Hydrologic Conditions for the month of August 2003

Transcription

1 Hydrologic Conditions for the month of August 2003 Prepared by the Hydrologic Data Section Operations Department

2 TABLE OF CONTENTS Introduction...1 Executive Summary Provisional...2 Executive Summary...3 Regional Overview...4 Rainfall Surface Water Lakes Streams Springs Ground Water Surficial Aquifer Intermediate and Floridan Aquifers Public Supply Wellfields Aquifer Resource Water Demand Public Supply Surface Water Reservoirs Reservoirs Appendices Rainfall Percentiles by Interval & Region Lake Monitoring Stations Stream Monitoring Stations Description of Stream Monitoring Stations Springs Monitoring Stations Description of Springs Monitoring Stations Surficial Aquifer Monitoring Stations Groundwater Monitoring Stations Wellfield Groundwater Monitoring Stations Aquifer Resource Monitoring Stations

3 ACKNOWLEDGMENTS The Hydrologic Conditions Report is a monthly effort of the Operation's Department Hydrologic Data Section. Acknowledgment is made to the following staff for their significant contributions, hard work and dedication to the timely production of this report: Data Collection: SCADA System: QA/QC and Reporting: Administrative Support/ Document Preparation: Terry Burrell, Mark Condron, Dave Dunnett, Don Everson, George Prine, Steve Saxon, Terrie Stanley and Jamie Williams. Mike Bartlett. Margit Crowell, JoAnn Gilroy, Pam Green, Eileen Ratliff, Ken Romie and Mary Ann Wolf. Della Haberle, Wiladean Kelso

4 INTRODUCTION The Hydrologic Conditions Report is generated monthly by the Hydrologic Data Section, Operations Department, of the Southwest Florida Water Management District. This report provides an end-of-month analytical summary of regional and temporal variations in the hydrologic conditions across the District s 16-county area for planning and regulatory purposes. In addition, it provides an excellent historical record for long-term local and regional hydrologic analysis. The Hydrologic Data Section is responsible for the implementation and maintenance of a network of observation and monitoring stations used to track changes in various hydrologic parameters over time. Data collected are used by the regulatory, technical, and analytical sections of the District. Data recently collected and maintained by the section include: station and basin rainfall totals, stream and spring discharge measurements, and surface and ground water levels. Frequency of data collection ranges from hourly to monthly readings. All data collected are processed and analyzed, then uploaded into the Water Management Data Base for general access by the District. The Water Management Data Base is also periodically augmented from the United States Geological Survey s hydrologic data network. The data presented in this report are monthly rainfall totals, streamflow, springflow, surface and ground water levels, reservoir levels and the Aquifer Resource Index. Associated maps of station locations are at the end of the report in the Appendices. Also reported herein are levels of public supply surface water reservoirs supplemented by various regional utilities. Any questions about the significance, accuracy, or interpretation of these data should be referred to Granville Kinsman, Manager of the Hydrologic Data Section at (352) or (800) , extension The data evaluation, analyses and interpretation contained within this report have been prepared or approved by a certified Professional Geologist in accordance with Chapter 492, Florida Statutes. 09/18/03 Registration #PG Americans with Disabilities Act (ADA) The Southwest Florida Water Management District (District) does not discriminate upon the basis of any individual s disability status. This non-discrimination policy involves every aspect of the District s functions, including one s access to, participation, employment, or treatment in its programs or activities. Anyone requiring reasonable accommodations as provided by the Americans with Disabilities Act should contact Renetta Thompson at (352) or (FLORIDA), extension 4318 or SUNCOM ; TDD ONLY (FLORIDA); FAX (352) /SUNCOM

5 EXECUTIVE SUMMARY Provisional Hydrologic Conditions as of September 15, 2003 Provisional average rainfall totals for September 1, 2003 through September 15, 2003 are as follows: the northern region received an average of 2.40 inches of rain, equivalent to 37 percent of the monthly mean of 6.44 inches. The central region received 2.82 inches of rainfall, equivalent to 40 percent of the monthly mean of 7.01 inches. The southern region recorded an average of 3.84 inches of rain, equivalent to 51 percent of the monthly mean of 7.48 inches. Provisional lake data indicate that water levels have increased in two of the four regions of the District from September 1, 2003 to September 15, Average lake levels in the northern region increased 0.30 foot and are 1.48 feet above adopted Minimum Low Management (MLM) levels. Lake levels in the Tampa Bay region decreased an average of 0.08 foot and are 1.67 feet above adopted MLM levels. Lake levels in the Polk Uplands region decreased 0.20 foot and are 1.76 feet above adopted MLM levels. Lake levels in the Lake Wales Ridge region posted an average increase of 0.81 foot, and are 0.55 foot above their adopted MLM levels. Provisional data show streamflow has increased in the northern and southern regions, but decreased in the central region during the first 15 days of September. Provisional groundwater data indicate that average water levels have increased in the northern and southern regions, but decreased in the central region of the District from September 1, 2003 to September 15, Water levels in the northern and southern regions increased 0.20 and 0.01 foot, respectively, while levels in the central region decreased 0.31 foot.

6 EXECUTIVE SUMMARY Hydrologic Conditions for August 2003 In August, the District-wide rainfall average was 9.69 inches, which was 1.66 inches above the monthly normal of 8.03 inches. This rainfall average was equivalent to the 82 nd percentile of historical August readings and is classified as "wetter than normal." The northern region received an average of 8.55 inches of rainfall, which was 0.60 inch above the monthly normal of 7.95 inches. This rainfall average is equivalent to the 60 th percentile of historical August readings and is classified as "normal." The central region received an average of 9.75 inches of rainfall, which was 1.36 inches above the monthly normal of 8.39 inches. This rainfall average is equivalent to the 76 th percentile of historical August readings and is classified as "wetter than normal." The southern region received an average of inches of rainfall, which was 2.47 inches above the monthly normal of 7.97 inches. This rainfall average was equivalent to the 89 th percentile of historical August readings and is classified as "wetter than normal." During the 12-month period from September 1, 2002 through August 31, 2003, all three regions reported above-normal rainfall. The northern region received an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 93 rd percentile of historical 12-month cumulative readings and is classified as "very wet." The central region received an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 97 th percentile of historical 12-month cumulative readings and is classified as "very wet." The southern region received an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 91 st percentile of historical 12-month cumulative readings and is classified as "very wet." District-wide, the 12- month rainfall average of inches of rainfall was inches above the yearly normal of inches. This rainfall average is equivalent to the 94 th percentile of historical 12-month cumulative readings and is classified as "very wet." Average lake levels in the northern region of the District increased 0.72 foot, and are 1.18 feet above adopted Minimum Low Management (MLM) levels. Lake levels in the Tampa Bay region increased an average of 0.37 foot, and ended the month at 1.75 feet above adopted MLM levels. Lake levels in the Polk Uplands region increased 0.15 foot, and ended the month 1.96 feet above their adopted MLM levels. Lake levels in the Lake Wales Ridge region increased 0.80 foot, but ended the month at 0.26 feet below adopted MLM levels. Total streamflow increased in all three regions of the District in August. Streamflow measured in the northern region totaled cfs, while streamflow in the central and southern regions totaled and cfs, respectively. Ground-water levels in the Floridan aquifer increased in all three regions of the District in August. Water levels in the northern and central regions increased 0.90 and 0.87 foot, respectively, while levels in the southern region increased 2.06 feet. Water levels measured in the Floridan aquifer at representative wellfields increased an average of 1.99 feet.

7 Northern Region REGIONAL OVERVIEW OF HYDROLOGIC CONDITIONS August 2003 In August, the northern region received an average of 8.55 inches of rainfall, which was 0.60 inch above the monthly normal of 7.95 inches. This rainfall average is equivalent to the 60 th percentile of historical August readings and is classified as "normal." Lake levels increased in the northern region, and ended the month an average of 1.18 feet above the Minimum Low Management (MLM) levels. Total streamflow increased during August. Regional comparison of total springflow to last month could not be determined because of missing station data. The mean water level increased in the surficial aquifer wells by 0.30 foot, while the levels in intermediate and Floridan aquifer wells increased 0.90 foot. Central Region In August, the central region received an average of 9.75 inches of rainfall, which was 1.36 inches above the monthly normal of 8.39 inches. This rainfall average is equivalent to the 76 th percentile of historical August readings and is classified as "wetter than normal." Water levels increased in the Tampa Bay region s lakes, and ended the month an average of 1.75 feet above MLM levels. Lake levels increased in the Polk Uplands region, and ended the month an average of 1.96 feet above MLM levels. Total streamflow increased during August. Regional comparison of total springflow to last month could not be determined because of missing station data. The mean water level in the surficial aquifer wells increased 0.91 foot, while average water levels increased 0.87 foot in the intermediate and Floridan aquifer wells. Southern Region In August, the southern region received an average of inches of rainfall, which was 2.47 inches above the monthly normal of 7.97 inches. This rainfall average was equivalent to the 89 th percentile of historical August readings and is classified as "wetter than normal." Lake levels increased in the Lake Wales Ridge region, but ended the month an average of 0.26 foot below MLM levels. Total streamflow increased during August. Regional comparison of total springflow to last month could not be determined because of missing station data. The mean water level increased in the surficial aquifer wells by 0.90 foot, while levels in the intermediate and Floridan aquifer wells increased 2.06 feet.

8 RAINFALL Determination of Rainfall Characterization Ranges Historical rainfall amounts (1915 to most recent complete calendar year) are summarized annually for regions within the Southwest Florida Water Management District. These totals are reported in spreadsheets available from the District's web site ( by region, county, USGS drainage basin, CWM basin, and political basin. Rainfall characterizations, with the exception of annual total, were calculated from the historical regional rainfall summary report. Wet season total is the sum of the rainfall for the months from August through September. Dry season total is the sum of the rainfall for the months from October through May. The annual total characterization was calculated from a dataset of moving 12-month rainfall sum for the same period (1915 through the most recent completed year). The moving 12-month rainfall sum was used for annual statistics because it provided a much larger dataset, and therefore a better estimate of the true percentiles. The historical 12-month cumulative average is updated monthly. Percentiles were calculated from the historical record by region, and by specific interval. Characterization ranges were established for each region, and for the whole District, with breaks at the 10 th (P10), the 25 th (P25), the 75 th (P75) and the 90 th (P90) percentiles. The rainfall in inches for each percentile break, by rainfall interval and by region, is summarized in the Appendix. The characterization ranges are summarized in the Appendix. In August, the District-wide rainfall average was 9.69 inches, which was 1.66 inches above the monthly normal of 8.03 inches. This rainfall average was equivalent to the 82 nd percentile of historical August readings and is classified as "wetter than normal." The northern region received an average of 8.55 inches of rainfall, which was 0.60 inch above the monthly normal of 7.95 inches. This rainfall average is equivalent to the 60 th percentile of historical August readings and is classified as "normal." The central region received an average of 9.75 inches of rainfall, which was 1.36 inches above the monthly normal of 8.39 inches. This rainfall average is equivalent to the 76 th percentile of historical August readings and is classified as "wetter than normal." The southern region received an average of inches of rainfall, which was 2.47 inches above the monthly normal of 7.97 inches. This rainfall average was equivalent to the 89 th percentile of historical August readings and is classified as "wetter than normal." During the 12-month period from September 1, 2002 through August 31, 2003, all three regions reported above-normal rainfall. The northern region received an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 93 rd percentile of historical 12-month cumulative readings and is classified as "very wet." The central region received an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 97 th percentile of historical 12- month cumulative readings and is classified as "very wet." The southern region received

9 an average of inches of rainfall, which was inches above the yearly normal of inches. This rainfall average is equivalent to the 91 st percentile of historical 12- month cumulative readings and is classified as "very wet." District-wide, the 12-month rainfall average of inches of rainfall was inches above the yearly normal of inches. This rainfall average is equivalent to the 94 th percentile of historical 12- month cumulative readings and is classified as "very wet." Tampa Monthly Climate Summary for August 2003 According to the National Weather Service (NWS), the monthly average temperature in the Tampa Bay area was 81.9 degrees, which was 0.8 degree below normal. The lowest temperature recorded in the Tampa Bay area was 72 degrees, while the highest temperature recorded was 93 degrees. Tropical Weather Summary for August 2003 According to the NWS, four tropical systems (Tropical Storm Erika, Tropical Depression Nine, Hurricane Fabian and Tropical Storm Grace) developed in the Atlantic Basin during August. For a complete tropical weather monthly summary, please visit the Tropical Prediction Center's website at: Scroll down to "Current Season Summaries and Reports." Temperature and Precipitation Outlook The Climate Prediction Center (CPC) is forecasting above normal temperature and climatology (equal chances for above, normal or above normal conditions) for precipitation during September Additionally, the CPC is forecasting climatology for temperature and precipitation for October 2003 through December For more information log onto the CPC's website at:

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13 SWFWMD Rainfall Distribution August 2003 Very dry Drier than normal Normal Wetter than normal Very wet

14 SWFWMD Rainfall Distribution September 2002 through August 2003 Very dry Drier than normal Normal Wetter than normal Very wet

15 SURFACE WATER Lakes Across the District, 76 lakes have been selected as excellent indicators of current surface water conditions (see index map in Appendix). Water levels of these lakes are read monthly. In general, these lakes are concentrated in four regions, the northern region of Citrus, Hernando, and Sumter Counties, the Tampa Bay region of Hillsborough and Pasco Counties, the Polk Uplands region of northern Polk County, and the Lake Wales Ridge region of Polk and Highlands Counties. In this report, current monthly lake levels are tabulated and compared with previous records as well as District-established management levels, except for Big Fish Lake in the northern region. In addition, lake-level data representative of the four regions are presented in hydrographs, as a general indicator of surface-water conditions in that region. To date, the District's Governing Board (the Board) has adopted management levels for 397 lakes within District boundaries. These management levels are established for managing the natural water-level fluctuations necessary for maintaining healthy lake environments. In this report, the following three management levels are used to indicate normal lake levels: the Minimum Extreme Low level, the Minimum Low level, and the Minimum Flood level. These levels are derived from various sources, including technical publications, topographic maps, Water Resource Data Reports of the United States Geological Survey (USGS), and other studies. Field investigations are also used to determine past surface levels from water marks, wetland vegetation, dry land vegetation, and to establish the elevation of septic tanks, docks, sea walls, roads and floor slabs. The Minimum Extreme Low Management (MELM) level is a drought-year low. The adopted Minimum Low Management (MLM) level is the annual normal low level for the lake. It can be employed to regulate lake augmentation and withdrawal, as well as a guide to operate control structures. The Minimum Flood (MF) level is defined as the highest elevation in feet to which a lake will be allowed to fluctuate without interference except as approved by the Board for the purpose of conserving the waters in the state. This level approximates the annual normal high-water elevation of the lakes. During a normal year, each of the indicator lakes should reach both the designated normal high (MF) and the normal low (MLM) levels. In addition, it is generally beneficial for lakes to reach the adopted drought year low (MELM) level every four to six years for a short period of time for the biological health of the lake. In this report, hydrographs of representative lakes compare current and recent water levels against normal ranges defined by the adopted MF and MLM levels. Of the 76 lakes presented in this report, 17 have water-control structures. These structures are used for water conservation and do not generally influence the water levels with regard to meteorologically wet or dry conditions. During periods of extreme high water, the structures may be operated to minimize flooding.

16 In August, water levels rose in 58 of the 76 lakes monitored for this report. Regionally, average lake levels in the northern region increased 0.72 foot, while lake levels in the Tampa Bay increased 0.37 foot. Average lake levels in the Polk Uplands region increased 0.15 foot, while levels increased 0.80 foot in the Lake Wales Ridge region. In lakes District-wide, levels increased 0.43 foot on average compared to last month. In August, average water levels were higher in 74 of the 76 lakes compared to August Water level readings from one lake, Bay Lake in the Tampa Bay region, were missing last year so a comparison could not be made. In the northern region, average lake levels were 3.99 feet higher than last year s levels. In the Tampa Bay region, average lake levels were 4.03 feet higher than last year s levels, while the levels in the Polk Uplands region were 2.99 feet higher than last year. Lake levels in the Lake Wales Ridge region were 2.73 feet higher than last year s levels. District-wide, average lake levels were 3.60 feet higher than last year's levels. Water levels in 63 of the 75 lakes with adopted levels were above Minimum Low Management (MLM) levels. Average lake levels in the northern region were 1.18 feet above MLM levels. Lake levels in the Tampa Bay and Polk Uplands regions averaged 1.75 and 1.96 feet above respective MLM levels, while levels in the Lake Wales Ridge region averaged 0.26 foot below MLM levels. District-wide, average lake levels were 1.46 feet above MLM levels.

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23 Streams Streamflow data are recorded daily as water elevations at 12 gauging stations in three regions of the District (see index map in the Appendix). Using rating curves developed by the USGS, the water elevations are used to calculate discharge in units of cubic feet per second (cfs). For this report, the reported streamflow values are the means of the daily discharge volumes for the current month. The periodof-record high and low values correspond to monthly means and not to peak events. Percentile values are calculated from the monthly means for the period of record, for each station. The percentile is the monthly mean statistically ranked on a scale of zero to 100 that indicates the percent of the period-of-record monthly means that are at or above the present monthly mean. The current year s data are provisional, and are subject to revision. Revised data are used for all calculations, as they become available. Hydrographs are produced for each of the stream stations. Current monthly means for each station are compared to respective 25 th and 75 th percentiles of the period-of-record monthly means. In August, all 12 stations monitored reported increasing streamflow. Total streamflow increased in the northern region by cfs (715.7 mgd), while streamflow increased in the central and southern regions by cfs (426.9 mgd) and cfs ( mgd), respectively, during August. All 12 monitoring stations recorded higher streamflow in August 2003 than in August Streamflow in the northern and central regions was cfs ( mgd) and cfs (694.7 mgd) higher than respective August 2002 rates. Streamflow in the southern region was cfs ( mgd) higher than the August 2002 rate. Compared to historical August discharge values, streamflow measured at the Withlacoochee River Holder and Trilby stations in the northern region were in the 97 th and 98 th percentiles, respectively. Streamflow measured at the Anclote, Hillsborough and Pithlachascotee River stations in the central region averaged in the 91 st, 90 th, and 95 th percentiles of respective historical August readings. Streamflow measured at the Alafia River, Josephine Creek and Little Manatee River stations in the southern region averaged in the 88 th, 92 nd, and 92 nd percentiles of respective historical August readings. Additionally, streamflow measured at the Manatee, Myakka and Peace at Arcadia and Bartow stations in the southern region averaged in the 100 th, 94 th, 93 rd, and 81 st percentiles of respective historical August readings.

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28 Springs Springflow data for Rainbow, Silver and Sulphur Springs are recorded as daily water levels. Using rating curves developed by the USGS, these levels are converted into estimated discharge in units of cubic feet per second (cfs). Crystal and Weeki Wachee Springs discharge (cfs) is provided as an instantaneous reading calculated by the USGS. Buckhorn and Lithia Springs discharge is obtained from Tampa Bay Water biweekly and weekly, respectively. Period-ofrecord high and low values correspond to monthly theoretical means and not to peak events. Values are reported as percentiles calculated from an analysis of historical monthly means recorded during a given month. The percentile is the monthly theoretical mean statistically ranked on a scale of zero to 100 that indicates the percent of period-of-record values that are above, equal to or above the median (50 th percentile) for the current month. The values reported are provisional, and are subject to revision at the end of the water year. Revised USGS springflow data are loaded into the District s WMDB when they become available. Hydrographs are produced for the seven-springflow stations, and current values are compared to respective 25 th and 75 th percentiles that are calculated from historical data. The 25 th and 75 th percentiles are calculated using the SAS TM software system for data analysis using period-of-record monthly theoretical means for each springflow station analyzed. In August, four stations had data available for this report and all four stations reported increasing springflow. Readings could not be obtained for the Crystal Springs in the central region and Lithia Springs in the southern region due to flooding conditions. Springflow for the Silver Springs station in the northern region will not be available until the USGS develops a new rating curve used in the calculation of discharge for the spring. Consequently, total springflow values for all three regions and the District-wide total value could not be calculated. Compared to historical period-of-record values, total springflow measured in the Rainbow and Weeki Wachee Springs in the northern region was in the 80 th and 100 th percentiles of respective historical readings. Springflow measured in the Sulphur Springs in the central region was in the 51 st percentile of historical readings. Springflow measured in the Buckhorn Springs in the southern region was in the 85 th percentile of historical readings.

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32 GROUND WATER Thirteen surficial aquifer (shallow, non-artesian) and 54 intermediate and Floridan aquifer (deep) monitor wells located in three regions of the District are measured weekly for this report. The potentiometric levels of representative deep wells are used to produce the potentiometric surface maps presented in this report. To indicate the ground-water status District-wide, water levels measured in 54 deep wells are analyzed (see index maps in the Appendix). The monthly water-level readings are compared to the corresponding historical record for each well using period-of-record data. In this report, data from 16 deep wells are shown in hydrographs to compare current water levels to the low normal (16 th percentile of historical monthly readings) and the high normal (84 th percentile of historical monthly readings). The high normal and low normal thresholds define the upper and lower boundaries of the normal range for the wells. During periods of declared water shortages, water-level measurements may be measured more frequently in the affected areas. Surficial Aquifer During August, 11 of the 13 surficial aquifer wells recorded water level increases. Regionally, average surficial water levels in the northern region increased 0.30 foot. In the central and southern regions, average water levels increased 0.91 and 0.90 foot, respectively. District-wide, the mean water level in surficial wells increased 0.81 foot. Average water levels in 11 of the 13 surficial aquifer wells were higher than August 2002 levels. Average surficial water levels in the northern and central regions were 3.09 and 1.53 feet, respectively, higher than last year s levels. Water levels in the southern region were 0.01 foot higher than last year s levels. District-wide, average water levels in surficial wells were 0.95 foot higher than August 2002 levels. At the end of August, water levels were within the normal range in all 13 surficial wells. Regionally, average surficial aquifer water levels in the northern region were 4.48 feet higher than the bottom of the normal range, while levels in the central and southern regions were 4.15 and 2.59 feet above the bottom of the normal range. District-wide, the average water level in surficial wells was 3.36 feet above the bottom of the normal range.

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34 Intermediate and Floridan Aquifers During August, 53 of the 54 intermediate and Floridan aquifer wells monitored for this report recorded water level increases. Regionally, average water levels increased in the northern and central regions by 0.90 and 0.87 foot, respectively. Average water levels in the southern region increased 2.06 feet. District-wide, the mean water level in intermediate and Floridan aquifer wells increased 1.49 feet. In August, water levels in all 54 intermediate and Floridan aquifer wells were higher than those measured in August Regionally, mean water levels were 4.76 and 2.00 feet higher in the northern and central regions, respectively, while levels were 4.57 feet higher in the southern region. District-wide, average water levels in the intermediate and Floridan aquifer wells were 4.15 feet higher than last year. During August, 53 of the 54 intermediate and Floridan aquifer wells had levels above low normal compared to historical monthly levels. Regionally, the average water level in the northern region was 6.61 feet above the bottom of the normal range, while the average levels in the central and southern regions were 4.38 and 8.88 feet above low normal. District-wide, the average water level in the intermediate and Floridan aquifer wells was 7.38 feet above low normal.

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44 Public Supply Wellfields Water levels are measured in 21 monitor wells (nine surficial, 12 intermediate and Floridan aquifer wells) located at nine public supply wellfields in the District. Thirteen of the 21 monitor wells have water levels measured monthly, two biweekly, and six weekly. Monthly data are tabulated to compare recent water levels to historical means. During August, average water levels increased in 11 of the 12 intermediate and Floridan wells and seven of the nine surficial wells. Average water levels measured in the intermediate and Floridan wells increased 1.99 feet, while levels measured in surficial wells increased 1.02 foot. In August, average water levels in all 12 intermediate and Floridan wells and all nine surficial wells were above those measured in August Water levels measured in the intermediate and Floridan wells averaged 6.81 feet above last year s levels, while surficial water levels averaged 8.02 feet above August 2002 levels. At the end of August, average water levels in all 12 intermediate and Floridan wells and all nine surficial wells were above low normal compared to historical monthly levels. Water levels measured in the intermediate and Floridan wells averaged feet above low normal, while levels in the surficial wells averaged 8.83 feet above low normal.

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46 Aquifer Resource Index The Aquifer Resource Index (ARI) was created to determine the relation of groundwater levels to low-normal values, as well as to indicate the overall health of the ground-water resources within the three regions of the District. Each region is characterized by the physical and lithological components of the underlying rock strata that make up the aquifer systems. In the northern region (Citrus, Hernando, Lake, Levy, Marion and Sumter Counties), the Floridan aquifer is at or near land surface, allowing rainfall to easily recharge (replenish) the aquifer system. In the central region (Hillsborough, Pasco, Pinellas and Polk Counties), the Floridan aquifer can be unconfined or confined (overlain by thick clays). Where the Floridan aquifer is confined, recharge to the aquifer from rainfall is low. In the southern region (Charlotte, DeSoto, Hardee, Highlands, Manatee and Sarasota Counties), the Floridan aquifer is confined. The ARI, which is a modification of the previously published Ground Water Index, is derived by comparing current ground-water levels with historical levels for 52 monitor wells located throughout the three regions of the District. Monitor wells with an adequate and reliable period-of-record to calculate weekly percentiles were selected for the network. For each well, the 16 th and 84 th percentiles ( low normal and high normal, respectively) were calculated for each week of the year for the period-ofrecord. The 16 th and 84 th percentiles were chosen to represent the low-normal and high-normal values, respectively, because they correspond to the statistical equivalent of one standard deviation above and above the average. The normal range is defined between the 16 th and 84 th percentiles. The normal range for the northern region is 0 to 4 feet, 0 to 6 feet for the central region and 0 to 8 feet for the southern region. To determine the ARI for a region, each well is compared to its respective low-normal value weekly, and the difference is calculated. The weekly differences are reduced to a monthly value for all of the monitor wells within a region, and the resulting ARI value represents how far water levels in the aquifer have to rise or fall to reach their respective low-normal value. As of August 28 th, the ARI was within the normal range in the southern region, and within the high normal range in the northern and central regions of the District. The ARI values in the northern and central regions were 5.60 and 8.03 feet, respectively, above the bottom of the normal range (or 16 th percentile). The ARI in the southern region was 5.65 feet above the bottom of the normal range.

47 AQUIFER RESOURCE INDEX* August Northern Region Feet, Relative to Base of Normal Range High** Normal Low Normal Sep-96 Sep-97 Sep-98 Sep-99 Sep-00 Sep-01 Sep-02 Sep-03 Feet, Relative to Base of Normal Range Central Region High Normal Low Normal Sep-96 Sep-97 Sep-98 Sep-99 Sep-00 Sep-01 Sep-02 Sep-03 Southern Region 20 Feet, Relative to Base of Normal Range High Normal Low Normal Sep-96 Sep-97 Sep-98 Sep-99 Sep-00 Sep-01 Sep-02 Sep-03 *Average Groundwater Level Relative to Low Normal ** High Normal is an Approximate Value

48 PUBLIC SUPPLY SURFACE WATER RESERVOIRS CITY OF TAMPA RESERVOIR (Hillsborough River Basin): The second largest public supply surface water facility is the Tampa Reservoir. Built in 1924, it is the main water supply for the City of Tampa and has a total storage capacity of 1.7 billion gallons (bg). The total usable volume is 1.4 bg, when the reservoir elevation is 22.5 feet NGVD. Located in Hillsborough County on the Hillsborough River, this in-stream reservoir has a depth that ranges between nine and 22 feet. Given this amount of water, it is estimated that a 15-day supply of water is available from this facility over an extended dry period. During periods of low water due to drought conditions, the facility is permitted to pump water from two alternate sources. The first of these two sources is the Tampa Bypass Canal. Water is pumped over the water control structure at S-161 into the Hillsborough River above the dam. The second source is Sulphur Springs, just downstream from the dam, where water is captured at the spring and pumped back behind the dam. Withdrawals from both sources are in strict accordance with pumpage schedules as outlined in the facility s water use permit. When water levels fall below 12 feet NGVD, water cannot be withdrawn because the reservoir level is below the intake pipes. The permitted average daily withdrawal for this facility is 82 mgd, with a permitted maximum daily withdrawal of 104 mgd. Currently, ground water wells are not used to augment this facility. The minimum producible level is 9.00 feet. PEACE RIVER RESERVOIR - PEACE RIVER/MANASOTA REGIONAL WATER SUPPLY AUTHORITY (Peace River Basin): Of the six surface-water public supply facilities within the District, PRMRWSA s Peace River facility has the only off-stream reservoir. Unlike other utilities, the daily river water pumpage is not a reflection of daily water consumed by the public. Built in 1980, the PRMRWSA facility ranks fifth in total volume storage, and supplies water to Charlotte County, City of North Port, and DeSoto County. While all of the available water produced for public supply comes from the Peace River, they have by far the most complicated system for insuring adequate supply throughout the year. The facility also uses an aquifer storage recovery (ASR) system for storing treated water pumped from the river. The current permit restrictions on the PRMRWSA facility state that they may not withdraw water from the Peace River if the river gauging station at Arcadia has declined below pre-established monthly levels. Also, withdrawals may not exceed 10 percent of the preceding day s flow level as calculated at the Peace River Arcadia gauge station. To the greatest extent possible, the PRMRWSA fills its reservoir and ASR facilities to full capacity to insure water is available during times they are not permitted to withdraw from the Peace River. The total size of the reservoir is approximately 85 acres and is 31 feet deep. Total storage capacity is approximately 625 mg. Average and maximum permitted withdrawal amounts from the Peace River are 32.7 and 90.0 mgd, respectively. The Peace River reservoir and ASR system are both permitted for an average withdrawal of 32.7 mgd. The minimum producible level is 8.00 feet. MANATEE RESERVOIR (Manasota Basin): Completed in 1967 by the damming of the Manatee River, the Manatee Reservoir is the largest of the six surface-water public supply facilities within the District. Located in Manatee County, this in-stream facility has a storage capacity of 7.5 bg. The service area of the Manatee reservoir is the unincorporated portions of Manatee County, the City of Palmetto and Anna Maria Island, and also the Sarasota SUD#1. This reservoir provides essentially all public supply for Manatee County, with the exception of the City of Bradenton. The total size of this reservoir is 1800 acres with an average depth of 15 feet. With the reservoir full, the facility has

49 approximately 220 days of available water supply. When the surface-water elevation drops below 21.0 feet, water cannot be withdrawn because levels are below the facility s intakes. The permitted average daily withdrawal for this facility is 34.9 mgd, with a permitted peak monthly quantity of 41.9 mgd. The minimum producible level is feet. EVERS RESERVOIR (Manasota Basin): The third largest public supply reservoir, with a total storage capacity of 1.5 bg, is the Evers Reservoir on the Braden River in Manatee County. This facility was constructed in 1935 and expanded in Its main service area is the City of Bradenton, and it also serves approximately 500 customers outside the city. The total size of the facility is 300 acres with an average depth of 12 feet. Water ceases to flow over the dam when the level falls below 3.84 feet NGVD. During the 1985 drought, while expansion of the facility was taking place, the water level dropped to one foot below sea level and demand was still met. Given a completely full reservoir, with no water going over the spillway, it is estimated the facility could supply water for approximately 260 days, with no input from rainfall. The permitted average daily withdrawal for this facility is 6.95 mgd, with a permitted peak monthly quantity of 8.13 mgd. Currently, ground-water wells are not used to augment this facility. SHELL CREEK RESERVOIR (Peace River Basin): Shell Creek Reservoir, located in Charlotte County, is the fourth largest surface water system within the District. This system was built in 1964 and services the City of Punta Gorda as well as unincorporated areas surrounding the city limits. The Shell Creek Reservoir is fed by two primary tributaries, Shell Creek from the east and Prairie Creek from the northwest. The total drainage area at Hendrickson Dam is 373 square miles. It has a surface area of 800 acres and depths of 10 to 12 feet. Total storage capacity is 765 mg. Even with this low volume of water, personnel at this facility estimate they have approximately 125 days of available supply with no input from rainfall. Water ceases to flow across the weir when surface elevations drop below 5.0 feet NGVD, and at 3.7 feet NGVD water quality becomes a major concern. When surface elevations drop below 1.75 feet NGVD, the water is below the intakes and withdrawal of water is not possible. The permitted average daily withdrawal by this facility is mgd, with a permitted peak monthly quantity of mgd. The minimum producible level is 1.70 feet.

50 Reservoirs Water-level data for the five reservoirs are obtained weekly from the USGS, Lake Manatee and Peace River/Manasota Regional Water Supply Authority. The weekly data are then reduced to a monthly average. The values reported are provisional and subject to revision. In August, three of the five reservoirs monitored for this report recorded water-level increases compared to the end of July. The Evers, Lake Manatee, and Shell Creek reservoirs posted average water-level increases of 0.37, 0.21, and 0.11 foot, respectively. The Hillsborough Reservoir showed no averaged change in water level compared to last month, while the Peace River reservoir recorded an average water level decrease of 0.43 foot.

51 SUMMARY OF WATER LEVELS IN WATER SUPPLY RESERVOIRS (ELEVATION IN FEET, NGVD) Change Change from Prior from Prior RESERVOIR July August August Month Year Evers City of Bradenton Hillsborough City of Tampa Lake Manatee Manatee County Peace River PRMRWSA Shell Creek City of Punta Gorda NGVD - National Geodetic Vertical Datum Reported data are provisional and subject to revision.

52 EVERS RESERVOIR City of Bradenton 6 Water Level Elevation (ft., NGVD) Water Level Elevation (ft., NGVD) Jan 98 Apr 98 Jan 98 Apr 98 Jul 98 Oct 98 Jan 99 Apr 99 Jul 99 Oct 99 Jan 00 Jul 98 Oct 98 Jan 99 Apr 99 Jul 99 Oct 99 Jan 00 May 00 May 00 Aug 00 Nov 00 TOP OF DAM Feb 01 May 01 Aug 01 CURRENT LEVEL HILLSBOROUGH RESERVOIR City of Tampa TOP OF SPILLWAY Aug 00 Nov 00 Feb 01 May 01 Aug 01 Nov 01 CURRENT LEVEL Nov 01 Mar 02 Jun 02 Sep 02 Dec 02 Mar 03 Jun 03 Sep 03 Mar 02 Jun 02 Sep 02 Dec 02 Mar 03 Jun 03 Sep 03

53 LAKE MANATEE RESERVOIR Manatee County 41 Water Level Elevation (ft. NGVD) Jan 98 Apr Jul 98 Oct 98 Jan 99 Apr 99 Jul 99 Oct 99 Jan 00 May 00 FULL LEVEL Aug 00 Nov 00 Feb 01 May 01 Aug 01 CURRENT LEVEL PEACE RIVER RESERVOIR Peace/Manasota Reg. Water Supply Nov 01 Mar 02 Jun 02 Sep 02 Dec 02 Mar 03 Jun 03 Sep 03 Water Level Elevation (ft. NGVD) Jan 98 Apr 98 Jul 98 Oct 98 Jan 99 Apr 99 Jul 99 Oct 99 Jan 00 FULL LEVEL May 00 Aug 00 Nov 00 Feb 01 May 01 Aug 01 CURRENT LEVEL Nov 01 Mar 02 Jun 02 Sep 02 Dec 02 Mar 03 Jun 03 Sep 03

54 Water Level Elevation (ft. NGVD) Jan 98 Apr 98 Jul 98 SHELL CREEK RESERVOIR City of Punta Gorda Oct 98 Jan 99 Apr 99 Jul 99 Oct 99 Jan 00 May 00 Aug 00 TOP OF WEIR Nov 00 Feb 01 May 01 Aug 01 Nov 01 CURRENT LEVEL Mar 02 Jun 02 Sep 02 Dec 02 Mar 03 Jun 03 Sep 03

55 APPENDICES

56 Rainfall percentiles by interval and region, inches. Rainfall Interval Region 10 TH Percentile (P10) 25 th Percentile (P25) 50 th Percentile (P50) 75 th Percentile (P75) 90 th Percentile (P90) Annual total Northern Annual total Central Annual total Southern Annual total District Dry season total Northern Dry season total Central Dry season total Southern Dry season total District Wet season total Northern Wet season total Central Wet season total Southern Wet season total District January total Northern January total Central January total Southern January total District February total Northern February total Central February total Southern February total District March total Northern March total Central March total Southern March total District April total Northern April total Central April total Southern April total District May total Northern May total Central May total Southern May total District June total Northern June total Central June total Southern June total District July total Northern July total Central July total Southern July total District August total Northern August total Central August total Southern August total District September total Northern September total Central September total Southern September total District October total Northern October total Central October total Southern October total District

57 Rainfall percentiles by interval and region, inches (continued). Rainfall Interval Region 10 TH Percentile (P10) 25 th Percentile (P25) 50 th Percentile (P50) 75 th Percentile (P75) 90 th Percentile (P90) November total Northern November total Central November total Southern November total District December total Northern December total Central December total Southern December total District Rainfall characterization ranges Characterization Range Corresponding Rainfall Percent of Normal (approximate) Very dry Less than the P10 rainfall Less than 80 percent of normal Drier than normal P10 to P25 rainfall 80 to 90 percent of normal Normal P25 to P75 rainfall 90 to 110 percent of normal Wetter than normal P75 to P90 rainfall 110 to 120 percent of normal Very Wet Greater than the P90 rainfall Greater than 120 percent of normal 53

58

59 Key to Representative Lake Monitoring Stations A Northern Region 15 Tsala Apopka at Inverness 52 Tsala Apopka at Floral City 113 Little Lake (Consuella) 120 Crews Lake 121 Hancock Lake 134 Big Fish Lake 175 Spring Lake (Hernando) 253 Lake Miona 257 Hunters Lake 420 Moon Lake 490 Tsala Apopka at Hernando 491 Lake Pasadena 499 Lake Panasoffkee 503 Lake Iola 533 Lake Lindsey B Tampa Bay Region 33 Lake Alice 47 Brooker Lake 77 Little Lake 128 Egypt Lake 130 Lake Harvey 131 Turkey Ford Lake 135 Platt Lake 139 Lake LeClare 141 King Lake 164 Lake Hiawatha 182 Camp Lake 191 Lake Linda 249 Deer Lake 274 Long Pond 292 Brant Lake 303 Carlton Lake 315 Mud (Walden) Lake 334 Lake Cooper 341 Lake Ann-Parker 380 Lake Thomas 402 Gornto Lake 422 Horse Lake 424 Lake Wimauma 425 Rainbow Lake 460 Calm Lake 472 Lake Keene 477 Church Lake 516 Lake Carroll 617 Lake Stemper (at structure) 624 Lade Padgett 1908 Crescent Lake 2481 Keystone Lake 2491 Bay Lake C Polk Uplands Region 8 Lake Alfred 14 Eagle Lake 16 Lake Helene 31 Lake McLeod 69 Lake Otis 97 Lake Garfield 100 Clearwater Lake 127 Lake Howard 169 Lake Juliana 251 Blue Lake South 370 Lake Ariana 390 Lake Conine 411 Lake Bonny 504 Lake Buffum 540 Lake Ruby 621 Lake Fannie (P-7) 1249 Scott Lake 2482 Lake Arietta 2484 Lake Hamilton D Lake Wales Ridge Region 65 Lake Clay 75 Lake Jackson 106 Trout Lake 186 Lake Annie 202 Lake Lotela 243 Lake Placid 294 Lake Letta 323 Crooked Lake 527 Starr Lake October 02 55

60 56

61 Key to Representative Stream Monitoring Stations A Northern Region 115 Withlacoochee River at Holder 122 Withlacoochee River at Trilby B Central Region 5 Pithlachascotee River 29 Hillsborough River 165 Anclote River C Southern Region 57 Myakka River 66 Josephine Creek 76 Manatee River 79 Peace River at Bartow 87 Little Manatee River 162 Alafia River 566 Peace River at Arcadia August 02 57

62 STREAM MONITORING STATIONS WITHLACOOCHEE RIVER (Northern Region) Total length: 157 miles Headwaters: NW Polk and southern Sumter Counties Elevation: 135 feet Tributaries: Little Withlacoochee, Big Gant Canal, Jumper Creek, Shady Brook, Outlet River of Lake Panasoffkee, Leslie Heifner Canal, Orange State Canal, Tsala Apopka Outfall Canal and Rainbow Springs. Mouth: Gulf of Mexico, Citrus County Average fall: 0.9 feet/mile Drainage area: 2000 square miles Holder Station County: Marion Period-of-record: 1928 Location: 38 miles upstream from mouth Avg daily discharge: cfs Runoff per year: inches Max of monthly avg discharge: cfs in 04/1960 Min of monthly avg discharge: cfs in 07/1992 Drainage area: 1825 square miles Trilby Station County: Hernando Period-of-record: 1928 Location: 93 miles upstream from mouth Avg daily discharge: cfs Runoff per year: 6.73 inches Max of monthly avg discharge: cfs in 09/1933 Min of monthly avg discharge: 6.1cfs in 07/1992 Drainage area: 570 square miles ANCLOTE RIVER (Central Region) Total length: 27.5 miles Headwaters: South-central Pasco County, west of Land O Lakes Elevation: 65 feet Tributaries: South Branch and Hollin Creek Mouth: Gulf of Mexico, Pasco County Average fall: 2.4 feet/mile Drainage area 113 square miles Elfers Station County: Pasco Period-of-record: 1946 Location: 16 miles upstream from mouth Avg daily discharge: 65.1 cfs Runoff per year: inches Max of monthly avg discharge: cfs in 09/1988 Min of monthly avg discharge: 1.4 cfs in 05/1981 Drainage area: 72.5 square miles 58