Colorado's 2022 Integrated Report
Prepared Pursuant to Sections 303(d), 305(b), and 314 of the Clean Water Act
Welcome!
Our mission
The Water Quality Control Division (division) monitors and reports on the quality of state waters to prevent water pollution, protect, restore and enhance the quality of surface and groundwater while ensuring that all drinking water systems provide safe drinking water. Our mission is "to protect and restore Colorado's water quality for public health, the environment, and future generations."
About this Story Map
This is the story of Colorado's 2022 Integrated Water Quality Monitoring and Assessment Report. The division created this Story Map as a way to report on the status of Colorado's streams and lakes in an easy-to-understand format that informs and engages the audience. This interactive Story Map is a simplified version of the written report. See the 2022 Integrated Report for more detailed information.
How to use this Story Map
To view this Story Map, scroll down through the content or use the top menu to jump to a specific topic of interest. Figures that are located within the story can be expanded by clicking or tapping on the image. When you see words with a red underline, click on the word(s), and it will take you to a website or document.
For a better user experience, we recommend using a desktop or laptop computer. Some of the interactive features work best on these devices. If you have trouble viewing the Story Map, try using a different web browser or changing the browser zoom level.
Contact us
For more information on the Integrated Report, please contact Skip Feeney by email at skip.feeney@state.co.us
Introduction
What is the Integrated Water Quality Monitoring and Assessment Report?
The federal Clean Water Act requires that states report on the quality of the nation’s waters every two years to the Environmental Protection Agency (EPA). These requirements are in Sections 305(b) and 303(d) of the Clean Water Act. Section 305(b) requires that states submit a comprehensive water quality report to the EPA every other year. Section 303(d) requires states to develop a list of waterbodies that do not meet water quality standards. The Integrated Report combines the reporting requirements of the Clean Water Act into one report.
Colorado's Integrated Report provides statewide water quality assessment summaries and the status of all surface waters according to five reporting categories. The report also provides information on the division's water quality programs that work to restore and protect Colorado's waters.
How does the Integrated Report fit into the Clean Water Act?
The Clean Water Act requires states to establish water quality standards for all state waters. These standards are set to protect the uses that are designated for each waterbody.
Section 303(d) of the Clean Water Act requires states to evaluate all available water quality data and information to develop a list of waters that do not meet water quality standards.
The information contained in the Integrated Report is used to set priorities and implement water quality controls and protection activities. States are required to assess and resubmit their list of impaired waters every two years, meaning impaired waters continue to be monitored and assessed until assigned water quality standards are met.
What is the Section 303(d) List of Impaired Waters?
Section 303(d) of the Clean Water Act requires states to submit a list of impaired waters every two years. Impaired waters are waterbodies that do not meet water quality standards. This list of waters is called the 303(d) List of Impaired Waters (also known as the "303(d) List").
The Monitoring and Evaluation List is an additional list of waters where there is reason to suspect water quality problems, but there is uncertainty regarding one or more factors such as the representative nature of the data. Both lists are adopted by the Water Quality Control Commission (commission) as Regulation 93 through a public rulemaking hearing process. An electronic version of Regulation 93 is available on the Regulation 93 dashboard web page .
Segments are included on the Section 303(d) List of Impaired Waters based on an evaluation of biological, chemical, or physical data demonstrating non-attainment of standards. This process of evaluating data/information for each waterbody is called an assessment. The assessment practices used by the division to determine the attainment status of waters in the state are detailed in a document called the Listing Methodology . The Listing Methodology is approved by the commission through a public administrative action hearing process. Like the Section 303(d) List and Monitoring and Evaluation List, the Listing Methodology is revisited every two years.
How are waterbodies removed from the 303(d) List?
In an effort to report progress in restoring waters, the EPA recommends that states document the status of segments that have been removed from the 303(d) List. Below is the list of reasons for removing waterbodies from the 303(d) List.
- The state determines the water quality standard is being met
- A TMDL is approved or an alternative pollution control plan is developed
- The applicable water quality standards are attained due to restoration activities, changes in standards, new assessment methods, or the original basis for the listing was incorrect
The removal of waterbodies and pollutants from the 303(d) List is considered appropriate in instances where new information is developed that indicate water quality standards are being met and/or designated uses attained. The process for delisting segments from the 303(d) List is outlined in the Listing Methodology document.
What are the integrated report categories?
The primary purpose of this Integrated Report is to provide information on the water quality status of all surface waters within the state of Colorado. To do this, the division places each waterbody in one of the reporting categories or subcategories based on what is known about its water quality, and the analysis of whether the data demonstrates that the designated use is supported.
The categories represent varying levels of attainment, ranging from Category 1, where the waterbody is attaining water quality standards, to Category 5, where the waterbody is not meeting water quality standards, and a TMDL is needed. A description of Colorado's categories and subcategories is presented in the figure.
During the assessment process, these categories are first applied to individual pollutants and classified uses for each waterbody. This can result in multiple categories within a single waterbody. In these cases, a rating system is used to apply a single category to a waterbody. Typically, the overall highest category for all the classified uses is assigned to the waterbody.
Background Information
In Colorado, there are over 90,000 miles of rivers and more than 270,000 acres of lakes. The majority of rivers originate in the pristine, high alpine, environment of the Rocky Mountains and water flows downstream through the high desert or high plains regions before leaving the state.
Nearly half of the state is flat. The Colorado High Plains, which are part of the Great Plains, lie east of the southern Rocky Mountains. They are sparsely populated, with most people living along the South Platte and Arkansas Rivers.
Numerous dams and reclamation projects on these rivers supply hydroelectric power, and provide water for irrigation and municipal and industrial use. The Colorado-Big Thompson and the Fryingpan-Arkansas projects are two of the largest. They divert water from the Western Slope, which has 80 percent of the state’s surface water, to the Eastern Slope, where most of the population and farmland is concentrated.
How are Colorado's waters subdivided?
Colorado's surface waters are divided into seven regulatory basins (major river basins): Arkansas, Upper Colorado and North Platte, San Juan and Dolores, Gunnison and Lower Dolores, Rio Grande, Lower Colorado, and South Platte. Each regulatory basin is further divided into subbasins (minor river basins).
Waterbodies within a subbasin are further divided into specific water segments. Segments may include a specified stretch of a river, a tributary, a lake or reservoir, or a group of waters within the basin.
During the water quality assessment process, segments may be divided into assessment units, which are unique portions of the waterbody with no spatial overlap.
Waterbody IDs and assessment unit IDs
The waterbody ID (WBID) identifies segments as they are defined in basin Regulations 32-38. A complete list of the regulatory basins and subbasins can be found in this key.
The following example illustrates Colorado's waterbody identification system for a waterbody in the Bear Creek subbasin (COSPBE01a). Continue reading to learn about the letters and numbers that make up the waterbody ID.
1) The four letters at the beginning of each waterbody ID identify the state and the regulatory basin (COSP).
2) The fifth and sixth letters of each waterbody ID identify the subbasin (COSPBE).
3) The final two or three characters of each waterbody ID correspond to a description of the specific state waters included within the segment (COSPBE01a).
4) The underscore and letter at the end of the waterbody ID correspond to the assessment unit ID (COSPBE01a_B).
Colorado reports on water quality in the state by assessment unit IDs (AUID). The AUID describes the spatial extent and the attainment status of each portion of a waterbody.
Assessment Results
The division assesses water quality across the state in five-year cycles, focusing on a section of the state each year. In every fifth year, the division focuses assessments on outstanding issues statewide that stakeholders would like to revisit. Surface water quality assessment efforts during the reporting period of 2020 and 2021 focused on the San Juan and Dolores River Basins (Regulation 34), the Gunnison and Lower Dolores River Basins (Regulation 35), and where outstanding issues were identified statewide.
The following section summarizes the status of water quality in Colorado. This characterization of water quality is the result of the ongoing assessment of all readily available and existing data collected from government, municipal, and private entities working throughout Colorado. A total of 85,355 river miles and 186,733 lake acres have been assessed.
Summary of reporting categories
Based on water quality assessments, Colorado reports the water quality standard attainment status of all state waterbodies to the EPA. Each waterbody is placed in one of the unique assessment categories. All reporting categories for rivers and lakes are summarized in the tables below.
Category summary for Colorado's rivers and streams
Category summary for Colorado's lakes and Reservoirs
Summary of classified uses for rivers and streams
Colorado has adopted five categories of classified uses; aquatic life, recreation, water supply, agriculture, and wetlands. Colorado's use classifications are described in Regulation 31 section 31.13(1).
Each classified use of a waterbody is assigned a level of support. Waters fully supporting a classified use are considered to be in category 1, not assessed are in category 3a, insufficient data/information are in category 3b, and waters not supporting a classified use are in categories 4 and 5. The attainment of each classified use for rivers is summarized in the table below.
Attainment of classified uses for rivers and streams. Data is expressed in miles.
Causes of river impairments
In Colorado, when a standard is exceeded, we determine that the associated use is in "non-attainment" status and then determine the cause. For example, if the body of water has a classified use for aquatic life, and the standard for zinc that has been adopted to protect aquatic life for this body of water is exceeded, then the "aquatic life" use would be in "non-attainment" status and the cause would be zinc.
The primary causes of impairments for streams and rivers are summarized in the table below.
Primary causes of impairments for streams and rivers
Clean lakes program
Section 314 of the Clean Water Act requires states to report on the status of publicly owned lakes. Colorado has approximately 1,533 publicly owned lakes of greater than ten surface acres. The total surface acreage of these lakes has been estimated at 249,787. Publicly owned lakes are defined as those natural lakes, reservoirs, or ponds where the public has access to recreational activities such as fishing and swimming or where the classified uses such as water supply affect the public.
Each summer, up to 10 lakes are chosen from the basin of focus to monitor (three times each) from July through September. The lake and reservoir monitoring efforts provide data to evaluate the trophic status and to assess the attainment of water quality standards. As part of the lake assessments, the division also considers data collected by agencies other than the division.
Summary of Classified uses for lakes and reservoirs
The primary purpose for monitoring lakes in Colorado is to assess if lakes are in attainment of their classified uses by comparing water quality measurements against applicable lake standards. The attainment of each classified use for lakes is summarized in the table below.
Waters fully supporting a classified use are considered to be in category 1, not assessed are in category 3a, insufficient data/information are in category 3b, and waters not supporting a classified use are in categories 4 and 5.
Attainment of classified uses for lakes and reservoirs. Data is expressed in acres.
Causes of lake impairments
For lakes, the most common causes contributing to non-attainment of uses in terms of acres are arsenic, selenium, and temperature. The primary causes of impairments for lakes and reservoirs are summarized in the table below.
Primary causes of impairments for lakes and reservoirs
Fish consumption advisories
The fish consumption advisory program is overseen by a technical advisory committee made up of staff from the division, the Division of Environmental Health and Sustainability, and the Division of Parks and Wildlife. Committee members work together to develop sampling plans, analyze fish data, and communicate advisories. Colorado Parks and Wildlife biologists collect fish throughout the state, and the Colorado State Public Health Laboratory conducts the chemical analysis. Data collected through the fish consumption program, as well as data collected by other agencies within the state, is used to inform both attainment assessment and the state’s fish consumption advisory program.
Site-specific fish consumption advisories are currently issued for fish species in waterbodies where the weighted mean mercury of at least 10 samples is greater than or equal to 0.3 mg/kg. Some advisories were issued using previously employed methodologies. Advisories are retained until sufficient data can be assessed using the current methodology. The division has 28 active advisories based on this approach (approximately 28 percent of the tested waterbodies).
To learn more about fish consumption advisories in Colorado:
- Fish consumption dashboard - Provides active fish consumption advisories, state guidelines, and fish sampling results.
- Fish consumption web page - Provides general information on Colorado's fish consumption advisory program, mercury bioaccumulation, assessment methodologies, and materials related to contaminants in fish and consumption advisories.
Harmful algae blooms
Cyanobacteria harmful algae blooms (cyanoHABs) have been detected in Colorado waterbodies since at least 2001 and can have negative impacts on public and environmental health. These organisms can sometimes produce toxins that affect humans and animals. In addition to toxic effects, algae blooms can have detrimental ecological and economic effects. For example, fish kills may result from reduced dissolved oxygen in the water, and economic impacts occur when blooms affect recreational industries such as fisheries and tourism.
The division collects baseline cyanotoxin samples at routine lake sites and emergency samples at reported algae bloom sites. The division partners to obtain emergency samples at sites managed by Colorado Parks and Wildlife.
To learn more about harmful algae blooms in Colorado:
- Toxic algae web page - Provides general information, fact sheets, an updated toolkit for recreational waterbody managers, and caution/warning signs for waterbody managers to use.
- Toxic algae dashboard - Provides historical algal toxin test results for some waterbodies. These data do not represent all recreational bodies of water in Colorado and do not represent current conditions.
How to learn more about your watershed
How's My Waterway is an EPA tool that helps users find information on the condition of their local waters based on data provided by states, federal, tribal, local agencies, and others. The tool provides the public with water quality information on a community, state, or national scale.
To learn more about the water quality in your local watershed, visit How's My Waterway .
Water Quality Programs
The management of Colorado’s water quality is crucial to the continued development of the state and to the quality of life the state offers to its citizens. The division plays an important role in the protection and restoration of the state’s streams, lakes and reservoirs and in assuring that the citizens of Colorado have safe water to drink. A summary of the water quality programs is included below.
Water quality monitoring
Monitoring of water quality is an important component of the state's water quality program. Monitoring and data analysis are essential for reviewing and developing standards for triennial water quality standards reviews, water quality assessments, developing TMDLs, Clean Water Act Section 303(d) listing determinations, and reporting trends and water quality status in the 305(b) report. The division’s surface water monitoring activities are grouped into four general types: (1) routine sampling, (2) special studies, (3) aquatic life and habitat studies, and (4) lakes and reservoir monitoring.
- Routine sampling: Routine sampling is the collection of water quality samples at a network of fixed sites on a regular schedule, such as monthly or bimonthly. These sites are sampled for multiple purposes, including reviewing and developing water quality standards for rulemaking hearings, water quality assessments, trend detection, and TMDL development. The division's routine water quality samples are collected by three technicians stationed in Denver. Samples are analyzed by the Colorado State Public Health Laboratory.
- Special studies: The division conducts a variety of special studies and monitoring efforts. Special studies include macroinvertebrate studies, fish tissue studies, temperature monitoring, selenium speciation and arsenic studies, studies to support TMDL development, and studies to evaluate nonpoint source project work.
- Aquatic life and habitat studies: The division conducts biological and habitat monitoring to obtain data for use in stream standards and classification reviews and for determining attainment of the aquatic life use in the context of the listing of impaired waters pursuant to Section 303(d) of the Clean Water Act. This monitoring typically includes macroinvertebrate sampling, attached algae analysis, chemical sampling, and habitat evaluation.
- Lakes and reservoir monitoring: The division conducts monitoring at a limited number of reservoirs and lakes around the state to determine their trophic status, develop TMDLs, and support changes to standards and classifications during triennial reviews. Resources for lake monitoring are limited, as funds for such monitoring originate from the overall surface water monitoring program. In 2019, additional resources were added to the lakes monitoring efforts to focus on harmful algal blooms. The division assists agencies and local waterbody managers with their response to concerns associated with harmful algal blooms.
For more information on surface water monitoring, visit the Rivers, Lakes, and Streams web page .
Water quality standards
Water quality standards are established by the commission and applied to state surface waters to protect the beneficial uses. These standards are the regulatory basis for limits placed on discharges as well as the thresholds used to assess the condition of waterbodies. A discussion of the water quality standards program can be found in Part II of the Water Quality Control Commission Policy 98-2: A Guide to Colorado Water Programs for Water Quality Management and Drinking Water .
10-year water quality roadmap
The division has developed a 10-year water quality roadmap and is committed to ensuring that appropriate and protective criteria are applied to protect the beneficial uses of water in Colorado. Prior to 2027, the division will work to refine and develop standards for ammonia, arsenic, cadmium, selenium, total nitrogen, total phosphorus, and temperature while at the same time developing feasibility information to assist dischargers with proposing discharger-specific variances, site-specific standards, and achieving compliance with their permits. The division worked with a technical advisory committee to consider revised criteria for cadmium, which resulted in the adoption of statewide cadmium standards revisions in December 2019. For more information on the 10-year roadmap, visit the Water Quality 10-year Roadmap web page .
Total Maximum Daily Loads (TMDLs)
When waterbodies are not attaining water quality standards, a pollutant budget is developed. The purpose of this budget is to identify what, if anything, needs to happen to control sources of the pollutant that is impacting water quality. These pollutant budgets are the basis for Total Maximum Daily Load (TMDL) Reports and Alternative Restoration Plans.
A TMDL is a technical analysis designed to answer the following questions about a waterbody that is not meeting water quality standards (i.e., an impaired waterbody):
- What is the source(s) of pollution causing the waterbody to exceed standards?
- How much of the pollution is coming from natural/background sources?
- How much of the pollution is coming from point source discharges (e.g. treatment plants, industry, discharging mines, urban stormwater)?
- How much of the pollution is coming from agricultural runoff and other nonpoint sources of pollution?
- How much pollution would need to be reduced from each source in order for the waterbody to attain standards?
An Alternative Restoration Plan is a near-term plan or description of actions with a schedule and milestones that is more immediately beneficial or practicable for achieving water quality standards rather than developing a TMDL. An Alternative Restoration Plan may be appropriate when there are unique local circumstances such as the presence of a watershed group or other parties with available funding opportunities to address the cause of impairment in the near term. An Alternative Restoration Plan may also be appropriate if an initial review determines that particular point or nonpoint sources are responsible for the impairment and there are clear mechanisms to address these sources. If water quality standards are not attained after implementing an Alternative Restoration Plan, a TMDL is necessary.
The development of TMDLs and Alternative Restoration Plans is a focus for the division’s Watershed Analysis and Implementation Support workgroup. The workgroup collaborates with many stakeholders as these technical analyses are produced. This collaboration is particularly important because many people have data and other information that are critical for the development of pollutant budgets. For more information about how you can become involved and provide input, visit the Total Maximum Daily Loads (TMDLs) web page .
Nonpoint source
Unlike pollution from industrial and sewage treatment plants and other regulated discharges, nonpoint source pollution comes from many sources spread out over large areas and is caused by runoff resulting from rainfall or snowmelt. As the runoff moves over and through the ground, it picks up, carries away, and deposits natural and human-made pollutants in lakes, rivers, wetlands, and groundwater. Basic changes to common, everyday practices can play an important role in controlling nonpoint source pollution from urbanization, agricultural and forestry activities, and many other actions across the landscape that can ultimately lead to water quality impacts. The division’s nonpoint source program is here to help partners in watersheds across the state reduce nonpoint source pollution. For more information about how you can become involved, visit the Nonpoint Source Pollution Management web page .
Clean water permitting
The Clean Water Act prohibits the discharge of pollutants from a point source to surface water without a permit. The National Pollutant Discharge Elimination System permit program was established by the Clean Water Act to regulate such discharges. Because the state has developed a program that meets the requirements of the Clean Water Act, the primary discharge permit program in Colorado is administered by the division rather than EPA (subject to EPA review and oversight).
Permits establish pollutant levels that can be discharged to surface water and groundwater in a manner that is protective of public health and the environment. Permits also establish details about discharge monitoring and recordkeeping and include instructions on when notification to the state is required. For more information on permits, visit the Clean Water Permits web page .
Public Participation
Colorado has an extensive public participation process associated with the development of the Integrated Report that is informative and open. In addition to the public processes in place for updating the 303(d) Listing Methodology and the 303(d) List of Impaired Waters, a process is also in place for revising the 305(b) portion of the Integrated Report. A summary of all of these public processes is included below.
303(d) Listing Methodology
The 2022 Section 303(d) Listing Methodology was available for public comment in April 2020 and then approved by the commission at the public administrative action hearing on May 11, 2020. The commission considered all public comments received and encouraged public participation at the administrative action hearing.
Water quality data call
The division solicited water quality data from June 15, 2020, to September 15, 2020. The period of record for data collected in the basin of focus (San Juan and Dolores River Basins (Regulation 34), and the Gunnison and Lower Dolores River Basins (Regulation 35)) was from January 1, 2015 to December 31, 2019. Additional water quality data was also submitted where there were outstanding issues statewide.
303(d) List of Impaired Waters
The division encouraged public participation during the rulemaking process for the adoption of the 2022 Section 303(d) List of Impaired Waters (Regulation 93). The public was formally notified of a 28-day public comment period from February 25, 2021, to March 24, 2021. The commission considered all public comments and adopted the 2022 Section 303(d) List of Impaired Waters (Regulation 93) at the May 10, 2021, public rulemaking hearing.
305(b) portion of Integrated Report
The division provided a 29-day public comment period for the draft 305(b) portion of the 2022 Integrated Report. The draft 305(b) report was available for public comment on the commission’s website from September 1, 2021, to September 29, 2021, and then approved by the commission at a public administrative action hearing on October 12, 2021.
How to get involved
If you would like to be involved in future 303(d) Listing Methodology workgroups to review and update the document, visit the division's 303(d) Listing Methodology Engagement web page .
If you have data that you would like to submit for future water quality data calls, visit the division's Rivers, Lakes, and Streams Data web page for data submission templates, instructions, and other information.
If you would like to participate in the 2024 303(d) List of Impaired Waters (Regulation 93) process - sign up to receive the commission hearing notices .
If you would like to learn more about engagement opportunities with the division, visit the Water Quality Engagement web page .
Resources
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References
U.S. Environmental Protection Agency. Integrated Reporting Guidance under CWA Sections 303(d), 305(b) and 314. https://www.epa.gov/tmdl/integrated-reporting-guidance-under-cwa-sections-303d-305b-and-314 .
U.S. Environmental Protection Agency. Overview of Identifying and Restoring Impaired Waters under Section 303(d) of the CWA. Overview of Identifying and Restoring Impaired Waters under Section 303(d) of the CWA | US EPA .
