2010, 2012, 2016, and 2018 Integrated Reports Classified Use Support Evaluation. Compiled, Evaluated, and Written by R. W.

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1 2010, 2012, 2016, and 2018 Integrated Reports Classified Use Support Evaluation Compiled, Evaluated, and Written by R. W. Parachini December

2 2010, 2012, 2016, and 2018 Integrated Reports Classified Use Support Evaluation Executive Summary The EPA has issued guidance for the development of an Integrated Water Quality Monitoring and Assessment Report Integrated Report by the States. This report provides Colorado s assessments of water quality that were conducted during the past two years. Specifically, it compares water quality of surface waters within Colorado to the corresponding standards in order to assess the degree to which waters are in attainment of those standards. The Integrated Report provides the attainment status of all surface waters according to the five classified use categories adopted by the Colorado Water Quality Control Commission. Classified use categories are assigned to waterbodies based upon the actual uses occurring in the waterbody. Water quality standards are in place to ensure that the waterbody is supporting the assigned classified uses. The classified uses in Colorado are agriculture, aquatic life cold 1 & 2, aquatic life warm 1 & 2, domestic water supply, primary recreation, secondary recreation, and wetlands. The Colorado Water Plan Chapter 7.3 Water Quality describes the water quality and quantity integration goal for the state. The Water Quality Control Commission strategic water quality goal is: By 2050, Colorado s waters will fully support their classified uses, which may include drinking water, agriculture, recreation, aquatic life, and wetlands. Improved integration of water quality and quantity is required to address the WQCC overall goal for water quality. The Colorado Water Quality Forum has engaged in a topic evaluation process for several years that typically identified pollutant specific focus areas for work group efforts over the coming year. Recent additional discussions have been around the concept of developing a prioritization process to better identify potential forum and work group efforts. The Water Quality Control Division has developed the 2027 Water Quality Roadmap as a primary platform for this effort over the next 10 years. Forum level discussions of this effort may be better served at a state-wide or river basin scale rather than only at the pollutant level to address water quality issues. These realizations lead to the effort to evaluate classified use support at the statewide scale and at the river basin scale within and across reporting periods. River/stream miles and lake/reservoir acres in each classified use category were calculated as the respective percentage of the total statewide assessment miles and acre values. The values were then compared by classified use or reporting category within and across reporting periods. The percentages were also compared to the applicable WQCD or Clean Water program goal for water quality standards attainment. Classified use support data from the 2010, 2012, 2016, and 2018 Integrated Reports data was reviewed to evaluate the change in the various use classifications of river/stream miles and lake/reservoir acres over time. All use classifications showed a pronounced decrease in percent river/stream miles supported from 2010 to Lakes/reservoirs showed a more variable response in percent acres classified use support from 2010 to 2012, which also suggest a similar cause as in rivers/stream miles. This decrease may have been caused by WQCC actions such as additional classified uses, a classified use upgrade or downgrade, or increased available data and assessment and a change in assessment methodologies between periods. The agriculture, all aquatic life, and recreation use classifications then show a consistent increase in percent river/stream miles and lake/reservoir acres protected through This increase may have been caused by WQCC actions such as removal of a classified use or a classified use downgrade. Greater accuracy in water body size and increased 2

3 assessment of the recreation use also likely affected changes observed through the latest reporting cycle. The exception was domestic water supply, which showed considerable variability in protection ranging from a low of 11% in 2012 to high of 95% in A range around 60% was observed over the last 2 IR cycles and suggests that this may be a more accurate protection status. The 2010 to 2018 Integrated Reports data was reviewed by basin to evaluate the support of the various use classification of river/stream miles over time. The fully supporting reporting category (1) showed great variability across basins over time. The some uses supporting reporting category (2) shows variability over time, but has been decreasing across all basins over the last 10 years. The insufficient data/not assessed reporting categories (3 and 3a) show variability across basins over time, except the Rio Grande remaining steady in the low 20% range. The insufficient data - M&E list category (3b) has a more limited time period to evaluate from 2016 to 2018, which limits any trend observations. The TMDL completed and approved, impaired-no TMDL necessary, impaired naturally/impairment not caused by pollutant reporting categories (4a, 4b, and 4c) are not conducive to trend evaluation because of data limitations. The impaired; TMDL necessary reporting category (5) shows variability across river basins and time. The 2010, 2012, 2016, and 2018 Integrated Reports data was reviewed by basin to evaluate the support of the various use classification of lakes/reservoir acres over time. The fully supporting reporting category (1) showed greater variability over time within some basins than in others. The some uses supporting reporting category (2) show variability over time with the pattern for the majority of basins showing a percentage decrease and the remainder showing a percentage increase. The insufficient data/not assessed reporting categories (3 and 3a) show variability over time with four river basins showing an upward (negative) trend and three showing a downward (positive) trend. The TMDL completed and approved, impaired-no TMDL necessary, impaired naturally/impairment not caused by pollutant reporting categories (4a, 4b, and 4c) are not conducive to trend evaluation. This observation is because of minimal comparative data across time and very little change where it is available. The impaired; TMDL necessary reporting category (5) shows a general decreasing (positive) percentage across time for all basins. This decreasing trend may be the result of a change in applicable standards adopted by the WQCC or increased resources for lake/reservoir TMDL development. At the statewide level, the classified uses reporting categories percentages should be evaluated to determine potential causes such as standards development and other potential activities. At the basin level, the classified uses reporting a low fully supporting category status percentage should be evaluated to determine potential causes such as site-specific standards development actions, and standards implementation actions such as discharge permit issuance and TMDL completion activities. This two tier evaluation approach could prove to be a useful and successful means to identify important water quality issues that affect applicable classified use support. The causes of these trends may prove useful as information relative to future stakeholder resource commitments. The Water Quality Control Division developed the Colorado Nutrient Management Plan and 10- Year Water Quality Roadmap as part of the nutrients work group effort in The plan includes elements to address nutrient management framework, other standards development efforts, and treatment feasibility information through The plan will continue to be the primary approach for the WQCD to address the important issues. 3

4 A periodic classified use support evaluation could be an additional method to observe progress on deployment of the Colorado Nutrient Management Plan and 10-Year Water Quality Roadmap over the next 10 year period. It could also be used to evaluate state wide and river basin level classified use support in general. This evaluation may also prove to be a high level but simple method to evaluate progress towards the WQCC 2050 water quality goal identified in the Colorado Water Plan. Additional refinement of the cause/effect relationship between standards development and standards implementation and the classified use support percentages over time is recommended to increase the utility and applicability of the evaluation results. 4

5 2010, 2012, 2016, and 2018 Integrated Reports - Water Quality Status Summary Integrated Reporting Guidance Background Information The following text in this section is a select summary compilation of the 2010, 2012, 2016, and 2018 Integrated Reports. The EPA has issued guidance for the development of an Integrated Water Quality Monitoring and Assessment Report (Integrated Report (IR)) by the states. This guidance requires that states integrate their Water Quality Inventory Report (305(b) Report) and their Impaired Waterbodies List (303(d) list). These components and others make up the IR. The IR is intended to provide an effective tool for maintaining high quality waters and improving the quality of waters that do not attain water quality standards. The integrated report also provides water resources managers and citizens with detailed information regarding the following: Progress towards achieving comprehensive assessment of all waters; Water quality standards attainment status; Methods used to assess water quality standards attainment status; Additional monitoring needs and schedules; Pollutants and water bodies requiring TMDLs; Pollutants and waterbodies requiring alternative pollution control measures; Management strategies (including TMDLs) under development to attain water quality standards; and TMDL development schedules. The IR provides Colorado s assessments of water quality that were conducted during the past two years. Specifically, it compares water quality of surface waters within Colorado to the corresponding standards in order to assess the degree to which waters are in attainment of those standards. The IR provides the attainment status of all surface waters according to the five reporting categories described later. This report also includes a description of groundwater quality activity and links to agencies involved with groundwater monitoring. The 2012 IR submittal was an updated version of the 2010 report. Colorado had to defer the 2014 IR due to resource constraints. This 2016 IR covers both the 2014 and 2016 reporting cycles. The 2018 IR covers only the 2018 reporting cycle. Three significant changes were incorporated into the 2018 IR. First, greater accuracy in water body size was achieved. Enhancements in the NHD/GIS layers improved the accuracy of stream miles and lake sizes in Colorado. Second, increased assessment of the recreation use was implemented. For the first time, ph and E. coli measurements were used to determine whether the recreation use was attained. This resulted in an increased number of river/stream miles. The third was related to lead for the Safe Drinking Water Program. Colorado Use Classifications Background Information The Clean Water Act at Section 101(a)(2) requires that all waters be suitable for the protection and propagation of fish, shellfish and wildlife and for recreation in and on the water unless it is demonstrated that the use is not attainable. Classified use categories are assigned to water bodies based upon the actual uses occurring in the waterbody. Water quality standards are then developed to ensure that the waterbody is attaining the classified uses assigned. The classified uses and definitions in Colorado are: Agriculture. These surface waters are suitable or intended to become suitable for irrigation of crops usually grown in Colorado and which are not hazardous as drinking water for livestock. 5

6 Aquatic Life Cold-1. These are waters that (1) currently are capable of sustaining a wide variety of cold water biota, including sensitive species, or (2) could sustain such biota but for correctable water quality conditions. Waters are considered capable of sustaining such biota where physical habitat, water flows or levels, and water quality conditions result in no substantial impairment of the abundance and diversity of species. Aquatic Life Cold-2. These are waters that are not capable of sustaining a wide variety of cold water biota, including sensitive species, due to physical habitat, water flows or levels, or uncorrectable water quality conditions that result in substantial impairment of the abundance and diversity of species. Aquatic Life Warm-1. These are waters that (1) currently are capable of sustaining a wide variety of warm water biota, including sensitive species, or (2) could sustain such biota but for correctable water quality conditions. Waters are considered capable of sustaining such biota where physical habitat, water flows or levels, and water quality conditions result in no substantial impairment of the abundance and diversity of specifies. Aquatic Life Warm-2. These are waters that are not capable of sustaining a wide variety of warm water biota, including sensitive species, due to physical habitat, water flows or levels, or uncorrectable water quality conditions that result in substantial impairment of the abundance and diversity of species. Domestic Water Supply. These surface waters are suitable or intended to become suitable for potable water supplies. After receiving standard treatment (defined as coagulation, flocculation, sedimentation, filtration, and disinfection with chlorine or its equivalent) these waters will meet Colorado drinking water regulations and any revisions, amendments, or supplements thereto. Primary Recreation. These surface waters are used for primary contact recreation or have been used for such activities. These surface waters are use for primary contact recreation. Primary contact recreation means recreational activities where the ingestion of small quantities of water is likely to occur. Such activities include but are not limited to swimming, rafting, kayaking, tubing, windsurfing, water-skiing, and frequent water play by children. Secondary Recreation. These surface waters have the potential to be used for primary contact recreation, or are not suitable or intended to become suitable for primary contact recreation uses, or are surface waters whose quality is to be protected at the same level as existing primary contact use waters, but for which there has not been a reasonable level of inquiry about existing recreational uses and no recreation use attainability analysis has been completed. Wetlands. A general definition is that these surface waters are areas that are inundated by surface or groundwater at a frequency and duration to support a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands in Colorado can be defined as tributary, created, or compensatory and the applicable standards may be numeric or narrative pending on the designated type of wetland assigned. Colorado Water Plan - Water Quality and Quantity Integration Goal Background Information The Colorado Water Plan (CWP) Chapter 7.3 Water Quality describes the water quality and quantity integration goal developed as part of the plan. Improved integration of water quality and quantity planning and management activities is critical as Colorado plans for its water future. Opportunities to address existing water quality impacts and minimize future impacts were identified as a priority to ensure residents and visitors continue to have access to safe and clean water. The need to strike a balance between increasing quantity demands with water quality protection and restoration requires on-going dialogue with all interests and 6

7 collaboration at all levels of government. The CWP offers a framework for continuing and improving the quality and quantity conversations. The Water Quality Control Commission (WQCC) strategic water quality goal in the CWP is: By 2050, Colorado s waters will fully support their classified uses, which may include drinking water, agriculture, recreation, aquatic life, and wetlands. Improved integration of water quality and quantity is required to address the WQCC overall goal for water quality. The WQCC the developed a quality and quantity integration goal in the CWP as follows: Recognizing the inter-relationship between quality and quantity, strategies designed to meet Colorado s current and future consumptive, recreational and environmental water needs will incorporate, as a key objective, the protection and restoration of water quality. The advancement of this goal will require substantial effort on the part of basin roundtables, water users, project proponents, state agencies, local interests, and individual dischargers. Colorado Water Quality Forum Focus Background Information The Colorado Water Quality Forum has engaged in a topic evaluation process for several years that typically identified pollutant specific focus areas for work group efforts over the coming year. Recent additional discussions have been around the concept of developing a prioritization process to better identify potential forum and work group efforts. Forum level discussions of this effort may be better served at a state-wide or river basin scale rather than only at the pollutant level to address water quality issues. These realizations lead to the effort to evaluate classified use support at the statewide scale and at the river basin scale within and across reporting periods. This effort starts by summarizing the most recent 2018 Integrated Report as follows Integrated Report Assessment Results Summary For the assessment cycle, over 92,537 river miles and more than 270,195 lake acres were assessed. For Colorado streams and rivers (Table 1), over 53,418 miles supported all classified uses and approximately 487 miles supported at least one classified use. A total of 25,484 miles were found to be impaired and require a TMDL analysis to be developed. The following table shows the percentages of assessed and attaining river and stream miles. Table 1: Proportion of River and Stream Miles Supporting Uses Use Supporting Not supporting Insufficient data Not assessed Aquatic Life 76.0% 11.7% 4.9% 7.4% Domestic water supply 58.6% 27.3% 6.6% 7.5% Recreation 88.5% 1.9% 2.4% 7.3% Agriculture 92.1% 0.5% 0.0% 7.5% All uses 80.3% 9.1% 3.2% 7.4% The most common causes of impairments in the 2018 listing cycle were arsenic, selenium, copper, E. coli and total recoverable iron. The primary causes for non-attainment of the aquatic life use was selenium, for non-attainment of the water supply use was arsenic, and for non-attainment of the recreation use was E. coli. Standards associated with the agricultural use are typically less stringent compared to standards protective of both aquatic 7

8 life and water supply uses. Therefore, non-attainment of the agricultural use alone is not common. The following table shows the percentages of assessed and attaining lake and reservoir acres. Table 2: Proportion of Lake and Reservoir Acres Supporting Uses Use Supporting Not supporting Insufficient data Not assessed Aquatic Life 34.8% 22.6% 3.1% 39.5% Domestic water supply 41.7% 12.3% 0.9% 45.0% Recreation 60.6% 0.0% 0.0% 39.4% Agriculture 59.3% 0.0% 0.0% 40.7% All uses 49.3% 8.7% 1.0% 41.1% The primary causes of impairments to lakes and reservoirs in the 2018 listing cycle were dissolved oxygen, fish tissue mercury, ph and selenium. All the identified causes are associated with exceedances of the aquatic life use standards. For the assessment of water supply use, the most common impairment in lakes and reservoirs was caused by arsenic. Additional Classified Use Support Evaluation Evaluation Methodology An additional compilation of the 2010, 2012, 2016, and 2018 Integrated Reports data was conducted. Rivers/streams and lakes/reservoirs use support data was tabulated and evaluated in the following appendix tables: Table to 2018 State Wide Classified Use Support Status. The IR classified use reporting categories (fully supporting, not supporting, not assessed, and insufficient information/data) are tabulated by IR year and use classification by calculating the percent of total river/stream miles and lakes/reservoirs acres for each individual use. This matrix provides a state wide overview of classified use support within IR periods and over time. The percentages were then compared to the applicable WQCD or Clean Water (CW) program goals for water quality standards attainment by using a color coded scheme to highlight a range of good to poor classified use support. Table to 2018 River Basin River/Stream Miles IR Reporting Categories Status. The IR classified use reporting categories for river/stream miles (fully supporting, some uses supporting, insufficient data/not assessed, TMDL completed and approved, impaired no TMDL necessary, impaired naturally/not caused by pollutant, and impaired; TMDL necessary) are tabulated by IR year and river basin by calculating the percent of total river/stream miles for each basin. This matrix provides a basin level overview of river/stream miles classified use support within IR periods and over time. The percentages were then compared to the WQCD or CW program goals for water quality standards with a color coded scheme to highlight a range of good to poor classified use support. Table to 2018 River Basin Lake/Reservoir Acres IR Reporting Categories Status. The IR reporting categories (fully supporting, some uses supporting, insufficient data/not assessed, TMDL completed and approved, impaired no TMDL necessary, impaired naturally/not caused by pollutant, and impaired; TMDL necessary) are tabulated by IR year and river basin by calculating percent of total lake/reservoir acres for each river basin. This matrix provided the basin level overview of lake/reservoir acres classified use support within IR periods and over time. The percentages were then compared to the applicable WQCD or Clean Water (CW) program goals for water quality standards attainment with a color coded scheme to highlight a range of good to poor classified use support. 8

9 State Wide Classified Use Support Evaluation Classified use support by IR period and reporting category percentages were evaluated using river/stream miles and lake/reservoir acres as shown in Table IR Reporting Category Status The percentage of rivers and stream miles fully supporting classified uses ranged from a high in the mid 90% range for agriculture, domestic water supply, and secondary contact recreation to a low of 39% for aquatic life warm-1. Recreation primary contact and aquatic life cold-1 were lower in the mid 80% range. Aquatic life cold-1 was in the mid 60% range and warm-2 in the upper 50% range. The percentage of lakes and reservoir acres fully supporting classified uses ranged from the high 90% range for agriculture, domestic water supply, and primary contact recreation to 10% for aquatic life warm-2. Secondary contact recreation was in the mid 80% range. Aquatic life cold-2 was close to 70%, with aquatic life cold-1 in the mid 30% range, and warm-1 in low 20% range IR Reporting Category Status The percentage of rivers and stream miles fully supporting classified uses ranged from a high of 84% for secondary recreation to a low of 18% for aquatic life warm-1. Recreation primary contact, agriculture, and aquatic life cold-1 were lower in the 70% range, with all other uses in the 50% range. When compared to the WQCD/CW program water quality standards attainment goal of 60%, the agriculture, aquatic life cold-1, and recreation primary contact classified uses for rivers/stream miles exceeded the goal. The percentage of lakes and reservoir acres fully supporting classified uses ranged from a high of 49% for domestic water supply to a low of 1% for aquatic life warm-2. Agriculture, recreation primary contact, and aquatic life cold-1 were lower in the 40% range, followed by aquatic life warm-1 in the 30% range, and all other uses in the teen s percent range. When compared to the WQCD/CW program water quality standards attainment goal of 40%, the agriculture, domestic water supply, and recreation primary contact classified uses for both lakes/reservoir acres exceeded the goal IR Reporting Category Status The percentage of rivers and stream miles fully supporting classified uses ranged from a high of 91% for agriculture to a low of 44% for recreation secondary contact. Aquatic life warm-2 was in the low 80% range, followed by aquatic life cold-1 & 2, recreation primary contact, and domestic water supply in the 60% range, and aquatic life warm-1 in the upper 40% range. When compared to the WQCD/CW program water quality standards attainment goal of 70%, the agriculture and aquatic life warm-2 classified uses for rivers/stream miles exceeded the goal. The percentage of lakes and reservoir acres fully supporting classified uses ranged from a high of 57% for agriculture to a low of 1% for recreation secondary contact. Domestic water supply and aquatic life cold-1 were lower in the 40% range, followed by aquatic life warm-1 & 2 in the 20% range, and recreation primary contact, aquatic life cold-1 in the teens to single digit percent range. When compared to the WQCD/CW program water quality standards attainment goal of 40%, the agriculture, aquatic life cold-1 and domestic water supply classified uses for lakes/reservoir acres exceeded the goal. 9

10 2018 IR Reporting Category Status The percentage of rivers and stream miles fully supporting classified uses ranged from a high of 92% for agriculture and secondary contact recreation to a low of 40% for aquatic life warm- 1. Primary contact recreation and aquatic life warm-2 were in the mid to upper 80% range, followed by aquatic life cold-1 & 2 in the low 70% range, domestic water supply in the high 50% range, and aquatic life warm-1 in the upper 40% range. When compared to the WQCD/CW program water quality standards attainment goal of 70%, the agriculture and aquatic life cold- 1 and warm-1, and recreation primary and secondary contact classified uses for rivers/stream miles exceeded the goal. The percentage of lakes and reservoir acres fully supporting classified uses ranged from a high of 63% for recreation primary contact to a low 1% for recreation secondary contact. Agricultural use followed closely at 59%. Aquatic life cold-1 and domestic water supply were in the low to mid 40% range, followed by aquatic life warm-1 & 2 in the mid 20% range. Aquatic life cold-1 was in the 4% range. When compared to the WQCD/CW program water quality standards goal of 40%, the agriculture, aquatic life cold-1, domestic water supply, and recreation primary contact classified uses for lakes/reservoir acres exceeded the goal State Wide Classified Use Support Status Classified use support data from the 2010, 2012, 2016, and 2018 Integrated Reports data was reviewed in Table 3 to evaluate the change in the various use classifications of river/stream miles and lake/reservoir acres over time. All use classifications showed a pronounced decrease in percent river/stream miles supported from 2010 to This decrease may have been caused by WQCC actions such as additional classified uses, a classified use upgrade or downgrade, or increased available data and assessment and a change in assessment methodologies between periods. The agriculture, all aquatic life, and recreation use classifications then show a consistent increase in percent river/stream miles use support through This increase may have been caused by WQCC actions such as removal of a classified use or a classified use downgrade. The exception was domestic water supply, which showed considerable variability in classified use support ranging from a low of 11% in 2012 to high of 95% in A range around 60% was observed over the last 2 IR cycles and suggests that this may be a more accurate classified use support status range. A relatively low use support status of the aquatic life warm-1 use around 40% was observed. A large fluctuation of the recreation secondary contact use from 44% in 2016 to 93% in 2018 was also observed. As noted in the previous discussion of the 2018 IR, greater accuracy in water body size and increased assessment of the recreation use likely affected changes observed through the latest reporting cycle. Lakes/reservoirs showed a more variable response in percent acres classified use support from 2010 to 2012, which also suggest a similar cause as in rivers/stream miles. The agriculture, aquatic life cold-2, warm-2, domestic water supply, and recreation primary and secondary contact all showed a large decreasing classified use support change, but the remainder showed small percentage increases. The agriculture, aquatic life cold-1 and warm- 2, and recreation primary contact classified uses then show a consistent increase in percent lake/reservoir acres use support through The aquatic life cold-2 and recreation secondary contact classified uses showed significant decrease through 2018, while aquatic warm-1 and domestic water supply showed a smaller decrease. All classified use percentages appear to be stabilizing between the 2016 and 2018 periods and can be confirmed with the 10

11 2020 IR assessments. Again, the changes noted in the 2018 IR likely affected changes observed through the latest reporting cycle. At the statewide level, the classified uses reporting categories percentages should be evaluated to determine potential causes such as standards development and other potential activities. The causes of these trends may prove useful as information relative to future stakeholder resource commitments to 2018 River Basin River/Stream Miles IR Reporting Categories Status There are 7 basin systems in Colorado based on the WQCC water quality standards basins: Arkansas, upper Colorado and N. Platte, San Juan and Dolores, Gunnison and lower Dolores, Rio Grande, S. Platte, and lower Colorado. Table 4 presents a summary of the IR reporting categories by IR period by percent river basin river/stream miles for review within and across time periods. An evaluation of the Gunnison & lower Dolores and lower Colorado basins was not possible because of differing assessment areas from 2010 to This evaluation could be completed but not without additional effort by WQCD to compile the data into a new format IR Classified Use Support Basin River/Stream Miles Status The percentage of fully supporting classified uses (category 1) across basins ranged from a high of 54% for the Rio Grande to a low of 29% for the Arkansas basin. The upper Colorado & N. Platte and San Juan & Dolores basins were in the mid 40% range, followed by the S. Platte in the low 30% range IR Classified Use Support by Basin River/Stream Miles Status The percentage of fully supporting classified uses within basins ranged from a high of 84% for the upper Colorado & N. Platte to a low of 29% for the lower Colorado basin. The Arkansas and Rio Grande basins were in the low 70% range, followed by the Gunnison & lower Dolores and San Juan & Dolores in the 50% range, the S. Platte in the low 30% range, and the lower Colorado in the high 20% range. When compared to the WQCD/CW program water quality standards attainment goal of 60%, the Arkansas, upper Colorado & N. Platte, and Rio Grande basins met or exceeded the goal IR Classified Use Support by Basin River/Stream Miles Status The percentage of fully supporting classified uses within basins ranged from a high of 54% for the upper Colorado & N. Platte to a low of 7% for the Arkansas basin. The lower Colorado and Gunnison and lower Dolores basins were in the low 50% range, followed by the San Juan & Dolores in the mid 30% range, with the Rio Grande and S. Platte basins in the mid teens percent range. When compared to the WQCD/CW program standards attainment goal of 70%, no basins met the goal IR Classified Use Support by Basin River/Stream Miles Status The percentage of fully supporting classified uses within basins ranged from a high of 75% for the S. Platte to a low of 28% for the Arkansas basin. The lower Colorado basin followed closely at 74%, with the upper Colorado & N. Platte basin in the high 60% range. The San Juan & Dolores and Gunnison & lower Dolores were in the 50% range and the Rio Grande in the high 40% range. When compared to the WQCD/CW program water quality standards attainment goal of 70%, the S. Platte and lower Colorado met the goal, with the upper Colorado & N. Platte close at 68%. 11

12 River Basin Reporting Category River/Stream Miles over Time The 2010, 2012, 2016, and 2018 Integrated Reports data in Table 4 was reviewed by basin to evaluate the support of the various reporting categories of river/stream miles over time. The fully supporting reporting category (1) showed great variability across basins over time. The Arkansas basin was the prime example ranging from 71% in the 2012 IR to 7% in the 2016 IR. The upper Colorado & N. Platte basin showed a general increasing trend from 47% to 68%. The San Juan & Dolores basin showed a similar trend, ranging from 37% in 2012 to 54% in The Gunnison & lower Dolores showed an increasing trend over a small range from 50% to 57%. The Rio Grande basin showed a decreasing trend, ranging down from 70% to 19%. The S. Platte showed the greatest increase over time, ranging up from 14% to 75%. The lower Colorado showed a consistent upward trend, ranging from 29% to 74%. The difference across IR periods could be caused by many factors but is likely driven by classified use and applicable standards changes (i.e. temperature and arsenic) adopted by the WQCC in the basins between basic standards rulemaking hearings. The some uses supporting reporting category (2) shows variability over time, but has been decreasing across all basins over the last 10 years. The 2018 IR shows the Arkansas, upper Colorado & N. Platte, and S. Platte basins at a very low 1%, while all others were at 0%. This downward trend is positive and likely indicative of increased data collection and assessment efforts over the 10 year period, which results in a more comprehensive and accurate classified use support determination. The insufficient data/not assessed reporting categories (3 and 3a) show variability across basins over time, except the Rio Grande remaining steady in the low 20% range. The insufficient data - M&E list category (3b) has a more limited time period to evaluate from 2016 to 2018, which limits any trend observations. The low 2018 percentages are likely supported by the increase data collection and assessment efforts over time. The TMDL completed and approved, impaired-no TMDL necessary, impaired naturally/impairment not caused by pollutant reporting categories (4a, 4b, and 4c) are not conducive to trend evaluation. This observation is because of minimal comparative data across time in several basins and very little change where it is available. The impaired; TMDL necessary reporting category (5) shows variability across river basins and time. The Arkansas showed the greatest change over time by increasing from the low teens percent in 2010 and 2012 to 65% in The upper Colorado & N. Platte, S. Platte, and lower Colorado basins show the most stability at 13 to 14% range. The San Juan & Dolores, Gunnison & Lower Dolores, and Rio Grande basins all show increasing percentages over time ranging from 17% to 24%. The difference across assessment years and basins could be caused by many factors but is likely driven by classified use and applicable standards changes (i.e. temperature and arsenic) adopted by the WQCC in the basin control regulations between basic standards rulemaking hearings. Increased water quality impairment could be driven by an increase in river/stream segmentation adopted by the WQCC over this time period. Other contributing factors could be the past and current resource constraints applied to TMDL development and implementation between point and nonpoint source contributions. At the basin level, the classified uses reporting a low fully supporting category (1) status percentage could be evaluated to determine potential causes such as site-specific standards development actions, and standards implementation actions such as discharge permit 12

13 issuance and TMDL completion activities. The causes of these trends may prove useful as information relative to future stakeholder resource commitments to 2018 River Basin Lake/Reservoir Acres IR Reporting Categories Status The 2010, 2012, 2016, and 2018 Integrated Reports data in Table 5 was reviewed by basin to evaluate the support of the various use classification of lake/reservoir acres over time. An evaluation of the Gunnison & lower Dolores and lower Colorado basins was not possible because of differing assessment areas from 2010 to This evaluation could be completed but not without additional effort by WQCD to compile the data into a new format IR Classified Use Support by Basin Lakes/Reservoirs Acres Status The percentage of fully supporting reporting (category 1) across basins ranged from a high of 52% for the upper Colorado & N. Platte to a low of 16% for the Arkansas basin. The San Juan & Dolores and Rio Grande basins were around the 10% range, followed by the S. Platte at 0% IR Classified Use Support by Basin Lakes/Reservoirs Acres Status The percentage of fully supporting classified uses across basins ranged from a high of 68% for the Gunnison & lower Dolores to a low of 0% for the lower Colorado basin. The upper Colorado & N. Platte basin was in the mid 20% range, followed by the Arkansas and S. Platte in the teens percent range, and the San Juan & Dolores and Rio Grande basins in the single digit percent range. When compared to the WQCD/CW program water quality standards attainment goal of 40%, only the Gunnison & lower Dolores exceeded the goal IR Use Support by Basin Lakes/Reservoirs Acres Status The percentage of fully supporting classified uses across basins ranged from a high of 36% for the upper Colorado & N. Platte to a low 1% for the Arkansas and San Juan & Dolores basins. The Rio Grande and lower Colorado basins were in the teens percent, followed by all remaining basins in the single digit percent range. When compared to the WQCD/CW program water quality standards attainment goal of 40%, no basins met the goal IR Use Support by Basin Lakes/Reservoirs Acres Status The percentage of fully supporting classified uses across basins ranged from a high of 38% for the S. Platte to a low of 8% for the San Juan & Dolores basin. The upper Colorado & N. Platte followed closely at 37%, with the Rio Grande basin in the low 30% range. The Arkansas was in the high 20% range, with the lower Colorado in low 20% range and the Gunnison and lower Dolores in the high teen s percent range. When compared to the WQCD/CW program water quality standard attainment goal of 40%, no basins met the goal, but the S. Platte basin was close at 38%. River Basin Reporting Category Lake/Reservoir Acres over Time The 2010, 2012, 2016, and 2018 Integrated Reports data in Table 5 was reviewed by basin to evaluate the support of the various reporting categories of lake/reservoir acres over time. The fully supporting reporting category (1) showed greater variability over time within some basins than in others. The S. Platte basin increased from 0% to 38%, the Rio Grande from 9% to 31%, the lower Colorado from 0% to 21%, and the Arkansas from 16% to 27%. The Gunnison & lower Dolores decreased from 68% to 18%, the upper Colorado & N. Platte from 52% to37%, and the San Juan & Dolores from 11% to 8%. The difference across assessment years could be caused by many factors but is likely driven by classified use and applicable standards changes (i.e. temperature and arsenic) adopted by the WQCC in the basin control regulations between basic standards rulemaking hearings. Another potential factor could be the advances in 13

14 lakes/reservoirs mapping technology between IR periods that increased the number of acres assessed. The some uses supporting reporting category (2) show variability over time with the pattern for the Arkansas, San Juan & Dolores, Gunnison and lower Dolores, Rio Grande, S. Platte, and lower Colorado showing a percentage decrease and the upper Colorado & N. Platte showing a percentage increase. The downward trend is a positive indicator and likely the result of increased data collection and assessment efforts over time, which results in a more comprehensive use support determination. The upward trend in the upper Colorado & N. Platte could not be explained. The insufficient data/not assessed reporting categories (3 and 3a) show variability over time with the Arkansas basin showing an increase to 35% and then down to 29%, the upper Colorado & N. Platte from 26% to 44% to 33%, the Gunnison & lower Dolores 21% to 74%, and the Rio Grande from 33% to 66% to 42%. This upward trend is not a positive direction and likely caused by improved mapping technology that includes more water bodies. The San Juan & Dolores basin decreased from 34% to 17%, the S. Platte from 60 to 43%, and the lower Colorado from 93% to 73%. The downward trend is not a negative direction and likely the result as in category (2), the increased data collection and assessment efforts over time. The insufficient data - M&E list category (3b) has a general flat or slight decreasing percentage over time across all basins. Additional time and data evaluation is necessary to determine any definitive trends. The TMDL completed and approved, impaired-no TMDL necessary, impaired naturally/impairment not caused by pollutant reporting categories (4a, 4b, and 4c) are not conducive to trend evaluation. This observation is because of minimal comparative data across time and very little change where it is available. The one noteworthy observation is that of a 26% increase in category 4a (TMDL completed and approved) in the San Juan & Dolores basin. The cause of this large increase would be of interest to identify. The impaired; TMDL necessary reporting category (5) shows a general decreasing but positive percentage across time for all basins. The San Juan & Dolores basin showed the largest decrease from 54% to 21%, followed by the Rio Grande from 38% to 11%, the upper Colorado & N. Platte from 19% to 0%, and the Arkansas from 58% to 44%. All remaining basins showed a small decrease over time and in the low teens to single digit percent range. This positive trend may be the result of a change in applicable standards adopted by the WQCC or increased resources for lake/reservoir TMDL development. At the basin level, the classified uses reporting a low fully supporting (category 1) status percentage should be evaluated to determine potential causes such as site-specific standards development actions, and standards implementation such as discharge permit issuance and TMDL completion activities. The causes of these trends may prove useful as information relative to future stakeholder resource commitments. Next Steps The Water Quality Control Division developed the Colorado Nutrient Management Plan and 10- Year Water Quality Roadmap as part of the nutrients work group effort in The plan includes the following elements: Provides an overview of Colorado s current nutrient management framework; 14

15 Discusses plans for further reducing nutrients from point source and nonpoint sources; Outlines the major milestones the division, Water Quality Control Commission, and stakeholders will need to undertake over the next 10 years to implement the plan; Provides an overview of how Colorado will continue to make progress on revising nutrient standards; Summarizes other standards development efforts through 2027; Details plans for developing treatment feasibility information over the next 10 years; and Establishes how the division will monitor and measure progress related to nutrients controls. The plan was modeled after the 2011 memo from the Environmental Protection Agency s (EPA) Nancy Stoner titled Working in Partnership with States to Address Phosphorus and Nitrogen Pollution through Use of a Framework for State Nutrient Reductions and EPA s 2016 memo from Joel Beauvais titled Renewed Call to Action to Reduce Nutrient Pollution and Support for Incremental Actions to Protect Water Quality and Public Health. After the October 2017 rulemaking, the division made this plan and 10-year water quality roadmap a division policy. The plan and roadmap has been accepted by the WQCC because of its importance as the primary tactic to resolve multiple standards development issues and the subsequent implementation challenges. The plan will continue to be the primary approach for the WQCD to address these important issues. Conclusions A periodic classified use support evaluation could be an additional method to observe progress on deployment of the Colorado Nutrient Management Plan and 10-Year Water Quality Roadmap over the next 10 year period. It could also be used to evaluate state wide and river basin level classified use support in general. This evaluation may also prove to be a high level but simple method to evaluate progress towards the WQCC 2050 water quality goal identified in the Colorado Water Plan. Additional refinement of the cause/effect relationship between standards development and standards implementation and the classified use support percentages over time is recommended to increase the utility and applicability of the evaluation results. 15