Total Phosphorus Observations....28 Figure 13. EC Segment 1 Little Cypress Creek Ammonia Observations....30 Figure 14. EC Segment 2 Little Cypress Creek Ammonia Observations....31 Figure 15. EC Segment 3 Little Cypress Creek Ammonia Observations....32 Figure 16. EC Segment 4 Little Cypress Creek Ammonia Observations....33 Figure 17. EC Segment 1 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations....35 Figure 18. EC Segment 2 Lilly Creek in the Little Cypress Creek Basin Total Nitrite-Nitrate (NOx) Concentration Observations...36 Figure 19. EC Segment 3 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations...37 Figure 20. EC Segment 4 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations...38 Figure 21. Orthophosphate Concentrations for EC Segment 1...40 Figure 22. Orthophosphate Concentrations for EC Segment 2...41 Figure 23. Orthophosphate Concentrations for EC Segment 3...42 Figure 24. Orthophosphate Concentrations for EC Segment 4...43 Figure 25. Chlorophyll-a Concentrations for EC Segment 1...45 Figure 26. Chlorophyll-a Concentrations for EC Segment 2...46 Figure 27. Chlorophyll-a Concentrations for EC Segment 3...47 Figure 28. Chlorophyll-a Concentrations for EC Segment 4...48 Figure 29. ph Trends for Little Cypress Creek...50 Figure 30. DO Trends for Little Cypress Creek Basin...51 Figure 31. SWQM Station Locations for EC Segments 5, 7, 8, 11, and 12...54 Figure 32. SWQM Station Locations for EC Segments 4, 5, 6, 9, 10, 11, 12 and 13...55 Figure 33. Bacteria Concentrations for EC Segment 5...57 Figure 34. Bacteria Concentrations for EC Segment 6...58 Figure 35. Bacteria Concentrations for EC Segment 9...58 Figure 36. Bacteria Concentrations for EC Segment 10...60 Figure 37. Bacteria Concentrations for EC Segment 7...62 Figure 38. Bacteria Concentrations for EC Segment 8...63 Figure 39. Bacteria Concentrations for EC Segment 12...63 Figure 40. Bacteria Concentrations for EC Segment 11...64 Figure 41. Bacteria Concentrations for EC Segment 13...66 Figure 42. Total Phosphorus Concentrations in EC Segment 5...67 Figure 43. Total Phosphorus Concentrations in EC Segment 6...68 Figure 44. Total Phosphorus Concentrations in EC Segment 9...68 Figure 45. Total Phosphorus Concentrations in EC Segment 10...69 Figure 46. Total Phosphorus Concentrations in EC Segment 7...71 Figure 47. Total Phosphorus Concentrations in EC Segment 8...72 Figure 48. Total Phosphorus Concentrations in EC Segment 12...73 Figure 49. Total Phosphorus Concentrations in EC Segment 11...74 ii
Technical Memo (Task 1.2.3) Figure 50. Total Phosphorus Concentrations in EC Segment 13...75 Figure 51. EC Segment 5 Black Cypress Creek Ammonia Observations....76 Figure 52. EC Segment 6 Big Cypress Creek Ammonia Observations...77 Figure 53. EC Segment 9 Haggerty Creek Ammonia Observations...77 Figure 54. EC Segment 10 Big Cypress Bayou Ammonia Observations....78 Figure 55. EC Segment 7 Jim Bayou Ammonia Observations...80 Figure 56. EC Segment 8 Frazier Creek Ammonia Observations....80 Figure 57. EC Segment 12 James Bayou Ammonia Observations...81 Figure 58. EC Segment 11 Kitchen Creek Ammonia Observations...82 Figure 59. EC Segment 13 Harrison Bayou Ammonia Observations...83 Figure 60. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 5....85 Figure 61. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 6....85 Figure 62. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 9....86 Figure 63. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 10....87 Figure 64. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 7....88 Figure 65. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 8....89 Figure 66. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 12....90 Figure 67. Total Nitrite-Nitrate Nitrogen (NOx) Concentartions in EC Segment 11...91 Figure 68. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 13....92 Figure 69. Orthophosphate Concentrations in EC Segment 5....93 Figure 70. Orthophosphate Concentrations in EC Segment 6....94 Figure 71. Orthophosphate Concentrations in EC Segment 10....94 Figure 72. Chlorophyll-a Concentrations in EC Segment 5....95 Figure 73. Chlorophyll-a Concentrations in EC Segment 6....96 Figure 74. Chlorophyll-a Concentrations in EC Segment 9....96 Figure 75. Chlorophyll-a Concentrations in EC Segment 10....97 Figure 76. Chlorophyll-a Concentrations in EC Segment 7....99 Figure 77. Chlorophyll-a Concentrations in EC Segment 8....100 Figure 78. Chlorophyll-a Concentrations in EC Segment 12....100 Figure 79. Orthophosphate Concentrations in EC Segment 7....101 Figure 80. Orthophosphate Concentrations in EC Segment 8....102 Figure 81. Orthophosphate Concentrations in EC Segment 12....103 Figure 82. Orthophosphate Concentrations in EC Segment 11....104 Figure 83. Orthophosphate Concentrations in EC Segment 13....104 Figure 84. Chlorophyll-a Concentrations in EC Segment 11....105 Figure 85. Chlorophyll-a Concentrations in EC Segment 13....106 Figure 86. ph Trends in the Big Cypress Bayou...108 Figure 87. ph Values in EC Segment 7...110 Figure 88. ph Values in EC Segment 8...111 Figure 89. ph Values in EC Segment 12...111 Figure 90. ph Values in EC Segment 11...112 Figure 91. ph Values in EC Segment 13...113 Figure 92. DO Trends in the Big Cypress Bayou...116 Figure 93. DO Trends in James Bayou (EC Segments...117 Figure 94. DO Concentrations in EC Segment 11...118 Figure 95. DO Concentrations in EC Segment 13...119 Figure 96. Fecal Coliform Concentrations in Caddo Lake....124 Figure 97. E. coli Concentrations in Caddo Lake...126 Figure 98. Total Phosphorus Concentrations in Caddo Lake...129 Figure 99. Caddo Lake Ammonia Observations...132 Figure 100. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in Caddo Lake...135 Figure 101. Chlorophyll-a Concentrations in Caddo Lake...138 Figure 102. Orthophosphate Concentrations in Caddo Lake...140 Figure 103. ph Values in Caddo Lake...146 Figure 104. DO Concentrations in Caddo Lake...151 Figure 105. Land Use Characterization for the Cypress Creek Watershed....155 iii
Technical Memo (Task 1.2.3) Figure 106. Flow vs. Concentration Relationships for EC Segment 4....160 Figure 107. Flow vs. Concentration Relationship for EC Segment 5...164 Figure 108. Flow vs. Concentration Relationships for EC Segment 6...168 Figure 109. Flow vs. Concentration Relationships for EC Segment 10...171 Figure 110. Point Sources...173 TABLES Table 1. Cypress Creek Basin Segmentation and Assignment of SWQM Stations...6 Table 2. Applicable TCEQ Water Quality Standards and Assessment Screening Levels for the Cypress Creek Basin...10 Table 3. Comparison of Methods to Address Non-Detection Value Effect on Data Analysis for Total Phosphorus.13 Table 4. Summary Statistics by Segment for the Little Cypress Creek...52 Table 5. Big Cypress Creek Basin Summary Statistics by Segment...120 Table 6. Summary Statistics for Caddo Lake by Sub-Area...152 Table 7. Land Use Comparison and Conversion for the Cypress Creek Basin...154 Table 8. Ranking of Pollutant Source Parameters by the Mean Concentration...175 Table 9. Prioritization of Parameters for Concern at Watershed Segments based on Available Data...176 Table 10. Additional Recommendations for Future Monitoring Efforts in the Cypress Creek Basin and Caddo Lake...177 Table 11. Summary of Findings Compared to 303 (d) List and 2008 Water Quality Inventory...183 iv
1.0 INTRODUCTION Caddo Lake Watershed Protection Plan Espey Consultants, Inc. (EC) was retained by the Northeast Texas Municipal Water District in April 2008 to participate in the development of the Watershed Protection Plan (WPP) for Caddo Lake. The WPP project encompasses not only Caddo Lake but also the contributing Cypress Creek Basin. This memorandum is the Task 1.2.3 deliverable of EC s scope which also included: participating in the stakeholder process, identifying (with the help of the stakeholder groups) what water quality parameters are important, obtaining and reviewing relevant data, identifying data gaps and/or needs, recommending additional data collection or monitoring, and recommending a modeling approach for the next phase of the WPP. EC s data analysis may also be useful in the Texas Commission on Environmental Quality s (TCEQ) Triennial Review of the Texas Water Quality Standards; consideration is being given to division of the Caddo Lake water quality segment into two segments, "Caddo Lake" and "Caddo Swamp". TCEQ will continue to evaluate appropriate water quality standards for Caddo as part of the long-term effort to address the 303(d) listing in Category 5c (TCEQ, 2008). The task of ranking the potential source locations of pollutants was achieved by taking a thorough inventory of available water quality data. The portion of the basin upstream of Lake O the Pines was not evaluated since a TMDL has already been completed with an Implementation Plan underway. EC divided the Cypress Creek Basin into 13 major stream reaches (Figure 1) and Caddo Lake into nine lake segments (Figure 2). Several of the EC segments correspond with the segments identified in the 303(d) list. The stream segments were broken into new reaches at the confluence of another stream reach or major tributary. Surface Water Quality Monitoring (SWQM) stations were assigned to these stream reaches accordingly (Table 1). The Caddo Lake segments group SWQM sites based on the contributing stream segment and location along the lake (Figure 2). Existing water quality data primarily consist of SWQM data provided by the Texas Commission for Environmental Quality (TCEQ) and supplemental bacteria data from East Texas Baptist University (Dr. Roy Darville). Dr. Darville has collected bacterial data on several segments. These data were included in the analysis to supplement the SWQM data for these segments. The parameters evaluated in this study included dissolved oxygen (DO), ph, ammonia (NH 3 ), total nitrite-nitrate nitrogen (NOx), total phosphorus (TP), orthophosphate (OP), chlorophyll-a, and bacteria (fecal coliform and E. coli). Mercury contamination was previously studied in the Cypress River Basin and has been determined to be a significant contaminant (TCEQ, 2004b). Currently, Texas is conducting a statewide effort to study the best approach for detecting and managing mercury levels in waterbodies. Therefore, mercury will not be a primary focus of this WPP. However, the WPP stakeholder group will need to be involved in reviewing the statewide effort as it pertains to Caddo Lake. It should also be noted that two Continuous Water Quality Monitoring (CWQM) stations, or sometimes referred to as Continuous Ambient Monitoring Stations (CAMS), are located within Caddo Lake. Station C707, located mid-lake, and station C708, located in the upper mid-lake, are maintained by the Caddo Lake Institute and were established October 1, 2003 and are both currently active. Both of these stations monitor surface water temperature, specific conductance, DO, and ph hourly. In addition, station C707 monitors meteorological parameters including wind speed and direction, precipitation, and outdoor temperature. Station C707 also in the past measured bottom water temperature, specific conductance, DO, and ph. This data was not included in this analysis due to the stations close proximity to other stations where plentiful monthly DO and ph data already exist. The hourly ambient water and meteorological data will be a useful dataset for lake modeling in Phase II of this project. 5
ECSegment Caddo Lake Watershed Protection Plan Table 1. Cypress Creek Basin Segmentation and Assignment of SWQM Stations Description 1 Little Cypress Creek upstream of Lilly Creek 14975 16017 16453 17478 2 Lilly Creek 15834 17953 17954 Stations 3 Little Cypress Creek downstream of Lilly Creek 10279 10280 10333 10334 10335 14996 16533 16861 18203 18590 4 Little Cypress Bayou 10331 10332 15773 16532 5 Black Cypress Bayou 6 Big Cypress Bayou (Creek) upstream of Black Cypress Bayou, downstream of Lake O'Pines 7 Jim Bayou 10243 10244 10245 10246 10247 10248 14474 16258 16705 16936 16935 16934 13630 15135 15511 10254 10257 10320 10321 10322 10323 10324 10325 10326 10327 10328 14976 18200 10256 10255 8 Frazier Creek 10258 10259 17619 18201 9 Haggerty Creek 14997 16253 10-Main Big Cypress Bayou downstream of Black Cypress Bayou 10-HW Big Cypress Bayou at headwaters of Caddo Lake 10294 15023 11 Kitchen Creek 14998 12 James Bayou 10260 10319 10295 14471 15021 15022 15248 16254 13-Main Harrison Bayou 16365 15506 15507 15508 15509 13-HW Harrison Bayou at headwaters of Caddo Lake 10285 10286 14 Caddo Lake 14-NW Clinton Lake (fed by Kitchen Creek) 14236 14-SW1 near headwaters of Big Cypress Bayou 10292 10293 15249 14-SW2 downstream of 14-SW1, cove of Caddo Lake 10288 10289 10291 15275 14-SW3 downstream of SW1 and SW2, at confluence of Big Cypress Bayou and Harrison Bayou 10287 14946 17867 14-NC downstream of SW3 along northern shore 10282 10283 14-SC downstream of SW3 along southern shore 10287 14946 17867 14-NE1 14-NE2 near headwaters of Jeems Bayou downstream of NE1 along shore station shown on SWQM map, not in database station shown on SWQM map, not in database 14-E near outlet of Caddo Lake station shown on SWQM map, not in database 6
Figure 1. Cypress Creek Basin Segmentation by EC. 7
12 11 NW NE1 NE2 10HW 10 SW2 SW1 NC E SW3 13HW SC 13 Figure 2. Caddo Lake Segmentation by EC. 8
2.0 APPROACH FOR DATA ANALYSIS 2.1 DISCUSSION OF WATER QUALITY PARAMETERS Caddo Lake Watershed Protection Plan DO and ph are field parameters that are indicators of overall waterbody health. Conventional parameters (nutrients and other associated nutrient indicators) are often collected in conjunction with field parameters in order to determine causes of decreased quality. Nutrients such as nitrogen and phosphorus enhance plant growth (Sawyer et al., 1994) which in excess can limit the use attainment of waterbodies. These nutrients can be from natural sources (decomposition of plant materials), attached to deposited sediment, or present in the water after a runoff flush event carrying nutrients form the land surface into the water bodies and then transported downstream. Chlorophyll-a is a plant pigment whose concentration is an indicator of the amount of algal biomass and growth in the water column. Chlorophyll-a is discussed in the nutrients section of this report because it is related to the amount of nutrients present in the waterbody. Elevated levels of bacteria can also cause limited recreational use and can also lead to depressed DO levels. In the past, fecal coliform was measured as the indicator organism for bacteria in streams. In recent years, the indicator was changed to E. coli, which is a bacterial organism that lives in the intestines of warm blooded animals and excreted in animal waste. 2.2 SCREENING CRITERIA The TCEQ provides numeric criteria for DO, ph, and bacteria (fecal coliform and E. coli) in Section 30 Texas Administrative Code (TAC) Chapter 307 Texas Surface Water Quality Standards. The numeric criteria set in this document is based on aquatic life and human use attainment. For nutrients and related parameters, the TCEQ provides recommended screening criteria in the Guidance for Assessing and Reporting Surface Water Quality Data (TCEQ, 2008) based on the observed concentration levels in all the waterbodies in the state. The screening level is set at the 85 th percentile and can be used as a gage of water quality in comparison to other waterbodies in the state. Table 2 is a detailed list of the applicable TCEQ Water Quality Standards and Assessment Screening Levels for the parameters address in this report for the Cypress Creek Basin. The stream criteria were applied for EC Segments 1 through 13 and the reservoir standards were applied to the Caddo Lake subareas and the stations at the headwaters of Caddo Lake (EC Segment 10-HW and EC Segment 13-HW). According to the Guidance for Assessing and Reporting Surface Water Quality Data in Texas (TCEQ, 2008), a minimum of 10 samples over a seven year period of record are required for assessment of use attainment. In addition, stations in an assessment area may be aggregated to meet the minimum sample requirement. An assessment of concern can be made for sample sizes 4 and < 10 but such an assessment is not as significant as when the minimum 10 sample requirement is met. When the mean (or geometric mean for bacteria) exceeds the standard/criteria limit ( Table 2 ) or when more than 20% of the samples exceed the criteria/standard (grab sample limit for bacteria) under specific monitoring schemes the watercourse is considered a concern or impaired. In this assessment the terms concern and impaired will be avoided since these terms refer to a specific classification assigned by the regulatory agency (TCEQ). Instead, EC will use the terms impeded, elevated, depressed, and relevant issue to describe locations and parameters where this assessment has addressed and identified as pertinent for focusing mitigation efforts. This determination is made when the historical mean exceeds the standard/criteria limit or when more than 25% of the samples exceed the criteria/standard. A relevant issue will also be indicated when a particular parameter has an adverse trend over the period of record. 9
Table 2. Applicable TCEQ Water Quality Standards and Assessment Screening Levels for the Cypress Creek Basin Recreational Waters 1 : 126 geometric mean indicator bacteria (E. coli) per 100mL (or Fecal coliform 200 per 100mL) <394 grab sample indicator bacteria (E. coli) per 100mL (or Fecal coliform 400 per 100mL) High Aquatic Life Use in Cypress Creek Basin 1 : 5 mg/l mean DO except in Black Cypress Bayou and James Bayou 4 mg/l mean DO Additional Criteria 1 : 6.0 8.5 ph except in Little Cypress Creek 5.5 8.5 ph Streams 2 : Total Phosphorus (TP) 0.69 mg/l Orthophosphate 0.37 mg/l Total Nitrate + Nitrite (NOx) 3 2.76 mg/l Chlorophyll-a 14.1 µg/l Ammonia 0.33 mg/l Reservoirs 2 : Total Phosphorus (TP) 0.20 mg/l Orthophosphate 0.05 mg/l Total Nitrate+Nitrite (NOx) 3 0.32 mg/l Chlorophyll-a 26.7 µg/l Ammonia 0.11 mg/l Footnotes: 1 30 TAC CHAPTER 307 - TEXAS SURFACE WATER QUALITY STANDARDS 2 2008 Draft Guidance for Assessing and Reporting Surface Water Quality in Texas 3 Guidance for Assessing Texas Surface and Finished Drinking Water Quality Data, 2004 2.3 DATA INVENTORY AND SUMMARY STATISTICS Data from TCEQ s Surface Water Quality Monitoring database were sorted by assigning water quality stations to segments (Table 1). The database was then filtered for the water quality parameters of interest for this study by segment for the entire period of record. Additional bacteria data was supplemented (where available) from Dr. Roy Darville at East Texas Baptist University. Dr. Darville conducts routine studies of Caddo Lake separate from the Clean Rivers Program (CRP) conducted by TCEQ and does not necessarily follow the same quality assurance standards as the SWQM dataset but is still considered reliable and comparable data. Statistical parameters (mean, median, maximum, minimum, 25 th percentile, and number of samples) were calculated by segment for each pollutant parameter of interest. The geometric mean, often referred to as the geomean, was calculated for bacteria (Equation 1) including all of the data in the dataset instead of the arithmetic average computed for the other parameters. Error! Objects cannot be created from editing field codes. Equation 1 where: n = number of samples x i = the i th sample 10
The geomean was used because the observations are only a snapshot of time and bacteria concentrations are often very volatile and can change drastically based on the time of measurement. The geomean dampens the influence of variability to help address this concern. Finally, time series plots of measured water parameter concentrations were created for each segment. Plots were also created for each water quality station to determine the source location of pollutants through a stream segment and identify areas of the segment that should be monitored more extensively for various parameters (examples found in Appendix A). The percent exceedances for each parameter at each station as well as a per segment basis were calculated, see Appendix B, to identify pollutant concerns and their location. The source location is useful for identifying pollutant contributors, whether point or nonpoint sources. Also located in Appendix B is the summarized period of record for each parameter at each station, grouped by segment. 2.4 TREND ANALYSIS Data for each segment and parameter were plotted to determine trends and compare historic data against the screening criteria levels. For DO and ph sufficient data was available to plot with the linear regression line with 95% confidence intervals of the mean response. These plots were only presented in this report when a trend was evident based on the slope of the regression; otherwise the data was plotted with the bounds of the standard criteria. The trends for the remaining parameters were evaluated by simply plotting the values in time series to determine if the concentrations in the segment have tended to increase or decrease with time. 2.5 HANDLING NON-DETECTS AND OTHER DATA DISCREPANCIES Errors can be found in measured data, thus it is important to consider the effects of these errors prior to data analysis and determination of trends. One source of error is in data reported at the detection limit, referred to as non-detects (measurements at or below the laboratory detection limit based on confidence in results). This is especially important to consider when the detection limit is close to the screening criteria and may make the difference between a segment being classified as a concern or not. Another potential source of error is from data collected at different time periods (with various laboratory methods) and by different collecting entities (again with varying laboratory methods). In order to account for these errors and determine if these are actually playing a significant role in data analysis in the Cypress Creek Basin, EC addressed these issues in various ways. For the non-detects (NDs), EC first compared the statistical parameters for total phosphorus (TP) by handling the ND data with various approaches upon consultation with Dr. George Ward (University of Texas at Austin). The first approach kept the ND value at the reported value, the second approach divided the reported ND value in half (this assumes the actual value is somewhere between zero and the reported limit), the third approach was to set the ND values equal to zero, and the fourth approach removed the ND data completely from the analysis by assigning a null value. The most significant difference was found when the data were completely removed from the analyses because the low values were essentially screened out of the analyses creating an artificially high average concentration (Table 3). As expected, setting the values to zero created the lowest mean concentrations compared to the other approaches. Overall, the differences between setting equal to zero, halving, or setting equal to the detection limit were not significant when comparing the mean. Of course, the magnitude of the effect depended on the percentage of data reported at the detection limit. Despite only minimal differences in most cases, EC decided, the fairest approach for the scope of this assessment was to halve the data reported at the detection limit for data analyses in all segments and for all parameters and to leave the values at the detection limit for plotting the time series. 11
TCEQ staff identified risks associated with utilizing the SWQMIS database. Datasets taken at the same location and time may yield different results based on the data source. It has been determined that different lab methods for the same parameter may yield slightly different results. Laboratories will also use different reporting limits. It was suggested that EC perform an evaluation of the data based on the data source to determine if mixing data from multiple sources had an effect on the overall result. EC plotted the data at each station within the basin for each parameter addressed in this report and differentiated the data with various symbols based on the different data sources and different colors to discriminate the non-detection values. Preliminary investigation of these plots indicates that in most cases no significant differences in magnitude were present between the laboratories utilized in the Cypress Creek Basin. Examples of the plots utilized in this analysis are provided in Appendix A. However, in some cases, the data were tested by one entity for some period of record then by another facility for the next period of record without overlap. Since the extent of the this kind of error is difficult to assess and is beyond the scope of this study, it is simply noted that variation in lab results from testing entities are a possible source of error and should be considered when making generalities about historic trends. 12
Table 3. Comparison of Methods to Address Non-Detection Value Effect on Data Analysis for Total Phosphorus Max Segment Zeroed NDs Value Adjusted NDs Difference Removed NDs 1 mean 0.0972 0.1156 0.1064 0.0183 0.1458 median 0.0700 0.0750 0.0700 0.0050 0.0950 max 0.6600 0.6600 0.6600 0.6600 min 0.0000 0.0100 0.0050 0.0160 25th Percentile 0.0000 0.0600 0.0300 0.0700 n 60 (20) 60 60 (20) 40 (20) 2 mean 0.2069 0.2132 0.2100 0.0063 0.2570 median 0.1700 0.1700 0.1700 0.0000 0.2520 max 0.8300 0.8300 0.8300 0.8300 min 0.0000 0.0100 0.0050 0.0100 25th Percentile 0.0300 0.0400 0.0400 0.1340 n 41 (8) 41 41 (8) 33 (8) 3 mean 0.2792 0.2811 0.2801 0.0019 0.2972 median 0.1900 0.1900 0.1900 0.0000 0.1900 max 7.0600 7.0600 7.0600 7.0600 min 0.0000 0.0100 0.0050 0.0500 25th Percentile 0.1135 0.1135 0.1135 0.1200 n 99 (6) 99 99 (6) 93 (6) 4 mean 0.1236 0.1251 0.1244 0.0015 0.1280 median 0.0900 0.0910 0.0900 0.0010 0.1000 max 1.3400 1.3400 1.3400 1.3400 min 0.0000 0.0100 0.0050 0.0200 25th Percentile 0.0615 0.0667 0.0615 0.0700 n 236 (8) 236 236 (8) 228 (8) 5 mean 0.0972 0.1018 0.0995 0.0046 0.1076 median 0.0900 0.0900 0.0900 0.0000 0.0980 max 0.3890 0.3890 0.3890 0.3890 min 0.0000 0.0100 0.0050 0.0200 25th Percentile 0.0555 0.0600 0.0555 0.0678 n 239 (23) 239 239 (23) 216 (23) 6 mean 0.0414 0.0574 0.0494 0.0160 0.0601 median 0.0200 0.0500 0.0300 0.0300 0.0400 max 0.6100 0.6100 0.6100 0.6100 min 0.0000 0.0100 0.0050 0.0100 25th Percentile 0.0000 0.0270 0.0250 0.0200 n 106 (33) 106 106 (33) 73 (33) 7 mean 0.1454 0.1482 0.1468 0.0028 0.1591 median 0.0900 0.0900 0.0900 0.0000 0.0900 max 0.8500 0.8500 0.8500 0.8500 min 0.0000 0.0100 0.0050 0.0200 25th Percentile 0.0500 0.0560 0.0500 0.0600 n 93 (8) 93 93 (8) 85 (8) 13
8 mean 0.0760 0.0793 0.0776 0.0033 0.0901 median 0.0420 0.0500 0.0500 0.0080 0.0500 max 0.9800 0.9800 0.9800 0.9800 min 0.0000 0.0090 0.0050 0.0090 25th Percentile 0.0225 0.0250 0.0250 0.0300 n 51 (8) 51 51 (8) 43 (8) 9 mean 0.2699 0.3074 0.2886 0.0375 0.3598 median 0.2750 0.2750 0.2750 0.0000 0.3630 max 0.6890 0.6890 0.6890 0.6890 min 0.0000 0.0500 0.0500 0.0500 25th Percentile 0.0375 0.1750 0.0875 0.2545 n 8 (2) 8 8 (2) 6 (2) 10-M mean 0.0920 0.0955 0.0937 0.0035 0.0983 median 0.0700 0.0700 0.0700 0.0000 0.0700 max 0.8500 0.8500 0.8500 0.8500 min 0.0000 0.0100 0.0050 0.0100 25th Percentile 0.0400 0.0440 0.0400 0.0490 n 188 (12) 188 188 (12) 176 (12) 10-HW mean 0.0781 0.0781 0.0781 0.0000 0.0781 median 0.0500 0.0500 0.0500 0.0000 0.0500 max 0.3400 0.3400 0.3400 0.3400 min 0.0300 0.0300 0.0300 0.0300 25th Percentile 0.0500 0.0500 0.0500 0.0500 n 16 (0) 16 16 (0) 16 (0) 11 mean 0.1708 0.2136 0.1922 0.0429 0.2391 median 0.1400 0.1480 0.1400 0.0080 0.1480 max 0.4820 0.4820 0.4820 0.4820 min 0.0000 0.0854 0.0500 0.0854 25th Percentile 0.0427 0.1200 0.0927 0.1400 n 7 (2) 7 7 (2) 5 (2) 12 mean 0.0932 0.0950 0.0941 0.0018 0.0961 median 0.0515 0.0560 0.0515 0.0045 0.0520 max 1.2090 1.2090 1.2090 1.2090 min 0.0000 0.0100 0.0100 0.0100 25th Percentile 0.0335 0.0390 0.0335 0.0380 n 66 (2) 66 66 (2) 64 (2) 13-M mean 0.1725 0.1906 0.1815 0.0181 0.2070 median 0.1400 0.1430 0.1400 0.0030 0.1540 max 0.8710 0.8710 0.8710 0.8710 min 0.0000 0.0350 0.0175 0.0670 25th Percentile 0.0998 0.1218 0.1068 0.1350 n 24 (4) 24 24 (4) 20 (4) 13-HW mean 0.2167 0.2333 0.2250 0.0167 0.2600 median 0.0400 0.0750 0.0500 0.0350 0.0500 max 0.8200 0.8200 0.8200 0.8200 min 0.0000 0.0200 0.0200 0.0200 25th Percentile 0.0225 0.0350 0.0350 0.0300 n 6 (1) 6 6 (1) 5 (1) 14 mean 0.0865 0.0986 0.0925 0.0121 0.1079 median 0.0500 0.0600 0.0500 0.0100 0.0600 max 1.3500 1.3500 1.3500 1.3500 min 0.0000 0.0100 0.0050 0.0150 25th Percentile 0.0240 0.0400 0.0300 0.0400 n 181 (36) 181 181 (36) 145 (36) Another source of data discrepancy is the occurrence of outliers. Outliers can skew data significantly, depending upon the number of samples and the magnitude of the outlier. In this report an outlier is defined as a measured value that is not in congruence (at least 1 order of magnitude above the median) with the majority of values in the data record. When an outlier was detected, the observed value was 14
removed from the summary statistic calculations but was plotted in the charts and included in the period of record summary. 2.6 RANKING AND PRIORITIZATION As part of the scope of work for this project, EC developed a ranking system for the segments and parameters of interest. The ranking procedure utilized the mean values of each parameter in each segment. The parameters were ranked to identify the areas in the Cypress River Basin that need to be focused on in terms of source identification, best management practices and/or modeling activities. In addition, other statistical parameters (such as the median and 25 th percentile), and the recent data trends were also used to prioritize the pollutant parameters in each segment that need to be addressed through further monitoring and implementing management plans. The detailed ranking and prioritization discussion is found in Section 6 of this report. 15
3.0 LITTLE CYPRESS CREEK BASIN DATA AND TREND ANALYSIS Little Cypress Creek watershed consists of four EC Segments (Figure 1). The segments include: 1 (Little Cypress Creek above Lilly Creek), 2 (Lilly Creek), 3 (Little Cypress Creek below Lilly Creek), and 4 (Little Cypress Creek further downstream, above the confluence of Big Cypress Bayou). Segment 1 is shown as the lower red area in Figure 3 and contains SWQM stations 14975 and 16017. Segment 2 is the larger red area in Figure 3 and contains SWQM stations 17953, 17954, 15833, 15835, and 15834. Segment 3 is shown in Figure 4 and contains SWQM stations 10335, 10334, 10333, and 16861. 2 17953 17954 15833 15835 1 15834 14975 16453 17478 16017 3 Figure 3. EC Segments 1 and 2 SWQM Stations 16
2 14995 5 1 10280 14996 10334 16533 10279 10333 18203 3 16861 15773 6 10331 10332 4 10 16532 15001 10250 9 3.1 BACTERIA Figure 4. EC Segment 3 and 4 SWQM Stations Bacteria data were plotted for each segment in the Little Cypress Creek basin (Figure 5, Figure 6, Figure 7, and Figure 8). EC Segments 2 and 3 are impeded for bacteria (E. coli only) based on the geometric mean (Table 4). In addition, EC Segment 1 is impeded at station 14975 due to the percent of grab samples exceeding the standard (Appendix B Segment 1). For EC Segment 1 the tributary stations have much lower E. coli concentrations than the main stretch of the segment and were separated out for the numerical analysis (Table 4). All of the exceedances above the grab sample criteria for E. coli in EC Segment 2 were observed at station 17953 (Appendix B Segment 2). In addition, samples at station 17953 exceeded the E. coli geomean criteria 90% of the time. Samples further downstream at Station 17954 (Figure 3) exceed the screening level criteria for the geometric mean for about 78% of occurrences but no samples at this station were higher than the grab sample criteria. Station 15834, the furthest downstream station in EC Segment 2 (Figure 3), was only monitored for fecal coliform between Oct 1999 and Jul 2001 and did not indicate any relevant issues for bacteria but should be monitored (for E. coli) due the rising levels of bacteria upstream. EC Segment 3 has a lower geometric mean concentration for E. coli than EC Segment 2 (Table 4). This segment was monitored for fecal coliform the most extensively at station 10334 (Figure 4) between 1992 and 2000 and did not indicate relevant issues based on the grab sample screening. E. coli was monitored in this segment at stations 10335, 16861, and 18590 (Figure 4). Station 16861 is the only station with enough reported data for analyses (> 10 samples). Station 16861 had 6 out of 22 samples exceed the grab sample criteria indicating a bacteria relative impediment in EC Segment 3 at that location (Appendix B Segment 3). The reported data for EC Segment 4 do not currently indicate any bacteria impediments. However, station 10332 does exceed the grab sample limit 15% of the time during the period of record, has a geometric mean of 120, a median of 130, and a rising trend in the past two years. This is an indication that bacteria from further upstream in the watershed 17
could be contributing downstream and has the potential for contributing bacteria to EC Segment 10 and thusly Caddo Lake if management practices are not implemented. 10000 Segment 1 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 14975 Detections Approximate Location 16017 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 1 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14975 Detections Approximate Location 16017 Detections Grab Sample Criteria Geomean Criteria 18
10000 Segment 1 Tributary E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 16453 Detections 17478 Detections Approximate Location 17478 Non-Detects Grab Sample Criteria Geomean Criteria 10000 Segment 1 Tributary Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16453 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 5. EC Segment 1 of the Little Cypress Creek Bacteria Concentration Observations 19
10000 Segment 2 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 17953 Detections Approximate Location 17954 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 2 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15834 Detections 15834 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Figure 6. EC Segment 2 Lilly Creek Bacteria Concentration Observations. 20
10000 Segment 3 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10335 Detections Approximate Location 16861 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 3 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1980 1985 1990 1995 2000 2005 2010 10333 Detections 10334 Detections Approximate Location 10335 Detections 16861 Detections Grab Sample Criteria Geomean Criteria 21
Segment 3 Tributary E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 18590 Detections Approximate Location Grab Sample Criteria Geomean Criteria 10000 Segment 3 Tributary Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14996 Detections 16533 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 7. EC Segment 3 of the Little Cypress Creek Bacteria Concentration Observations 22
10000 Segment 4 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10332 Detections Approximate Location 15773 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 4 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10332 Detections 10332 Non-Detects Approximate Location 15773 Detections Grab Sample Criteria Geomean Criteria 23
Segment 4 Tributary Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16532 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 8. EC Segment 4 of the Little Cypress Creek Bacteria Concentration Observations 3.2 TOTAL PHOSPHORUS (TP) The historic TP concentrations were plotted against the screening criteria (Figure 9, Figure 10, Figure 11, and Figure 12). None of the Little Cypress Creek Basin segments indicate a relevant issue based on the stream criteria for total phosphorus. The highest average concentration is found in EC Segment 3 (0.28 mg/l) followed by EC Segments 2, 4, and 1 respectively (Table 4). For EC Segment 1 the tributary stations have much lower average TP concentrations than the main stretch of the segment and were separated out for the numerical analysis (Table 4) and thus reordering the ranking of average TP from highest to lowest to EC Segments 3, 2, 1, and 4, respectively. Although at all the segments the mean concentration TP are well below the screening criteria TP should be addressed in EC Segment 2. This segment has a significant increase in TP from 2000 to 2006. Additional data should be collected to determine if a trend exists or if watershed best management practices have lowered that trend. In addition, the levels of TP found in all of these segments could indicate excess nutrients which encourage algal growth. 24
Figure 9. EC Segment 1 Little Cypress Creek Total Phosphorus Observations 25
Figure 10. EC Segment 2 Lilly Creek in the Little Cypress Creek Total Phosphorus Observations 26
Figure 11. EC Segment 3 Little Cypress Creek Total Phosphorus Observations. 27
Figure 12. EC Segment 4 Little Cypress Creek Total Phosphorus Observations. 28
3.3 AMMONIA Caddo Lake Watershed Protection Plan The historic ammonia concentrations were plotted against the screening criteria (Figure 13, Figure 14, Figure 15, and Figure 16). None of the Little Cypress Creek Basin segments indicate a relevant issue based on the stream criteria for ammonia. The highest average concentration is found in EC Segment 2 (0.19 mg/l) followed by EC Segments 3, 1, and 4 respectively (Table 4). 29
Figure 13. EC Segment 1 Little Cypress Creek Ammonia Observations. 30
Figure 14. EC Segment 2 Little Cypress Creek Ammonia Observations. 31
Figure 15. EC Segment 3 Little Cypress Creek Ammonia Observations. 32
Figure 16. EC Segment 4 Little Cypress Creek Ammonia Observations. 33
3.4 NITRITE-NITRATE (NOx) Caddo Lake Watershed Protection Plan The Little Cypress Creek Basin historic data for total nitrite-nitrate was plotted against the screening criteria for each segment (Figure 17, Figure 18, Figure 19, and Figure 20). All of the Little Cypress Creek Basin segments had mean concentrations below the total Nitrate + Nitrite (NOx) concentration screening criteria (<2.76 mg/l). Comparatively, Segment 3 was the highest (0.45 mg/l) followed by Segments 2 (0.33 mg/l), 1 (0.32 mg/l), and 4 (0.14 mg/l) (Table 4). The NOx data was separated between main segment data and tributary data for EC Segment 1. It is evident that significant contributions are made in the tributary reach (Table 4). Interestingly, the mean concentration in EC Segment 3 is higher than the mean concentrations for NOx in EC Segments 1 and 2, both direct contributors to EC Segment 3. More investigation is needed to determine if the majority of NOx observed in EC Segment 3 is contributed directly from upstream in EC Segments 1 and 2. The mean NOx concentration is significantly lower in EC Segment 4, indicating a sink (perhaps nutrient uptake or deposition of sediment in the stream). 34
Segment 1 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14975 Detections 14975 Non-Detects Approximate Location 16017 Detections 16017 Non-Detects Screening Level 3.0 Segment 1 Tributary Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16453 Detections 16453 Non-Detects Approximate Location 17478 Detections 17478 Non-Detects Screening Level Figure 17. EC Segment 1 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations. 35
3.0 Segment 2 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15834 Detections 15834 Non-Detects Approximate Location 17953 Detections 17953 Non-Detects 17954 Detections 17954 Non-Detects Screening Level Figure 18. EC Segment 2 Lilly Creek in the Little Cypress Creek Basin Total Nitrite-Nitrate (NOx) Concentration Observations 36
Segment 3 Main Channel Total Nitrate 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10333 Detections 10334 Detections Approximate Location 10335 Detections 16861 Detections 16861 Non-Detects Screening Level 3.0 Segment 3 Tributary Total Nitrate 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10279 Detections 10280 Detections Approximate Location 18590 Detections 18590 Non-Detects Screening Level Figure 19. EC Segment 3 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations 37
Segment 4 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10331 Detections 10332 Detections Approximate Location 10332 Non-Detects 15773 Detections 15773 Non-Detects Screening Level Segment 4 Tributary Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16532 Detections 16532 Non-Detects Approximate Location Screening Level Figure 20. EC Segment 4 Little Cypress Creek Total Nitrite-Nitrate (NOx) Concentration Observations 38
3.5 OTHER PARAMETERS OF INTEREST Caddo Lake Watershed Protection Plan Orthophosphorus (OP) measurements in the Little Cypress Creek Basin were well below the stream screening criteria limit of 0.37 mg/l based on the mean concentrations in EC Segments 1, 2, and 4. EC Segment 3 has a much higher mean concentration at 0.19 mg/l (0.10 mg/l when outliers are removed) compared to the other segments of this basin. Although these average concentrations are below the criteria, the OP measurements in the main channel in Segments 1, 3 and 4 are high enough to provide excess phosphorus to the river system to produce algal growth (based on analysis of chlorophyll-a in these segments). 39
Figure 21. Orthophosphate Concentrations for EC Segment 1 40
Figure 22. Orthophosphate Concentrations for EC Segment 2 41
Figure 23. Orthophosphate Concentrations for EC Segment 3 42
Figure 24. Orthophosphate Concentrations for EC Segment 4 43
Chlorophyll-a concentrations were measured in all four segments within the Little Cypress Creek Basin. The highest mean concentrations are in EC Segment 1 (12.76 µg/l) followed by segments 2 (8.14 µg/l), 3 (6.34 µg/l), and 4 (4.85 µg/l). Mean concentrations at all of these segments were below the stream criteria for chlorophyll-a (14.1 µg/l). When the tributary stations are separated from the main channel for segment 1, the tributary stations indicate an impedance due to elevated chlorophyll-a with a mean of 14.66 µg/l. Further examination of the segments by station provides insight into the source locations of nutrients that provide sufficient food sources for algal growth. In EC Segment 1, 24.4% of the 66 samples exceeded the screening criteria. Station 17478, the downstream tributary station on Kelsey Creek (Figure 3), was monitored 26 times between Oct 2001 and Feb 2008, during which 11 measured concentrations exceeded the screening criteria indicating a relevant issue for chlorophyll-a in this area. Station 16453, located upstream of 17478 along Kelsey Creek (Figure 3), had only 5 samples (fewer than the minimum 10 samples for analyses), but did indicate elevated levels of chlorophyll-a. Station 16017, located the furthest downstream on EC Segment 1, was monitored 10 times with three exceedances above the screening criteria. Station 14975, the furthest upstream station in EC Segment 1, was monitored 25 times (mostly between Oct 2000 and July 2006) and had only one measured chlorophyll-a concentration above the screening criteria. A total of 40 measured chlorophyll-a concentrations were taken in EC Segment 2 (Table 4) and only 12.5% of the measurements exceeded the screening criteria. At station 17954, however, 3 of the 9 samples in the entire period of record (Oct 2003 and May 2006) were above the screening criteria. In EC Segment 3, the number of chlorophyll-a samples varied by station. Only three of the ten stations had more than 10 samples (stations 10334, 10335, and 16861). These stations did not indicate any relevant issues for chlorophyll-a though some elevated concentrations were observed. In EC Segment 4, only two out of the four stations had plentiful data (> 10 samples) for analyses and the stations with enough data did not signify any relevant issues though some elevated concentrations were observed. 44
Segment 1 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14975 Detections 14975 Non-Detects Approximate Location 16017 Detections 16017 Non-Detects Screening Level 200 Segment 1 Tributary Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16453 Detections 16453 Non-Detects Approximate Location 17478 Detections 17478 Non-Detects Screening Level Figure 25. Chlorophyll-a Concentrations for EC Segment 1 45
200 Segment 2 Main Channel Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15834 Detections 15834 Non-Detects Approximate Location 17953 Detections 17953 Non-Detects 17954 Detections 17954 Non-Detects Screening Level Figure 26. Chlorophyll-a Concentrations for EC Segment 2 200 Segment 3 Main Channel Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1980 1985 1990 1995 2000 2005 2010 10333 Detections 10333 Non-Detects 10334 Detections 10334 Non-Detects Approximate Location 10335 Detections 10335 Non-Detects 16861 Detections 16861 Non-Detects Screening Level 46
200 Segment 3 Tributary Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10279 Detections 10279 Non-Detects Approximate Location 10280 Detections 14996 Detections 16533 Detections 16533 Non-Detects 18590 Non-Detects Screening Level Figure 27. Chlorophyll-a Concentrations for EC Segment 3 47
Segment 4 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10331 Non-Detects 10332 Detections Approximate Location 10332 Non-Detects 15773 Detections 15773 Non-Detects Screening Level Segment 4 Tributary Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 16532 Detections 16532 Non-Detects Approximate Location Screening Level Figure 28. Chlorophyll-a Concentrations for EC Segment 4 48
3.6 TREND ANALYSIS - ph Caddo Lake Watershed Protection Plan Trend analysis is a quantitative assessment tool used to determine whether or not the values of a parameter are increasing or decreasing over time and to provide an estimate of the rate of change. Data for ph appear to have a slightly increasing trend in EC Segment 2, while ph appears to be stable in segments 2, 3 and 4 (Figure 29). Segment 1 ph is higher than any of the other segments. The mean value in Segments 2, 3 and 4 is between 6.0 and 6.5. These trends are encouraging and indicate that further investigation is not warranted at this time. 3.7 TREND ANALYSIS - DO EC Segment 1 DO concentrations indicate a slightly increasing trend (Figure 30). EC Segment 2, however, indicates a declining trend in DO (Figure 30). It should be noted that EC Segment 2, Lilly Creek, has the highest relative impediment in the Little Cypress Creek for bacteria as well as elevated nutrient (TP and NOx) concentrations compared to other segments. The increased pollutant loadings appear to be having an adverse affect on the DO and water quality in EC Segment 2. EC Segment 3 DO observations (Figure 30) indicate depressed DO concentrations in the early 1990 s and improved DO on average in recent years. The trend for DO concentrations in EC Segment 4 have experienced a slight decline and increased variability (Figure 30). Segments 3 and 4 do have individual DO measurements that are significantly lower than 7 mg/l and could be a relevant issue. 49
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 1 - ph Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 2 - ph 9.000 8.000 7.000 6.000 5.000 9.000 8.000 7.000 6.000 5.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 4.000 3.000 2.000 1.000 0.000 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 1.000 0.000 7/24/1998 8/11/1987 12/6/1999 4/19/2001 9/1/2002 1/14/2004 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 3 - ph 5/7/1990 1/31/1993 5/28/2005 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 10/28/1995 7/24/1998 Date 4/19/2001 10/10/2006 1/14/2004 2/22/2008 10/10/2006 7/6/2009 7/6/2009 4.000 3.000 2.000 1.000 0.000 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 1.000 0.000 Figure 29. ph Trends for Little Cypress Creek 2/9/1999 10/28/1972 6/23/2000 11/5/2001 Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 4 - ph 4/20/1978 10/11/1983 3/20/2003 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 4/2/1989 9/23/1994 8/1/2004 3/15/2000 12/14/2005 9/5/2005 50
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 1 Main Stations - Daytime DO Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 2 - DO Dissolved Oxygen (mg/l) 18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000 2.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response Dissolved Oxygen (mg/l) 14.000 12.000 10.000 8.000 6.000 4.000 2.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 0.000 7/24/1998 12/6/1999 4/19/2001 9/1/2002 1/14/2004 Date 5/28/2005 10/10/2006 2/22/2008 7/6/2009 0.000 7/24/1998 12/6/1999 4/19/2001 9/1/2002 Date 1/14/2004 5/28/2005 10/10/2006 Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 3 - DO Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 4 - DO Dissolved Oxygen (mg/l) 14.000 12.000 10.000 8.000 6.000 4.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response Dissolved Oxygen (mg/l) 18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 2.000 2.000 0.000 0.000 8/11/1987 5/7/1990 1/31/1993 10/28/1995 7/24/1998 Date 4/19/2001 1/14/2004 10/10/2006 7/6/2009 3/8/1971 8/28/1976 Figure 30. DO Trends for Little Cypress Creek Basin 2/18/1982 8/11/1987 Date 1/31/1993 7/24/1998 1/14/2004 51
Table 4. Summary Statistics by Segment for the Little Cypress Creek EC Segment 1 2 3 4 NH 3 NOx Ortho Chloro FC A E. coli A Parameter DO (mg/l) ph (mg/l) (mg/l) TP (mg/l) (mg/l) (u g/l) (#/100mL) (#/100mL) Screening Criteria > 5.0 5.5-8.5 0.33 2.76 0.69 0.37 14.1 < 200 < 126 Mean 6.56 6.92 0.11 0.36 0.10 0.04 10.49 73.56 20.32 Median 7.40 6.90 0.03 0.19 0.07 0.03 5.00 73.00 38.00 Maximum 11.70 8.90 1.70 1.29 0.66 0.34 80.00 830.00 4800.00 Minimum 0.00 5.30 0.03 0.02 0.01 0.01 0.50 6.00 0.50 25th Perc 5.50 6.60 0.03 0.05 0.03 0.02 5.00 28.50 1.00 n 200 201 66 24 66 65 51 10 47 Mean 5.03 6.35 0.19 0.33 0.21 0.01 8.14 25.06 278.74 Median 4.80 6.40 0.13 0.25 0.17 0.01 1.65 29.50 253.20 Maximum 12.10 8.10 0.85 1.02 0.83 0.05 59.00 442.00 4838.00 Minimum 0.40 4.90 0.01 0.02 0.01 0.01 1.00 0.50 7.40 25th Perc 3.00 6.10 0.08 0.06 0.04 0.01 1.00 18.00 184.70 n 75 81 41 40 41 21 21 22 19 Mean 5.34 6.49 0.12 0.56 0.28 0.19 6.34 114.30 151.11 Median 4.70 6.60 0.06 0.21 0.19 0.05 4.50 124.50 99.00 Maximum 12.70 7.60 4.24 9.26 7.06 6.77 64.00 1600.00 2419.00 Minimum 0.60 3.30 0.01 0.02 0.01 0.01 0.50 5.00 10.00 25th Perc 4.11 6.27 0.03 0.13 0.11 0.03 2.00 66.00 74.00 n 189 192 91 48 101 95 72 36 29 Mean 6.76 6.55 0.06 0.13 0.12 0.04 4.85 74.87 120.57 Median 6.40 6.50 0.04 0.10 0.09 0.03 3.56 83.50 125.00 Maximum 16.40 8.60 0.90 0.40 1.34 0.33 40.70 2000.00 2419.00 Minimum 0.70 5.10 0.01 0.02 0.01 0.01 0.50 5.00 3.00 25th Perc 5.10 6.30 0.03 0.09 0.06 0.02 0.75 50.00 58.25 n 286 287 235 104 240 135 79 50 34 52
EC Segment 1 Main Reach Ortho (mg/l) Main Reach E. coli (MPN/100 ml) Tributary E. coli (MPN/100 ml) Main Reach DO Tributary Main Tributary Main NOx Tributary NOx Main Reach TP Tributary Tributary Ortho Main Reach Tributary Chloro Parameter (mg/l) DO (mg/l) Reach ph ph (mg/l) (mg/l) (mg/l) TP (mg/l) (mg/l) Chloro (ug/l) (ug/l) Screening Criteria > 5.0 > 5.0 5.5-8.5 5.5-8.5 2.76 2.76 0.69 0.69 0.37 0.37 14.1 14.1 < 126 < 126 Mean 7.98 6.28 6.54 7.00 0.44 0.18 0.15 0.05 0.06 0.02 9.83 14.66 259.62 1.77 Median 8.4 7.3 6.65 6.9 0.4 0.07 0.11 0.03 0.03 0.02 5 10.7 147.00 1.00 Maximum 11.6 11.7 7.5 8.9 1.075 1.29 0.66 0.1 0.34 0.03 80 71.4 4800.00 270.00 Minimum 2.3 0 5.7 5.3 0.02 0.02 0.005 0.016 0.005 0.005 0.5 1 38.00 0.50 25th Perc 6.4 4.95 6.2 6.6 0.164 0.03025 0.07 0.025 0.03 0.02 5 5 120.00 0.50 n 33 167 34 167 34 30 35 31 34 31 35 55 23 24 A denotes geometric mean NS denotes Not Sampled 53
4.0 BIG CYPRESS CREEK BASIN DATA AND TREND ANALYSIS The Big Cypress watershed was subdivided into nine EC Segments (Segments 5 through 13). The Segments can be seen for the entire watershed in Figure 1. As can be seen in Figure 31, Segments 5, 7, and 8 are the upper segments in the Big Cypress watershed. EC Segment 10 (Big Cypress Bayou) is downstream of EC Segments 5 (Black Cypress Bayou) and Segment 6 (Big Cypress Bayou upstream of Black Cypress Bayou, downstream of Lake O'Pines) (Figure 32). EC Segment 9 (Haggerty Creek) also contributes to EC Segment 10 after the confluence of Black Cypress Bayou (EC Segment 5) and Big Cypress Bayou (EC Segment 6) (Figure 1). Upstream of Lake O Pines was not evaluated since a TMDL has already been completed with an Implementation Plan underway for this portion of the Cypress Creek Basin. EC Segments 7 (Jim Bayou) and 8 (Frazier Creek) join to form James Bayou (EC Segment 12) which then contributes to Caddo Lake (Figure 31). EC Segment 11 (Kitchen Creek) and EC Segment 13 (Harrison Bayou) feed directly into Caddo Lake (Figure 32). SWQM stations in the Big Cypress watershed are also shown in Figure 31 and Figure 32. 15000 18201 15137 16934 15838 8 10248 16258 14474 5 10247 16936 16935 10246 16705 10328 10256 10326 15000 10325 10327 10324 10254 10323 10244 7 10255 18200 10259 10322 10321 10320 10257 11 14976 10258 10319 10260 12 14999 10245 10243 15000 14998 Figure 31. SWQM Station Locations for EC Segments 5, 7, 8, 11, and 12. 54
5 11 12 13973 13630 15135 6 15511 10332 13136 10331 10 16254 15020 14471 15510 15248 10295 16253 15021 15022 16365 15134 15182 16532 15773 4 15001 10250 14997 9 13 15506 15509 15508 15507 4.1 BACTERIA Figure 32. SWQM Station Locations for EC Segments 4, 5, 6, 9, 10, 11, 12 and 13. None of the segments contributing to and including EC Segment 10 are impeded for bacteria based on the geometric mean (Table 5). The highest average concentrations for fecal coliform for this branch of the Big Cypress Bayou are in EC Segment 5 followed by segments 6, 10-Main Channel (M), 10-Headwater (HW), and not measured in Segment 9. For E. coli the EC Segment 6 had the highest values followed by 5, 9, 10-M, and 10-HW. There are not enough grab sample exceedances in EC Segments 5, 6, or 10 to consider bacteria to be a primary impediment. In addition, not enough data were collected in EC Segment 9 for analyses only four E. coli samples at one station and zero fecal coliform samples were taken in this segment. Even though the bacteria measurements were generally under the criteria in these segments, sources of bacteria occur in many of these segmented sub-watersheds (see Section 6.4 of this report). 55
10000 Segment 5 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 10243 Detections 2007 2008 2009 2010 10245 Detections Approximate Location 10247 Detections 10248 Detections 16705 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 5 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10243 Detections 10244 Detections 10245 Detections 10245 Non-Detects 10246 Detections 10247 Detections 10247 Non-Detects 10248 Detections 16705 Detections Grab Sample Criteria Geomean Criteria Approximate Location 56
Segment 5 Tributary Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14474 Detections 16934 Detections Approximate Location 16935 Detections 16936 Detections Grab Sample Criteria Geomean Criteria Figure 33. Bacteria Concentrations for EC Segment 5. 10000 Segment 6 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15511 Detections Approximate Location Grab Sample Criteria Geomean Criteria 57
Segment 6 Main Channel Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15135 Detections 15511 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 34. Bacteria Concentrations for EC Segment 6. Segment 9 Main Channel E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 14997 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 35. Bacteria Concentrations for EC Segment 9. 58
10000 Segment 10 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 15022 Detections 2007 2008 2009 2010 15022 Non-Detects Approximate Location 16254 Detections 16254 Non-Detects Grab Sample Criteria Geomean Criteria 10000 Segment 10 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10295 Detections 10295 Non-Detects 14471 Detections 14471 Non-Detects 15022 Detections 16254 Detections 16254 Non-Detects Grab Sample Criteria Geomean Criteria Approximate Location 59
Segment 10 Lake Headwaters Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10294 Detections 10294 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Figure 36. Bacteria Concentrations for EC Segment 10. EC Segment 7, Jim s Bayou, can be considered impeded due to bacteria (specifically E. coli) readings with a geomean of 153 MPN/100mL (Table 5) but not on the basis of grab samples where only 24% exceed the grab sample limit (Appendix B Segment 7). Only one station (See Figure 31 for location) has enough data for individual station analyses, 10321, which does not exceed the allowed percentage of grab samples above the criteria. Stations 10256 and 14976 (the most recent data available) have more than 25% of samples elevated above the grab sample criteria but not enough data has been collected to identify a primary impediment on this basis. Bacteria data should be collected along EC Segment 7 in future efforts based on this evidence. EC Segments 8 and 12 do not have bacteria impairments based on the historic data for fecal coliform. Not enough E. coli data has been collected in either of these segments to make any conclusions. Monitoring of EC Segment 12 for bacteria is recommended to determine if bacteria in EC Segment 7 is impacting the downstream reach. 60
10000 Segment 7 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10321 Detections Approximate Location 14976 Detections Grab Sample Criteria Geomean Criteria 10000 Segment 7 Tributary E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10256 Detections Approximate Location Grab Sample Criteria Geomean Criteria 61
Segment 7 Main Channel Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1980 1985 1990 1995 2000 2005 2010 10321 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 37. Bacteria Concentrations for EC Segment 7. 10000 Segment 8 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 17619 Detections Approximate Location Grab Sample Criteria Geomean Criteria 62
10000 Segment 8 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1980 1985 1990 1995 2000 2005 2010 10259 Detections 10259 Non-Detects Approximate Location 17619 Detections Grab Sample Criteria Geomean Criteria Figure 38. Bacteria Concentrations for EC Segment 8. 10000 Segment 12 Main Channel Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10319 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 39. Bacteria Concentrations for EC Segment 12. 63
EC Segment 11, Kitchen Creek, is a direct contributor to Caddo Lake (Figure 1). This segment has a geometric mean above the standard limit for E. coli (Table 5) but only three samples have been taken for E. coli and none for fecal coliform. These elevated readings are reason to continue monitoring bacteria concentrations in EC Segment 11. EC Segment 13, Harrison Bayou, monitoring of E. coli in the main reach indicates a geomean (Table 5) of 161 MPN/100 ml (above the standard limit) based on eight samples at station 15508 (Appendix B Segment 13) and has the second highest 25 th percentile compared to the other segments (Table 5). More bacteria data should be collected in this segment as well based on this evidence. Much more data has been collected in EC Segment 13 at the headwaters of Caddo Lake at station 10286. These data do not indicate any impairment for bacteria in EC Segment 13 at the headwaters of Caddo Lake, but this station should continue to be monitored due to the elevated concentrations observed upstream and reported exceedances above the grab sample limit. 10000 Segment 11 Main Channel E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 14998 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 40. Bacteria Concentrations for EC Segment 11. 64
Segment 13 Main Channel E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15508 Detections Approximate Location Grab Sample Criteria Geomean Criteria 10000 Segment 13 Lake Headwaters E. Coli 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10286 Detections 10286 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria 65
10000 Segment 13 Lake Headwaters Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10286 Detections Approximate Location 10286 Non-Detects Grab Sample Criteria Geomean Criteria Figure 41. Bacteria Concentrations for EC Segment 13. 4.2 TOTAL PHOSPHORUS EC Segment 9 had the highest mean TP concentration (Table 5) out of all the segments analyzed, but only eight samples (four at each station with no overlap in sampling time period) were taken and all were still below the stream criteria for TP. Continued monitoring of TP in EC Segment 9 is highly recommended because of its close proximity to Caddo Lake and because the average concentration exceeds the reservoir criteria. The next highest mean TP concentration for the Big Cypress Bayou branch is found in EC Segment 5 followed by segments 10 and 6, respectively, (Table 5) all of which fell well below both the stream and reservoir criteria (Appendix B). However, there is enough phosphorus in these segments to produce algal growth, especially in a lake environment (North Carolina State University, 2008), as indicated by the observed concentrations of chlorophyll-a representing the presence of algae. 66
Figure 42. Total Phosphorus Concentrations in EC Segment 5. 67
Figure 43. Total Phosphorus Concentrations in EC Segment 6. Figure 44. Total Phosphorus Concentrations in EC Segment 9. 68
Figure 45. Total Phosphorus Concentrations in EC Segment 10. For EC Segment 7 TP data were not collected in large quantities except at station 10321 (Appendix B Segment 7). These data did not indicate any impediment for TP based on the stream criteria (Table 5), but 69
this segment should continue to be monitored since TP in this segment appears to have an upward trend and does provide enough phosphorus for algal growth as indicated by measured concentrations of chlorophyll-a. EC Segment 8 had an even lower mean TP concentration than EC Segment 7 and again only had one station with sufficient data collection (station 10259) indicating no cause for distress. EC Segment 12 also only has one station with sufficient monitoring for analyses (station 10319). The data indicate values lower than the standard, but with an increasing trend in recent years. Monitoring should be continued at Segment 12 to determine if the increasing trend still exists. 70
Figure 46. Total Phosphorus Concentrations in EC Segment 7. 71
Figure 47. Total Phosphorus Concentrations in EC Segment 8. 72
Figure 48. Total Phosphorus Concentrations in EC Segment 12. A total of seven TP readings were taken in EC Segment 11 with no exceedances above the screening criteria and the mean value does not indicate an impediment for TP (Table 5). A total of 24 TP samples were taken in the main reach of EC Segment 13 with only one exceedance above the stream screening criteria (Appendix B EC Segment 13) and an average well below the stream screening criteria (Table 5). The reservoir screening criteria was applied to EC Segment 13 at the headwaters to Caddo Lake. The average was above the criteria in this area of the segment (Table 5), but only six samples were taken. Phosphorus monitoring should continue at the headwaters as well as upstream to help determine the source of the phosphorus loading and if in fact a relevant issue exists. 73
Figure 49. Total Phosphorus Concentrations in EC Segment 11. 74
Figure 50. Total Phosphorus Concentrations in EC Segment 13. 4.3 AMMONIA The historic ammonia concentrations were plotted against the screening criteria (Figure 51, Figure 52, Figure 53, and Figure 54) for EC Segments 5, 6, 9, and 10. None of these segments indicate a relevant issue based on the stream criteria for ammonia. The highest average concentration is found in EC Segment 9 (0.12 mg/l) followed by EC Segments 5, 6, 10-M, and 10 at the headwaters to Caddo Lake respectively (Table 5). 75
Figure 51. EC Segment 5 Black Cypress Creek Ammonia Observations. 76
Figure 52. EC Segment 6 Big Cypress Creek Ammonia Observations. Figure 53. EC Segment 9 Haggerty Creek Ammonia Observations. 77
Figure 54. EC Segment 10 Big Cypress Bayou Ammonia Observations. Ammonia concentrations were plotted against the screening criteria (Figure 55, Figure 56, and Figure 57) for EC Segments 7, 8, and 12. None of these segments indicate a relevant issue based on the stream criteria for ammonia. The highest average concentration is found in EC Segment 8 (0.13 mg/l) followed 78
by EC Segments 7 (0.12 mg/l), and 12 (0.06 mg/l), respectively (Table 5). The higher concentrations of ammonia in segments 7 and 8 are reduced in Segment 12. This reduction is primarily caused by the breakdown of ammonia (NH 3 ) into other forms of nitrogen, primarily NO 2 and NO 3 (NOx), which then becomes readily available for plant uptake (Symons, 1997). 79
Figure 55. EC Segment 7 Jim Bayou Ammonia Observations. Figure 56. EC Segment 8 Frazier Creek Ammonia Observations. 80
Figure 57. EC Segment 12 James Bayou Ammonia Observations. Ammonia concentrations for EC segments 11 and 13, direct contributors to Caddo Lake, were plotted against the screening criteria (Figure 58 and Figure 59). The only area indicating water quality is impeded by ammonia is in EC Segment 13 at the headwaters to Caddo Lake where the mean concentration is 81
above the reservoir criteria. The observed exceedances occurred between 1998 and 2000 and samples for ammonia in this region have not been taken since that time period. Figure 58. EC Segment 11 Kitchen Creek Ammonia Observations. 82
Figure 59. EC Segment 13 Harrison Bayou Ammonia Observations. 83
4.4 NITRITE-NITRATE (NOx) Caddo Lake Watershed Protection Plan The highest average total NOx for the Big Cypress Bayou branch of the basin is in EC Segment 10-M and 5, followed by EC Segment 6 (Table 5). Additional NOx contributions to EC Segment 10 could be from EC Segment 9 where the data is limited (4 samples). None of these samples in this portion of the basin exceed the stream criteria (Table 5) for NOx indicating no impediment for nitrogen oxides. A total of 16 samples were taken in Segment 10 at the headwaters of Caddo Lake and this data indicates NOx is not a relevant issue in this area. 3.0 Segment 5 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 10243 Detections 2000 10243 Non-Detects 2005 2010 10244 Detections 10244 Non-Detects 10245 Detections 10245 Non-Detects Approximate Location 10246 Detections 10246 Non-Detects 10247 Detections 10247 Non-Detects 10248 Detections 10248 Non-Detects 16705 Detections 16705 Non-Detects Screening Level 84
3.0 Segment 5 Tributary Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14474 Detections 14474 Non-Detects 16934 Detections 16934 Non-Detects Approximate Location 16935 Detections 16935 Non-Detects 16936 Detections 16936 Non-Detects Screening Level Figure 60. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 5. 3.0 Segment 6 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 13630 Detections 13630 Non-Detects Approximate Location 15135 Detections 15135 Non-Detects 15511 Detections 15511 Non-Detects Screening Level Figure 61. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 6. 85
Segment 9 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 14997 Detections 14997 Non-Detects Approximate Location Screening Level Figure 62. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 9. 86
Segment 10 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10295 Detections 10295 Non-Detects 14471 Detections 14471 Non-Detects Approximate Location 16254 Detections 16254 Non-Detects Screening Level Segment 10 Lake Headwaters Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10294 Detections 10294 Non-Detects Approximate Location Screening Level Figure 63. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 10. 87
EC Segments 7, 8, and 12 do not pose any impediment for NOx based on the average concentration compared to the stream criteria (Table 5). EC Segment 7 has the highest average NOx concentration followed by EC Segments 8 and 12 respectively (Table 5). 3.0 Segment 7 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 10320 Detections 2000 10320 Non-Detects 2005 2010 10321 Detections 10321 Non-Detects 10322 Detections 10322 Non-Detects Approximate Location 10323 Detections 10323 Non-Detects 10324 Detections 10324 Non-Detects 10325 Detections 10325 Non-Detects 10326 Detections 10326 Non-Detects 10327 Detections 10327 Non-Detects 10328 Detections 10328 Non-Detects 14976 Detections 14976 Non-Detects Screening Level 3.0 Segment 7 Tributary Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10254 Detections 10254 Non-Detects 10255 Detections 10255 Non-Detects Approximate Location 10256 Detections 10256 Non-Detects 10257 Detections 10257 Non-Detects Screening Level Figure 64. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 7. 88
3.0 Segment 8 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10258 Detections 10258 Non-Detects Approximate Location 10259 Detections 10259 Non-Detects 17619 Detections 17619 Non-Detects Screening Level Figure 65. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 8. 89
Segment 12 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10319 Detections 10319 Non-Detects Approximate Location Screening Level Segment 12 Tributary Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10260 Detections 10260 Non-Detects Approximate Location Screening Level Figure 66. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 12. 90
Total nitrite-nitrate nitrogen (NOx) data was limited (see Appendix B) in EC Segments 11 and 13 (both along the main reach and at the headwaters). Additional data should be collected to determine if NOx is a relevant issue in these regions and if these segments are contributing excess loading to Caddo Lake. 3.0 Segment 11 Main Channel Nitrate plus Nitrite 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 14998 Detections 14998 Non-Detects Approximate Location Screening Level Figure 67. Total Nitrite-Nitrate Nitrogen (NOx) Concentartions in EC Segment 11 91
Segment 13 Main Channel Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15508 Detections 15508 Non-Detects Approximate Location Screening Level Figure 68. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in EC Segment 13. 4.5 OTHER PARAMETERS OF INTEREST Limited orthophosphate data was collected in EC Segments 9 (four samples at one station) and did not indicate a concern in EC Segments 5, 6, or 10 (both on the main reach and at the headwaters to Caddo Lake) (Table 5). Chlorophyll-a concentrations is this region of the basin do raise some issues. Approximately 19% of the samples at station 10246 (near Pruitt Lake) in Segment 5 exceed the screening level (Appendix B) and monitoring should resume (period of record ends in Oct 2004). This section of the Black Bayou is listed as a concern for use attainment due to chlorophyll-a according to the DRAFT 2008 Texas Water Quality Inventory. EC Segment 9 has a mean concentration above the screening criteria for chlorophyll-a (Table 5) with three out of eight samples exceeding the screening criteria (Appendix B Segment 9). More data should be collected in this reach to determine if a relevant issue exists for chlorophyll-a in this segment. The remaining segments had enough data to conclude that chlorophyll-a is not a relevant issue (Table 5). 92
Figure 69. Orthophosphate Concentrations in EC Segment 5. 93
Figure 70. Orthophosphate Concentrations in EC Segment 6. Figure 71. Orthophosphate Concentrations in EC Segment 10. 94
200 Segment 5 Main Channel Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1970 1975 1980 1985 1990 10243 Detections 1995 10243 Non-Detects 2000 2005 2010 10244 Detections 10245 Detections Approximate Location 10245 Non-Detects 10246 Detections 10246 Non-Detects 10247 Detections 10247 Non-Detects 10248 Detections 10248 Non-Detects 16705 Detections 16705 Non-Detects Screening Level 200 Segment 5 Tributary Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14474 Non-Detects 16934 Detections Approximate Location 16934 Non-Detects 16935 Detections 16935 Non-Detects 16936 Non-Detects Screening Level Figure 72. Chlorophyll-a Concentrations in EC Segment 5. 95
Segment 6 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 13630 Detections 15135 Detections Approximate Location 15135 Non-Detects 15511 Detections 15511 Non-Detects Screening Level Figure 73. Chlorophyll-a Concentrations in EC Segment 6. 200 Segment 9 Main Channel Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14997 Detections 14997 Non-Detects Approximate Location 16253 Detections 16253 Non-Detects Screening Level Figure 74. Chlorophyll-a Concentrations in EC Segment 9. 96
Segment 10 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10295 Detections 10295 Non-Detects 14471 Detections 14471 Non-Detects Approximate Location 15022 Detections 15022 Non-Detects 16254 Detections 16254 Non-Detects Screening Level Segment 10 Lake Headwaters Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10294 Detections 10294 Non-Detects Approximate Location Screening Level Figure 75. Chlorophyll-a Concentrations in EC Segment 10. 97
Orthophosphate does not pose any current relevant issues pertaining to adverse water quality for the James Bayou (EC Segment 12) or contributing reaches (EC Segments 7 and 8) based on the screening criteria and data trends. A sufficient number of samples to support analyses of chlorophyll-a concentrations has been collected at station 10321 in EC Segment 7, station 10259 in EC Segment 8, and at station 10319 in EC Segment 12 (Appendix A). Segments 8 and 12 have several values over the screening criteria and should continue to be monitored for algal growth (chlorophyll-a). 98
200 Segment 7 Main Channel Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1980 1985 1990 1995 10320 Non-Detects 2000 10321 Detections 2005 2010 10321 Non-Detects 10322 Non-Detects Approximate Location 10323 Detections 10324 Detections 10325 Detections 10326 Non-Detects 10327 Detections 10328 Detections 14976 Detections 14976 Non-Detects Screening Level 200 Segment 7 Tributary Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1980 1985 1990 1995 2000 2005 2010 10254 Non-Detects 10255 Detections Approximate Location 10256 Detections 10257 Detections Screening Level Figure 76. Chlorophyll-a Concentrations in EC Segment 7. 99
Segment 8 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1980 1985 1990 1995 2000 2005 2010 10258 Detections 10259 Detections Approximate Location 10259 Non-Detects 17619 Detections 17619 Non-Detects Screening Level Figure 77. Chlorophyll-a Concentrations in EC Segment 8. Figure 78. Chlorophyll-a Concentrations in EC Segment 12. 100
Figure 79. Orthophosphate Concentrations in EC Segment 7. 101
Figure 80. Orthophosphate Concentrations in EC Segment 8. 102
Figure 81. Orthophosphate Concentrations in EC Segment 12. Limited orthophosphate data has been collected for EC Segments 11 and none in EC Segment 13 at the headwaters of Caddo Lake. Data collected for EC Segment 13 in the main reach does not indicate any reason for distress for OP based on the criteria; however, continued monitoring should be conducted to evaluate OP trends. EC Segment 11 has only been sampled for chlorophyll-a on seven occasions, but has an average (12.1 µg/l) close to the screening criteria (Table 5) and should be monitored in the future. EC Segment 13 in the main reach has sufficient data collection for chlorophyll-a and does not indicate any cause for distress. The headwaters to Caddo Lake in EC Segment 13 have been sampled six times with a mean concentration above the reservoir screening criteria (Table 5) indicating a need for resumed monitoring (period of record ends in 1999). 103
Figure 82. Orthophosphate Concentrations in EC Segment 11. Figure 83. Orthophosphate Concentrations in EC Segment 13. 104
Segment 11 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14998 Detections 14998 Non-Detects Approximate Location Screening Level Figure 84. Chlorophyll-a Concentrations in EC Segment 11. 105
Segment 13 Main Channel Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15507 Detections 15507 Non-Detects Approximate Location 15508 Non-Detects 15509 Detections 15509 Non-Detects Screening Level 200 Segment 13 Lake Headwaters Chlorophyll-a 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 10286 Detections 10286 Non-Detects Approximate Location Screening Level Figure 85. Chlorophyll-a Concentrations in EC Segment 13. 106
4.6 TREND ANALYSIS - ph Caddo Lake Watershed Protection Plan The trend plot for ph (Figure 86) in EC Segment 5 shows some decline from mid 1970 s to mid 1980 s and then stabilized between the mid 1980s until currently with an average ph value around 6.0 during the last two decades. However, these data are highly variable between stations and several values are below the lower limit of 6.0. Continued monitoring is recommended along this segment to determine if ph is declining. EC Segment 6 ph measurements show (Figure 86) a stable ph with an average of 6.79 for the entire period of record (1983 2008). The limited data available at EC Segment 9 does show ph improvement (Figure 86) from the readings taken Jul 1998 to Apr 1999 to the more recent data taken between Oct 2005 and Aug 2006 (though it should be noted that the data was reported at different stations for the two time periods). The ph trend for EC Segment 10 along the main reach appears (Figure 86) stable over the period of record, Jul 1972 to Aug 2007, with an average ph value of 6.47. 107
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 5 - ph Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 6 - ph 10.000 9.000 8.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 9.000 8.000 7.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 7.000 6.000 5.000 4.000 3.000 2.000 1.000 0.000 3/8/1971 8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009 6.000 5.000 4.000 3.000 2.000 1.000 0.000 2/18/1982 11/14/1984 8/11/1987 5/7/1990 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006 7/6/2009 Date Date Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 10 Main Stations - ph 9.000 8.000 7.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 6.000 5.000 4.000 3.000 2.000 1.000 0.000 3/8/1971 8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009 Date Figure 86. ph Trends in the Big Cypress Bayou 108
Since 2001, EC Segments 7 and 8 have shown an upward trend in ph (Figure 87). Values of ph at station 10259 in EC Segment 8 are below the screening criteria range for 29.3% of the records (Appendix A) and should be monitored due to these concerns. EC Segment 12 has less data to make a strong conclusion about the trend but does not appear to have an adverse trend and the mean ph for the period of record is 6.26. 109
Figure 87. ph Values in EC Segment 7. 110
Figure 88. ph Values in EC Segment 8. Figure 89. ph Values in EC Segment 12. 111
A historic trend for ph in EC Segment 11 cannot be determined because of limited data as well as a large data gap (Figure 90) in the period of record. All of the reported data fall within the standard criteria limits for ph in EC Segment 11. A slightly increasing historic trend for ph values has occurred in EC Segment 13 (Figure 91) along the main channel. In addition, all of the historic data in EC Segment 13 meet the standard criteria for ph in all observations. EC Segment 13 at the headwaters to Caddo Lake has a lower average ph compared to the main channel. Figure 90. ph Values in EC Segment 11. 112
Figure 91. ph Values in EC Segment 13. 113
4.7 TREND ANALYSIS - DO Caddo Lake Watershed Protection Plan DO in EC Segment 5 declined from 1972 until 1998, then began to rise in recent years, but with increased variability (Figure 92). EC Segment 6 has exhibited a rise in DO since the early 1980 s. Limited DO data have been collected in EC Segment 9 to make any trending conclusions. The Big Cypress Bayou (EC Segment 10) has shown increasing DO levels and appears to be sufficient for sustaining aquatic life. However, DO concentrations are decreasing in the portions of the segment in the headwaters of Caddo Lake, and much of the data collected at these stations were below the screening criteria. DO levels in all samples collected at station 10294 since 2005 have been below the screening level. DO monitoring should continue at this station to determine if the levels are continuing to decline. EC Segments 7, 8 and 12 do not have DO mean concentrations below the screening criteria for their respective periods of record and show direct trends (Figure 93) in all of the reaches. A further look at the records at individual stations does raise some cause for relative concern however. The downstream portion of EC Segment 7 (Figure 31), Jim Bayou, at stations 10321, 10320, and 14976 all indicate DO levels below the screening criteria 48 to 61% of the time (Appendix B Segment 7). The upstream stations have fewer records but do indicate a significant percentage of records below the standard; therefore, these stations should continue to be monitored. Beach Creek, station 10256, had elevated nutrients and bacteria as well as depressed DO for 58.3% of the records (Appendix B Segment 7). EC Segments 11 (Kitchen Creek) and 13 (Harrison Bayou) have experienced depressed DO at some stations with overall downward trends (Figure 94 and Figure 95). These segments should be monitored more extensively for DO. More NOx and TP monitoring is recommended to determine if increasing nutrient levels in these reaches are causing the lowered DO concentrations. 114
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 5 Main Stations - Daytime DO Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 6 Main Stations - DO 18.000 DO Linear Regression 20.000 DO Linear Regression Dissolved Oxygen (mg/l) 16.000 14.000 12.000 10.000 8.000 6.000 4.000 Confidence Interval for Mean Response Confidence Interval for Mean Response Dissolved Oxygen (mg/l) 18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000 Confidence Interval for Mean Response Confidence Interval for Mean Response 2.000 2.000 0.000 3/8/1971 8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009 0.000 2/18/1982 11/14/1984 8/11/1987 5/7/1990 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006 7/6/2009 Dissolved Oxygen (mg/l) 12.000 10.000 8.000 6.000 4.000 2.000 Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 9 Main Stations - DO DO Linear Regression Date Confidence Interval for Mean Response Confidence Interval for Mean Response Dissolved Oxygen (mg/l) 18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000 2.000 Date Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 10 Main Stations - Daytime DO DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 0.000 2/18/1982 11/14/1984 8/11/1987 5/7/1990 1/31/1993 10/28/1995 Date 7/24/1998 4/19/2001 1/14/2004 10/10/2006 7/6/2009 0.000 6/11/1968 12/2/1973 5/25/1979 11/14/1984 5/7/1990 Date 10/28/1995 4/19/2001 10/10/2006 115
Figure 92. DO Trends in the Big Cypress Bayou 116
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 7 - DO Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 8 - DO Dissolved Oxygen (mg/l) 14.000 12.000 10.000 8.000 6.000 4.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response Dissolved Oxygen (mg/l) 18.000 16.000 14.000 12.000 10.000 8.000 6.000 4.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 2.000 2.000 0.000 0.000 5/25/1979 11/14/1984 5/7/1990 10/28/1995 4/19/2001 10/10/2006 5/25/1979 11/14/1984 5/7/1990 10/28/1995 4/19/2001 10/10/2006 Date Date Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 12 - DO Dissolved Oxygen (mg/l) 16.000 14.000 12.000 10.000 8.000 6.000 4.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 2.000 0.000 9/15/1965 3/8/1971 8/28/1976 2/18/1982 8/11/1987 1/31/1993 7/24/1998 1/14/2004 7/6/2009 Date Figure 93. DO Trends in James Bayou (EC Segments 7, 8, and 12). 117
Figure 94. DO Concentrations in EC Segment 11. 118
Figure 95. DO Concentrations in EC Segment 13. 119
EC Segment 6 7 8 9 10-M 11 13-M Table 5. Big Cypress Creek Basin Summary Statistics by Segment Caddo Lake Watershed Protection Plan NH 3 NOx Ortho Chloro FC A E. coli A Parameter DO (mg/l) ph (mg/l) (mg/l) TP (mg/l) (mg/l) (u g/l) (#/100mL) (#/100mL) Screening Criteria > 5.0 6-8.5 0.33 2.76 0.69 0.37 14.1 < 200 < 126 Mean 9.02 6.79 0.08 0.08 0.05 0.02 5.27 59.29 110.52 Median 8.75 6.80 0.03 0.05 0.03 0.02 5.00 71.00 54.50 Maximum 18.50 7.90 0.60 0.59 0.61 0.16 39.20 420.00 2400.00 Minimum 3.60 5.80 0.01 0.02 0.01 0.00 0.50 3.00 11.00 25th Perc 7.20 6.50 0.03 0.02 0.03 0.01 1.65 32.25 33.50 n 160 130 107 63 108 81 48 14 24 Mean 5.02 6.47 0.12 0.17 0.15 0.05 10.24 77.96 153.07 Median 4.70 6.50 0.07 0.04 0.09 0.02 2.00 68.50 181.80 Maximum 12.90 7.90 1.61 1.66 0.85 0.63 270.00 7420.00 2000.00 Minimum 0.00 4.90 0.01 0.01 0.01 0.01 0.50 5.00 9.80 25th Perc 3.40 6.20 0.02 0.02 0.05 0.01 1.00 33.25 73.80 n 157 163 93 76 93 71 55 34 29 Mean 6.60 6.13 0.13 0.07 0.08 0.04 3.73 42.58 72.04 Median 6.20 6.01 0.09 0.06 0.05 0.01 1.00 50.00 79.75 Maximum 16.40 7.42 0.91 0.31 0.98 0.80 25.10 77400.00 127.70 Minimum 1.40 4.70 0.01 0.01 0.01 0.01 0.50 0.50 35.00 25th Perc 5.65 5.94 0.05 0.03 0.03 0.01 1.00 24.75 54.88 n 95 95 51 42 51 46 50 50 4 Mean 4.28 6.73 0.12 0.07 0.29 0.01 16.25 NS 72.55 Median 4.30 6.80 0.12 0.04 0.28 0.01 4.00 NS 103.80 Maximum 9.90 7.70 0.20 0.16 0.69 0.02 56.00 NS 191.80 Minimum 0.50 5.71 0.03 0.02 0.05 0.01 1.00 NS 15.00 25th Perc 1.66 6.53 0.05 0.02 0.09 0.01 2.28 NS 56.25 n 16 16 8 4 8 4 4 NS 4 Mean 6.90 6.46 0.06 0.08 0.09 0.03 7.18 25.26 20.86 Median 6.85 6.40 0.05 0.06 0.07 0.02 4.50 25.00 20.70 Maximum 16.40 8.10 0.40 0.62 0.85 0.62 55.00 1420.00 1413.60 Minimum 0.00 5.00 0.01 0.01 0.01 0.00 0.10 1.00 0.50 25th Perc 5.68 6.10 0.01 0.02 0.04 0.01 2.00 10.00 7.40 n 576 388 183 87 188 146 134 206 154 Mean 5.32 6.39 0.15 0.04 0.19 0.01 19.33 NS 232.05 Median 5.05 6.45 0.07 0.02 0.14 0.01 7.65 NS 88.00 Maximum 9.90 7.50 0.49 0.07 0.48 0.02 61.00 NS 2000.00 Minimum 0.56 5.80 0.01 0.02 0.05 0.01 1.00 NS 71.00 25th Perc 3.95 6.00 0.04 0.02 0.09 0.01 4.23 NS 79.50 n 14 14 7 3 7 4 4 NS 3 Mean 6.54 6.76 0.06 0.09 0.18 0.03 7.39 NS 161.14 Median 6.79 6.70 0.05 0.07 0.14 0.04 3.53 NS 124.60 Maximum 12.50 8.10 0.20 0.26 0.87 0.05 20.00 NS 730.00 Minimum 0.40 6.00 0.01 0.02 0.02 0.01 1.00 NS 25.00 25th Perc 4.39 6.60 0.01 0.06 0.11 0.02 2.80 NS 82.45 n 140 35 17 8 24 16 12 NS 8 NH 3 NOx Ortho Chloro FC A E. coli A EC Segment DO (mg/l) ph (mg/l) (mg/l) TP (mg/l) (mg/l) (u g/l) (#/100mL) (#/100mL) Screening Criteria > 4.0 6-8.5 0.33 2.76 0.69 0.37 14.1 < 200 < 126 Mean 7.42 6.23 0.08 0.08 0.10 0.04 5.63 63.38 97.39 Median 8.50 6.26 0.04 0.05 0.09 0.03 5.00 60.00 100.00 5 Maximum 16.30 8.60 1.80 0.34 0.44 0.15 87.90 36000.00 2400.00 Minimum 0.10 0.00 0.01 0.01 0.01 0.00 0.03 2.00 1.00 25th Perc 5.60 5.91 0.03 0.03 0.06 0.02 1.65 30.00 59.50 n 1057 1054 238 76 249 216 189 100 87 Mean 5.97 6.26 0.06 0.03 0.09 0.06 4.45 83.57 NS Median 6.00 6.20 0.05 0.02 0.05 0.01 2.00 90.00 NS 12 Maximum 15.10 7.40 0.36 0.11 1.21 1.21 31.00 1020.00 NS Minimum 0.10 5.30 0.01 0.01 0.01 0.01 1.00 10.00 NS 25th Perc 4.08 6.00 0.03 0.02 0.03 0.01 2.00 50.00 NS n 128 79 67 27 66 41 46 35 NS 120
NH 3 NOx Ortho Chloro FC A E. coli A EC Segment Parameter DO (mg/l) ph (mg/l) (mg/l) TP (mg/l) (mg/l) (u g/l) (#/100mL) (#/100mL) Screening Criteria > 5.0 6-8.5 0.11 2.76 0.20 0.05 26.7 < 200 < 126 Mean 4.03 6.36 0.05 0.02 0.08 0.03 4.68 12.26 5.96 Median 3.25 6.40 0.03 0.02 0.05 0.03 1.85 15.60 5.20 10-HW Maximum 11.00 7.00 0.49 0.02 0.34 0.05 31.20 890.00 151.50 Minimum 0.00 5.60 0.01 0.02 0.03 0.02 0.50 0.50 1.00 25th Perc 1.10 6.20 0.02 0.02 0.05 0.03 0.50 2.00 2.00 n 95 73 16 1 16 16 16 83 63 Mean 4.41 6.41 0.12 NS 0.23 0.03 38.53 13.85 5.50 Median 4.30 6.40 0.14 NS 0.05 0.02 12.95 10.35 5.20 13-HW Maximum 12.08 7.7 0.18 NS 0.82 0.05 149 2120 1445.8 Minimum 0.25 5.3 0.02 NS 0.02 0.01 1 0.5 0.5 25th Perc 1.36 6.2 0.0925 NS 0.035 0.01 7.6 2 1 n 120 121 6 NS 6 6 6 96 125 A denotes geometric mean NS denotes Not Sampled 121
5.0 CADDO LAKE DATA AND TREND ANALYSIS Caddo Lake Watershed Protection Plan Caddo Lake was broken down into sub-areas of the lake (Figure 2) for data analysis. Currently, there are no areas of Caddo Lake impeded by bacteria with no adverse trends based on the data collected (SWQM database supplemented with data collected by Dr. Roy Darville). Levels of E. coli in the southwest region of Caddo Lake have a rising trend which could become an impediment to water quality in Caddo Lake if this trend continues. This region of the lake is influenced by contributions from the Big Cypress Bayou (EC Segment 10) and the Black Cypress Bayou (EC Segment 5). More bacteria data should be collected to determine if the observed increasing levels in the tributaries are adversely affecting the lake. 10000 Segment 14 North Central Fecal Coliform 1000 Concentration (Colonies/100 ml) 100 10 1 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10283 Detections Approximate Location 10283 Non-Detects Grab Sample Criteria Geomean Criteria 122
Segment 14 Northwest Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14236 Detections 14236 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Segment 14 Southwest 1 Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15249 Detections 15249 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria 123
Segment 14 Southwest 2 Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15275 Detections Approximate Location Grab Sample Criteria Geomean Criteria Segment 14 Southwest 3 Fecal Coliform 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14946 Detections Approximate Location Grab Sample Criteria Geomean Criteria Figure 96. Fecal Coliform Concentrations in Caddo Lake. 124
Segment 14 North Central E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 10283 Detections 10283 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Segment 14 Northwest E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14236 Detections 14236 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria 125
Segment 14 Southwest 1 E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15249 Detections 15249 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Segment 14 Southwest 3 E. Coli 10000 1000 Concentration (Colonies/100 ml) 100 10 1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 17867 Detections 17867 Non-Detects Approximate Location Grab Sample Criteria Geomean Criteria Figure 97. E. coli Concentrations in Caddo Lake. 126
5.1 TOTAL PHOSPHORUS Caddo Lake Watershed Protection Plan Area SW2 exceeded the TP screening criteria for three out of five records between June 1997 and April 1999. Sub-area NW, located inside Caddo Lake downstream of EC Segment 11 (Kitchen Creek) had 14.3% of the total records exceeding the screening criteria and has a rising trend for TP concentration (Appendix B Segment 14). SW1, the first monitoring stations downstream of EC Segment 10 (Big Cypress Bayou), has only 16.1% of the records exceeding the screening criteria for TP but also has a rising trend. TP does not pose an impediment for the sub-area NC, located in the middle section of Caddo Lake though the trend shows a rise and should continue to be monitored. 127
128
Figure 98. Total Phosphorus Concentrations in Caddo Lake 129
5.2 AMMONIA Caddo Lake Watershed Protection Plan Ammonia data collected in Caddo Lake indicate low concentrations with occasional spikes. The data do not indicate any adverse trends. Ammonia typically breaks down rapidly and is oxidized into NOx, which is readily available for plant uptake. 130
131
5.3 NITRITE-NITRATE (NOx) Figure 99. Caddo Lake Ammonia Observations. Caddo Lake has been monitored fairly extensively for NOx at the north central segment as well as the first and third segments in the southwest portion of the lake (NC, SW1, and SW3) with little to no sampling in the remainder of lake. None of these records exceeded the reservoir screening criteria. Because limited data were collected and much of the data are reported at the detection limit, trends could not be determined. Additional data should be collected in more locations within the lake near the river confluences to provide data for trend analyses and to characterize lake interactions. 132
Segment 14 North Central Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1980 1985 1990 1995 2000 2005 2010 10283 Detections 10283 Non-Detects Approximate Location Screening Level Segment 14 Northwest Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14236 Detections 14236 Non-Detects Approximate Location Screening Level 133
Segment 14 Southwest 1 Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15249 Detections 15249 Non-Detects Approximate Location Screening Level Segment 14 Southwest 2 Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15275 Detections 15275 Non-Detects Approximate Location Screening Level 134
Segment 14 Southwest 3 Nitrate plus Nitrite 3.0 2.5 Concentration (mg/l as N) 2.0 1.5 1.0 0.5 0.0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14946 Detections 14946 Non-Detects Approximate Location 17867 Detections 17867 Non-Detects Screening Level Figure 100. Total Nitrite-Nitrate Nitrogen (NOx) Concentrations in Caddo Lake. 5.4 OTHER PARAMETERS OF INTEREST The chlorophyll-a concentration exceeded the screening criteria for two values of the four samples collected in SW2, for 4 values out of 31 samples in SW1, and 4 out of 23 samples in SW3. Chlorophyll-a exceeded the screening limit in 14.3% of readings in NW, and 13.2% in NC with a rising trend (Figure 101). Orthophosphate concentrations were plotted for the sub-areas within Caddo Lake (Figure 102). The majority of the observations were reported at the detection limit thus a trend cannot be determined. In addition, some data reported at the detection limit is higher than the screening criteria in the north central section of the lake. 135
Segment 14 North Central Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1970 1975 1980 1985 1990 1995 2000 2005 2010 10283 Detections 10283 Non-Detects Approximate Location Screening Level Segment 14 Northwest Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14236 Detections 14236 Non-Detects Approximate Location Screening Level 136
Segment 14 Southwest 1 Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 15249 Detections 15249 Non-Detects Approximate Location Screening Level Segment 14 Southwest 2 Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 15275 Detections 15275 Non-Detects Approximate Location Screening Level 137
Segment 14 Southwest 3 Chlorophyll-a 200 150 Concentration (ug/l) 100 50 0 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 14946 Detections 14946 Non-Detects Approximate Location 17867 Detections 17867 Non-Detects Screening Level Figure 101. Chlorophyll-a Concentrations in Caddo Lake 138
139
Figure 102. Orthophosphate Concentrations in Caddo Lake. 140
5.5 TREND ANALYSIS - PH Caddo Lake Watershed Protection Plan The mid-lake stations, in sub-area NC, have the highest ph values on average (Table 6), and fall below the bounds of the screening limit 6.25% of the time and above the bounds of the screening limit 3.3% of the time. The mean ph value for sub-area SW3 is the next highest (Table 6) and does not appear to have any adverse trends (Figure 103) with the values falling below the screening limit only 5.9% of the time in the period of record. The NW sub-area of Caddo Lake does not meet the screening criteria 12.8% of the time and has a mean value of 6.32. Area SW1 fell below the screening limit 16.9% of the time but has an upward trend. The records for SW2 indicate concern for ph since the average value was 5.81 for the 13 records with 53.8% falling below the screening limit. 141
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 NC - ph 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 1.000 0.000 10/28/1972 4/20/1978 10/11/1983 4/2/1989 9/23/1994 3/15/2000 9/5/2005 Date 142
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 NW - ph 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 1.000 0.000 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006 7/6/2009 Date 143
144
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 SW1 - ph 9.000 8.000 7.000 6.000 5.000 4.000 3.000 2.000 ph Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 1.000 0.000 5/25/1979 11/14/1984 5/7/1990 10/28/1995 4/19/2001 10/10/2006 Date 145
5.6 TREND ANALYSIS - DO Figure 103. ph Values in Caddo Lake Depressed DO levels occur in sub-areas NW, SW1, and SW2 with mean values (Table 6) below 5.0 mg/l (screening criteria). SW3 has an average of 5.41 mg/l DO but falls below the screening criteria in 41.2% of the records, thus creating a secondary issue. The only area with DO not illustrating a depressed state is NC, located in the middle of Caddo Lake further from the influence of the contributing drainage areas and where more re-aeration occurs from the surface of the lake. 146
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 NC - DO 16.000 14.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 12.000 10.000 8.000 6.000 4.000 2.000 0.000 10/28/1972 4/20/1978 10/11/1983 4/2/1989 9/23/1994 3/15/2000 9/5/2005 Dissolved Oxygen (mg/l) Date 147
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 NW - DO 16.000 14.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 12.000 10.000 8.000 6.000 4.000 2.000 0.000 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006 7/6/2009 Dissolved Oxygen (mg/l) Date 148
149
Linear Regression with 95% Confidence Interval for the Mean Response EC Segment 14 SW1 - DO 16.000 14.000 DO Linear Regression Confidence Interval for Mean Response Confidence Interval for Mean Response 12.000 10.000 8.000 6.000 4.000 2.000 0.000 10/6/1980 3/29/1986 9/19/1991 3/11/1997 9/1/2002 2/22/2008 Dissolved Oxygen (mg/l) Date 150
Figure 104. DO Concentrations in Caddo Lake. 151
EC Segment 14-NC 14-NW 14-SC 14-SW1 14-SW2 14-SW3 Table 6. Summary Statistics for Caddo Lake by Sub-Area NH 3 NOx Ortho Chloro FC A E. coli A Parameter DO (mg/l) ph (mg/l) (mg/l) TP (mg/l) (mg/l) (u g/l) (#/100mL) (#/100mL) Screening Criteria > 5.0 6-8.5 0.11 0.32 0.20 0.05 26.7 < 200 < 126 Mean 7.94 6.90 0.07 0.04 0.08 0.03 12.98 29.52 7.18 Median 8.01 6.90 0.05 0.03 0.05 0.02 7.00 5.00 2.00 Maximum 15.50 9.38 0.72 0.15 1.11 1.03 150.00 900.00 137.40 Minimum 0.10 5.40 0.01 0.01 0.01 0.00 0.50 0.00 0.00 25th Perc 6.90 6.40 0.03 0.02 0.03 0.01 2.00 1.70 0.50 n 394 385 116 57 114 109 105 178 153 Mean 4.66 6.32 0.06 0.05 0.13 0.03 8.86 39.29 16.14 Median 4.60 6.30 0.04 0.05 0.09 0.03 3.84 12.00 5.10 Maximum 12.90 7.40 0.16 0.09 0.45 0.15 40.00 390.00 143.90 Minimum 0.10 5.50 0.03 0.01 0.01 0.01 0.50 0.00 0.50 25th Perc 1.20 6.10 0.03 0.03 0.06 0.02 0.50 3.00 2.00 n 127 127 14 2 14 13 14 57 54 Mean 7.50 6.00 NS NS NS NS NS NS NS Median 7.50 6.00 NS NS NS NS NS NS NS Maximum 7.50 6.00 NS NS NS NS NS NS NS Minimum 7.50 6.00 NS NS NS NS NS NS NS 25th Perc 7.50 6.00 NS NS NS NS NS NS NS n 1 1 NS NS NS NS NS NS NS Mean 4.99 6.31 0.09 0.03 0.09 0.01 11.61 44.26 31.93 Median 4.78 6.30 0.07 0.02 0.08 0.01 6.00 5.60 11.45 Maximum 14.00 8.00 0.33 0.11 0.34 0.03 37.00 580.00 1300.00 Minimum 0.14 5.00 0.01 0.02 0.01 0.01 1.00 0.00 0.00 25th Perc 1.70 6.10 0.02 0.02 0.03 0.01 3.25 2.00 3.78 n 165 141 31 31 31 12 12 73 148 Mean 4.89 5.81 0.15 0.05 0.21 0.02 27.50 380.00 NS Median 5.30 5.90 0.15 0.05 0.14 0.02 23.50 380.00 NS Maximum 8.50 6.60 0.23 0.05 0.52 0.03 62.00 380.00 NS Minimum 0.16 4.90 0.07 0.05 0.07 0.01 1.00 380.00 NS 25th Perc 2.69 5.30 0.12 0.05 0.10 0.01 9.25 380.00 NS n 12 13 5 1 5 4 4 1 NS Mean 5.41 6.47 0.03 0.05 0.12 0.03 21.64 17.00 9.67 Median 5.85 6.35 0.03 0.05 0.06 0.03 10.40 10.00 2.50 Maximum 10.20 8.00 0.10 0.05 1.35 0.05 203.00 33.00 53.00 Minimum 0.20 5.60 0.01 0.01 0.03 0.02 0.50 8.00 0.50 25th Perc 2.53 6.20 0.03 0.05 0.03 0.03 5.00 9.00 0.50 n 34 34 23 13 23 23 23 3 18 152
6.0 PRIORITIZING POLLUTANT SOURCE PARAMETERS BY LOCATION Preliminary pollutant source locations were identified by characterizing the watershed with available data, noting point sources and their contributions, and evaluating the land use for potential non-point sources. Further, flow vs. concentration plots were created where applicable using U.S. Geological Survey (USGS) flow gauges to determine if in fact increased concentrations are directly related to increased flow (due to runoff) indicating non-point source contributions. In addition, precipitation vs. concentration using National Climatic Data Center (NCDC) precipitation data was plotted for the segments where flow data were not available. 6.1 LANDUSE CHARACTERIZATION The land use for the Cypress Creek Basin was characterized by utilizing digitized aerial photography (obtained from the Texas Natural Resources Information System, 1-m resolution) and the classification scheme developed by Castilaw Environmental and then comparing the aerial imagery with the National Land Cover Dataset (NLCD) 2001 in ArcGIS 9.2. Roughly two-thirds of the entire Cypress Creek Basin is classified as forests. The next largest, roughly 28%, land use classification is agricultural uses (combined cropland and pastures). The vast majority of the agricultural land is utilized as pastures rather than cropland. The remaining land is classified as urban (residential and commercial development), water and wetlands, or undeveloped rangeland. In general, the landscape is more agricultural in the southwest and becomes more forested towards the northeast. The land use characterization is presented in Figure 105. The NLCD 2001 was downloaded in TIFF format from the U. S. Department of Agriculture (USDA) Geospatial Data Gateway website (http://datagateway.nrcs.usda.gov/gatewayhome.html). It was converted from a 30-m pixel TIFF to ESRI GRID format using the Spatial Analyst extension of ArcGIS 9.2 in order to perform a reclassification and subsequently convert to a shapefile. Three of the four NLCD categories representing developed land were reclassified to better match the categories established by Castilaw Environmental: open space, low intensity, and medium intensity. These three were reclassified to Urban/built-up. Those NLCD categories that did not have a direct match with a Castilaw category became new categories. A breakdown of NLCD 2001 categories and the Castilaw/Espey categories (Table 7) illustrates where direct matches, new categories, and reclassifications were performed. EC used the Castilaw/Espey categories for this project. 153
Table 7. Land Use Comparison and Conversion for the Cypress Creek Basin NLCD Castilaw/Espey Open Water Open Water Developed, Open Space *1a reclassified > Urban or Built-Up Developed, Low Intensity reclassified > Urban or Built-Up Developed, Medium Intensity reclassified > Urban or Built-Up Developed, High Intensity *1b Commercial/Industrial Baren Land (rock, sand, clay) Barren Land *2 Deciduous Forest Deciduous Forest *3 Evergreen Forest Evergreen Forest Land Mixed Forest Mixed Forest Land Shrub/Scrub Shrub/Scrub *4 Grassland/Herbaceous Grassland/Herbaceous *5 Pasture/Hay *6 Pasture Cultivated Crops Cropland Woody Wetlands *7 Forested Wetlands Emergent Herbaceous Wetlands Emergent Herbaceous Wetlands *8 *1a. Developed-Open Space is mostly vegetation in the form of lawn grasses commonly found in large-lot singlefamily housing developments, parks, golf courses and other recreational areas, and land reserved for erosion control or aesthetic purposes and may be mixed with some constructed material. This description suggests it should not be mixed with any forest, pasture, or cropland. *1b. Developed-High Intensity includes apartment complexes and row houses in addition to commercial and industrial. Apartment complexes and row houses are very rare in this rural area of the state where single-family and ranch/farm houses are prevalent. Thus, this category mainly represents commercial/industrial land uses. *2. Barren land includes strip mines and gravel pits along with naturally occurring barren areas of bedrock or other earthen material. This NLCD category did not have a direct match with a Castilaw category and was added as a new category. *3. Deciduous forest differs from evergreen or mixed forests and was added as a category. *4. Shrub/Scrub is an NLCD category that did not have a direct match with a Castilaw category. Rather than combining with a forest type, it was added as a category. *5. Grassland is an NLCD category that did not have a direct match with a Castilaw category and was added as a new category. These areas can be used for grazing, yet unlike pasture are not subject to intensive management. *6. Pasture/Hay consolidates two categories. Pasture is mostly subject to grazing, and therefore may contain fecal material that may affect surface water quality. Production of seed or hay crops is also possible and presents a separate potential impact to surface water from pesticides and fertilizers. *7. Woody Wetlands appear in many areas, but in the 2004 aerial imagery just looks like regular forested land. *8. Emergent Herbaceous Wetland was added as a new category because the of the potential need to identify such wetlands for habitat purposes. 154
Figure 105. Land Use Characterization for the Cypress Creek Watershed. 155