Safe, clean water is important to all Coloradans, whether it’s drinking water for humans and animals, cooking, irrigation, recreation, or for fish and wildlife. Water quality plays a critical role in Colorado given our agricultural heritage and economy, our robust recreation and tourism industry, and limited and valued natural resources. As a headwaters state, we are responsible for finding the appropriate balance between protecting our water resources and expensive financial and regulatory commitments necessary to ensure quality water for Coloradans and our downstream neighbors.

Major Factors Affecting Water Quality
Natural FactorsGeology- Formations with varying amounts of minerals or metals
- Different soil types
- Formations containing naturally occurring radionuclides, such as radon and uranium
Climate- Mountainous areas with considerable snowmelt runoff vs. arid areas with minimal runoff
- Cooler vs. warmer in-stream temperatures
Vegetation- Dense or sparse vegetation of varying types
Wildlife- Fecal bacteria
Wildfires- Erosion
- Sedimentation and ash from burned areas
- Loss of riparian habitat, raising in-stream temperatures
Human-Induced FactorsPoint Source Pollutants- Industrial and municipal wastewater discharges
- Stormwater runoff
- Leaking underground storage tanks
Nonpoint Source Pollutants- Polluted runoff of leaching from areas disturbed by human activity
Structural Changes- Modified stream channels
- Reservoir storage
- Diversion of water from streams
- Drainage of wetlands
Atmospheric Sources- Fuel combustion produces pollutants, such as nitrates that may infiltrate lakes and streams
Source: Table recreated from Water Education Colorado's [WEC] Citizen's Guide to Colorado Water Quality Protection (2013).

Water Quality Legislation

Clean Water Act
Created in 1948, the Federal Water Pollution Control Act was one of the first major pieces of legislation to address water pollution in the US. Growing public awareness and concerns around water pollution led to a variety amendments in 1972, after which the law became commonly known as the Clean Water Act (CWA). These amendments included (US EPA, 2017a):

  • The establishment of the regulatory structure for pollutant discharges into US waters;
  • EPA authority to implement pollution control programs for industry;
  • The criminalization of point source pollution into navigable waters (unless otherwise allowed by an obtained permit);
  • Funding for the construction of sewage treatment plants; and
  • Recognition of the need for planning to mitigate nonpoint source pollution and related problems.

The objective of the CWA is to restore and maintain the chemical, physical, and biological integrity of waters in the US by preventing point and nonpoint pollution sources of pollution.  In addition to funding publicly-owned treatment, the act also serves to maintain the integrity of wetlands. It is one of the United States’ first and most influential modern environmental laws. The EPA coordinates with state governments to fulfill these activities (Copeland, 2016; US EPA, 2017a).

Water Quality Act of 1987
Revisions in 1981 streamlined the funding process for treatment plant construction, enhancing the capabilities of those built under the program. Further amendments made in 1987—known as the Water Quality Act (WQA)—phased out this grants program and replaced it with the State Water Pollution Control Revolving Fund (commonly known as the Clean Water State Revolving Fund), which help to meet water quality needs by building on existing EPA-state partnerships (US EPA, 2017a).

Colorado’s wetlands range from alpine wet meadows to marshes along the Arikaree River. Though they cover less than 3% of the state, wetlands and riparian areas are by far the most ecologically and economically significant ecosystem in the state. Colorado Wetland Information Program (n.d.).

In response to increasing issues around stormwater, the WQA also expanded the definition of wastewater to include industrial stormwater discharges and municipal separate storm sewer systems (also known as MS4s) as point sources, and thus required them to obtain national pollutant discharge elimination system (NPDES) permits (US EPA, 2018b). These permits require regulated municipalities to use best management practices to reduce pollutants to the “maximum extent practicable” (Water Quality Act of 1987, 33 U.S.C. § 1342). Agricultural discharges continued to be exempt, but the WQA created the Nonpoint Source Management Program to provide grants to states, territories and First Nations to support demonstration projects, technology transfer, education, training, technical assistance and related activities designed to reduce nonpoint source water pollution (Water Quality Act of 1987, 33 U.S.C. § 1329).

A wastewater treatment plant in Boulder. City of Boulder (n.d.).

In response to increasing issues around stormwater, the WQA also expanded the definition of wastewater to include industrial stormwater discharges and municipal separate storm sewer systems (also known as MS4s) as point sources, and thus required them to obtain national pollutant discharge elimination system (NPDES) permits (US EPA, 2018b). These permits require regulated municipalities to use best management practices to reduce pollutants to the “maximum extent practicable” (Water Quality Act of 1987, 33 U.S.C. § 1342). Agricultural discharges continued to be exempt, but the WQA created the Nonpoint Source Management Program to provide grants to states, territories and First Nations to support demonstration projects, technology transfer, education, training, technical assistance and related activities designed to reduce nonpoint source water pollution (Water Quality Act of 1987, 33 U.S.C. § 1329).

Additionally, the WQA created a program for the management of biosolids (sludge) generated by publicly-owned treatment works (POTWs). The EPA was required to develop guidelines for usage and disposal of sewage sludge or biosolids, and the agency created an Intra-Agency Sludge Task Force to aid in this task (Water Quality Act of 1987, 33 U.S.C. § 1345).

Safe Drinking Water Act
The Safe Drinking Water Act (SDWA) was enacted in 1974 to protect public drinking water supplies. Under the SDWA, the EPA sets standards for drinking water quality and implements programs to ensure safe drinking water (US EPA, 2017c). The SDWA applies to every public water system in the US—of which there are currently more than 151,000. The Act does not cover private wells (Safe Drinking Water Act of 1974; US EPA, 2017b).

The National Primary Drinking Water Regulations set by the EPA under the SDWA include both mandatory maximum contaminant levels (MCLs) and voluntary maximum contaminant level goals (MCLGs) for contaminants that may cause adverse public health effects. Water standards are organized into six categories: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals, and radionuclides (US EPA, 1988). To meet these requirements, public water systems are required to monitor water for contaminants, and water samples must be regularly analyzed using EPA-approved testing methods. Regulatory oversight of public water systems is managed by “primacy” agencies—either state government agencies, Indian tribes, or EPA regional offices (US EPA, 2018a).

A variety of amendments have expanded upon the original SDWA:

  • 1986: The National Primary Drinking Water Regulations must also be applied to community and non-transient non-community water systems (US EPA, 1986).
  • 1996: Regulatory and protective activities must be communicated via consumer confidence reports and public right-to-know; the EPA must conduct cost-benefit analyses and strength protections against microbial contaminants; water system operators must be EPA-certified; and small water systems must receive special consideration to ensure they have the managerial, financial, and technical ability to comply with drinking water standards (Government Publishing Office [GPO], 1996).
  • 2005: Fluids or other propping agents (except diesel) used for fracking are exempt from underground injection regulations (Energy Policy Act of 2005, 42 U.S.C. § 1421).
  • 2011: Lead in drinking water must be reduced or eliminated via lead-free plumbing fixtures and fittings (Reduction of Lead in Drinking Water Act, 42 U.S.C. § 300).
  • 2015: Risks associated with algal toxins in drinking water must be assessed and managed by the EPA (US EPA, 2015).
  • 2016: Water infrastructure improvements, necessitated by water contamination crises like that in Flint, MI, shall be supported by a loan program, communicated to the public, and mitigated by a voluntary testing program for water supplies in schools (Grassroots Rural and Small Community Water Systems Assistance Act of 2016, 42 U.S.C. § 300).

Water Quality in Colorado

Statewide surface water and groundwater standards are determined by the Water Quality Control Commission, housed under the Colorado State Department of Public Health & Environment. These standards are used to assess the quality of the state’s waters and for establishing regulatory requirements for activities that may impact water quality. A complete list of regulations can be found here. Private water wells are not regulated by the state of Colorado and homeowners are responsible for testing, interpreting results, and correcting problems with their well’s water quality (Colorado Dept. of Public Health and Environment [CDPHE], 2017).

How do I test my water quality?
Homeowners often have questions about where and how to test their water sources. There is no a generic water test for everything, as each contaminant must be evaluated individually. The Colorado Department of Public Health and Environment offers suggestions here, as well as other FAQs here. The Tri-County Health Department provides detailed information on to test your well here.

Experts at Colorado State University have also developed an online assessment tool to interpret the results of your water sample. It is recommended homeowners maintain detailed records of test results in order to track changes in water quality over time.

A variety of tests exist to determine water quality.

Water Pollutants

Water pollutants are broadly defined by federal and Colorado state law as any substance that adversely affects water quality or impairs the anticipated uses of that water. Examples of common water pollutants in Colorado include metals, nutrients such as phosphorus and nitrogen, ammonia, pathogens like disease-causing bacteria, sediment, and salinity. Even heat may be considered a pollutant— as elevated temperatures may harm aquatic life (WEC, 2013).

Metals can be lethal to fish and other aquatic fauna, as well as to humans. Copper, arsenic, cadmium, mercury, zinc, and lead all occur naturally in the rock of Colorado’s mountains; and mining and mineral processing can expose large quantities of them to erosion and runoff, resulting in potential contamination of nearby surface waters. Sulfide minerals exposed by mining can also react with water and oxygen to produce acid, further leaching metals from the rock and increasing their toxicity (CDPHE, n.d.d, n.d.b).

In the Rocky Mountains, acid drainage—which results when water flows through acidic minerals that have been exposed due to mining—is a major water quality problem. Photo of the Gold King Mine Spill. Jerry McBride/The Durango Herald (2015).
Algal blooms are common in Colorado, especially during warmer weather. CDPHE (n.d.f).

Nutrients can lead to or exacerbate algae growth in standing bodies of water—a process called eutrophication, common in Colorado’s urban reservoirs. Excessive algae reduces water clarity, making it less desirable for swimming or boating. Algae blooms can cause taste and odor problems in municipal drinking water supplies. Bacteria may also decompose algae, consuming oxygen in the process and, in turn, lowering dissolved oxygen to levels potentially harmful to fish and other aquatic life (Colorado State University [CSU], n.d.a).

Excessive sediments deposited on stream and lake bottoms can smother or otherwise damage aquatic habitats and spawning areas, reducing species’ survival and growth rates. Sedimentation may also impair food sources, or fill in shallow and slow-water habitats, which provide important cover and refuge for aquatic life. Additionally, it may inundate and harm wetlands (WEC, 2013).

In the Colorado River basin specifically, salinity is the biggest water-quality issue. Major sources include the saline soils of the Colorado Plateau and agricultural irrigation-return flows. Salinity concentrations in the headwaters are generally less than 50 milligrams per liter, but increase to approximately 900 milligrams per liter at the international boundary with Mexico. Urbanization, population growth, mining, agricultural practices, and recreation also all affect salinity concentrations in the Colorado River (US Geological Survey [USGS], 2000).

In Colorado, river modifications like dams and diversions affect water quality, particularly in the Colorado River system. Reservoirs may harbor chemicals in their sediments or water that can be retained for years, while dams may reduce necessary sediment and alter physical properties such as flow and temperature. Activities and developments such as road construction and maintenance, logging, grazing, mountain towns, off-road vehicle use, and ski areas can all also produce pollutants that may impact water quality (USGS, 2000; WEC, 2013).

Roads in particular may increase erosion, in-stream debris, and sedimentation. Road construction that narrows or straightens a stream channel increases the risk of erosion and may reduce or eliminate a diversity of habitats necessary to a healthy stream ecosystem. Highways open year-round through Colorado’s mountains require large quantities of road traction sand to mitigate winter driving conditions, which may then run off and cause excessive sedimentation in nearby waterways. Silt fences, adequate setbacks, drainage filters, and sufficient design for maximum runoff have all proven successful in alleviating many of the pollutants and negative water quality impacts that stem from roadwork (US EPA, 1995).

Outfall of the Bousted Tunnel delivers water from Roaring Fork and Fryingpan rivers to East Slope. Brent Gardner-Smith/Aspen Journalism (2015).
Urban sewage can negatively impact water quality.

Urban and suburban development—on the rise due to Colorado’s explosive population growth—also produces pollutants that have potentially significant water quality impacts. High concentrations of people means larger quantities of human sewage that must be treated and disposed. Domestic wastewater typically receives substantial treatment before it is discharged into Colorado streams, but those discharges nonetheless have the potential to increase concentrations of ammonia, nutrients, and pathogens and to reduce oxygen levels in the receiving water source. Motor oil, grease, and other materials from automobile operation and maintenance are deposited on driveways, streets, and parking lots in cities and town across the state, while excess fertilizer can runoff from lawns. These areas also have a variety of impervious surfaces such as roofs, streets, and parking lots. During rainfall or snowmelt, pollutants deposited on these surfaces are easily carried into streams, lakes, and reservoirs (Liyanage & Yamada, 2017; WEC, 2013).

In more rural areas of Colorado, agricultural production—and its sometimes excessive applications of pesticides and fertilizers, in particular—can leach through the soil to contaminate underlying groundwater or may run off the surface and enter streams or lakes. In certain parts of the state, some soils naturally contain potentially polluting substances, such as selenium, and irrigation and livestock grazing activities may accelerate leaching of these materials into surface and ground waters. Concentrated animal feeding operations (CAFOs) may also pollute Colorado water if the large quantities of animal manure generated by these facilities are not properly managed. There are approximately 400 CAFOs in the state, the majority of which operate on the eastern plains (CSU, n.d.a, n.d.b; WEC, 2013).

Colorado’s oil and gas production activities also present opportunities for water pollution. Colorado has approximately 47,000 producing oil and gas wells in 45 of its counties; Weld County alone has more than 17,800 active wells (WEC, 2013). If not properly constructed, these wells may allow for cross-contamination of pollutants from hydrocarbon-bearing zones into fresh groundwater zones. When wells are pumped, most bring up groundwater. This “produced water” often has high salinity levels and is typically re-injected deep underground, where it may enter the groundwater supply if not handled properly. Accidental spillage is also a risk; in such cases, oil, gas, or produced water may contaminate surface or groundwater (Colorado Water and Energy Research Center [CWERC], 2014).

Cattle at 5 Star Feedlot outside of Bethune CO. CAFOs like this are common in eastern Colorado. Sam Brasch/CPR News (2017).

Point Source Pollution
Point source pollutants are contaminated discharges that enter a body of water from “any discernible, confined, and discrete conveyance;” they may also be called “end-of-pipe” discharges. Common point source pollutants include industrial and municipal wastewater discharges and stormwater runoff. If the pollutant is under someone’s direct control, then released into to a water body, it is generally considered to be point source. However, under Colorado law, agricultural stormwater runoff, irrigation return flows, and certain water management activities associated with the storage or delivery of water are exempted from regulation as point source discharges. The largest continuous point source pollutants in Colorado are from municipal sewage and industrial wastewater treatment plants (CSU, n.d.b; WEC, 2013).

Nonpoint Source Pollution
Water runoff from impervious surfaces such as roads and parking lots carries contaminants to nearby waterways. In addition, over application of contaminants such as lawn fertilizer can contribute to water contamination. A nonpoint source pollutant is diffuse: rather than coming from a fixed location, it comes from multiple, dispersed sources. Any pollutant that does not meet the definition of point source is considered nonpoint source. Nonpoint source pollution is caused by irrigation, rainfall, or snowmelt moving over and through the ground; picking up carrying natural and human-made pollutants; and finally depositing them into lakes, rivers, wetlands and groundwater. Common nonpoint pollutants include runoff or leaching from agricultural lands, inactive mine sites, construction sites, and urban development. In particular, mining in the late 19th century and first half of the 20th century still today has substantial and ongoing impacts on water in Colorado’s major river basins. Of an estimated 23,000 abandoned mines in Colorado, several hundred continue to adversely affect the state’s water supplies. This and other nonpoint sources of pollution are the largest sources driving Colorado water quality problems (CDPHE, n.d.c).

Nonpoint source water pollution from roads. NOAA (2017).

Water Quality Monitoring and Assessment

Preventing water contamination is much less expensive then attempting to clean up contaminates after the fact. It is extremely expensive and difficult to ensure adequate clean water after a contamination episode. Colorado’s Water Quality Control Division uses a variety of monitoring techniques to evaluate water health of streams, lakes and reservoirs. Chemical monitoring strategies sample chemical constituents such as ammonia, copper, or bacteria in surface water. Biological monitoring assesses fish populations, aquatic insects, algae, and aquatic habitat. Temperature monitoring of surface waters helps to determine ambient water quality and health; informs the development and revision of water quality standards; and is used to identify trends and determine whether water quality standards are being met (CDPHE, n.d.e). Routine water quality monitoring is conducted at approximately 75 permanent sites throughout the state, with monthly samples collected to measure levels of metals, nutrients, and other water quality parameters. Additional monitoring is periodically conducted at 150 or so additional sites; such assessment may precede a regular review of a basin’s water quality, for example. Once every two years, the Division compiles all water quality monitoring information received (whether collected by the Division or others) into a Status of Water Quality in Colorado report (CDPHE, n.d.a); WEC, 2013).

The humpback chub is one of only a handful of species that have evolved to withstand the Colorado River's turbulent whitewater canyons, and all but disappeared as large dams began controlling flows and changing water temperature. As such, they are one of many species monitored as an indicator of water quality in Colorado. USFWS (2018).

In addition to state-funded monitoring, permitted point source dischargers must routinely monitor their own discharges and the effects on the receiving bodies of water. Results are reported to the Water Quality Control Division, and this data is used to determine if dischargers are in compliance with permit requirements or if legal action is needed to ensure compliance. In order to determine if nonpoint source control projects in Colorado—which are often funded by federal grants—are in fact improving water quality, monitoring and other project evaluation is also required (WEC, 2013).

Federal agencies such as the U.S. Geological Survey conduct water monitoring efforts in Colorado as part of national research projects, collecting and analyzing the chemical, physical, and biological properties of water, sediment and tissue samples from across the state. The National Water Quality Assessment (NAWQA) program, for example, monitors long-term changes in water quality in major river basins and aquifers across the country, including the Colorado, Big Thompson, and South Platte rivers and the High Plains, San Luis Valley, and Leadville Limestone aquifer systems in Colorado (USGS, n.d.a).

Groups and organizations other than state and federal agencies also conduct water quality monitoring in Colorado, including universities, watershed groups, municipalities, and private industry. Once deemed to be well-documented and reliable, monitoring data provided by these external bodies to the Division can be used to help determine water quality and standards and to identify impaired waters. If any of these monitoring efforts reveal a lake, reservoir or stream segment is not meeting water quality standards, the Division targets it for further review and action (WEC, 2013).

The Measurable Results Program (MRP) is one example of a water monitoring effort in Colorado, which began in 2010 when the Colorado Watershed Assembly partnered with the Water Quality Control Division’s Nonpoint Source Program to monitor restoration projects that were previously funded by the National Park Service. The MRP assists local watershed groups by providing documentation of restoration results and helping to enhance the quality and quantity of monitoring data (Colorado Watershed Assembly, n.d.).

Since 1989, the Colorado River Watch Program has been working with volunteers to monitor Colorado’s waters. Interested citizens, teachers, and students are outfitted with the equipment, supplies, and training to conduct EPA- and state-approved water quality monitoring activities—the data from which provides reliable scientific support for the decision-making processes of the Colorado Water Quality Control Commission. Not only does the program deliver water monitoring data, but it also fosters environmental stewardship in all of its volunteers (Colorado Watershed Assembly, n.d.).

Pollution Controls
Colorado uses four primary mechanisms to control water pollution: discharge permits, control regulations, voluntary controls, and grants to organizations that help improve water quality.

Discharge permits
Permits for point source discharges regulate municipal and industrial wastewater and stormwater discharges in Colorado by placing limits on the amount of pollutants dischargers may release into Colorado’s waters. These permits are required by the Clean Water Act National Pollution Discharge Elimination System (NPDES), and are issued by the state’s Water Quality Control Division. The EPA issues permits as well, for discharges from federal facilities and on American Indian reservations. It also has the power to veto any individual permit and to enforce state-issued permits. All dischargers in Colorado must renew their permits every five years (CDPHE, 2017; WEC, 2013).

Municipal and industrial wastewater treatment plants are primarily required to implement effluent limits, either technology-based and water quality-based. Technology-based limits require the discharger to attain a minimum level of pollution control determined by the EPA to be technologically achievable. Water quality-based limits require the discharger to treat effluent to the extent that the receiving stream will still meet water quality standards, even during low flow conditions. Because so many of Colorado’s streams provide little or no dilution flows at certain times of year, water quality-based effluent limits often are more stringent than technology-based limits (CDPHE, 2017; WEC, 2013).

Point source discharges of stormwater runoff are subject to a separate set of permit requirements than municipal and industrial wastewater discharges, largely due to the different nature of this discharge: rainfall or snowmelt runs over the land surface, carrying pollutants such as pet waste, excess lawn fertilizer, motor oil, cigarette butts, and trash. Rather than a continuous discharging with a relatively consistent volume, stormwater runoff can be highly erratic. As a result, pollution management for stormwater focus primarily on control and minimization of the sources, rather than on treatment prior to discharge (CDPHE, n.d.c); WEC, 2013).

Control regulations
“Control regulation” is a general term for any regulation, excluding discharge permits, determined necessary by Colorado’s Water Quality Control Commission to protect water quality in specific bodies of water or to regulate specific activities. In the first category, Dillon, Cherry Creek, and Chatfield reservoirs, Bear Creek Watershed, and Cheraw Lake are subject to control regulations. The primary activities subject to control regulations, on the other hand, are discharge to municipal sewers, biosolids application, wastewater reuse, and mine drainage (CDPHE, n.d.a; WEC, 2013).

Discharge to municipal sewers is regulated through industrial pretreatment. The primary focus of pretreatment is to ensure discharges do not (1) interfere with subsequent treatments the municipal wastewater treatment plant, (2) pass through the municipal plant untreated, or (3) contaminate the biosolids material removed from the wastewater by municipal treatment. Nearly 30 Colorado municipalities have developed their own pretreatment programs (CDPHE, 2017; WEC, 2013).

Biosolids—semi-solid, organic materials leftover from the treatment of sewage by municipal wastewater treatment plants—are often applied to agricultural lands in Colorado as fertilizer; up to 80 percent of the material generated by these treatment plants will be used as such. Accordingly, regulatory management of biosolids application has been designed to protect surface water from harmful levels of pollutants such as metals or pathogens that may be in found in the biosolids. Some regulations, for instance,  require application rates be based on the nutrient requirements of the crops fertilized with biosolid material; such an approach ensures any potential pollutants are beneficially used, rather than washed away, contaminating ground or surface water (CDPHE, n.d.c; WEC, 2013).

Wastewater reuse, which helps conserve Colorado’s scarce water resources and has been adopted by a number of municipalities for landscape irrigation, is regulated by Water Quality Control Commission. These controls serve to protect public health, but still encourage the use of reclaimed domestic wastewater (CDPHE, n.d.c; WEC, 2013).

Voluntary controls
In Colorado, nonpoint source pollution controls are non-regulatory and adopted on a voluntary basis; such controls aim to prevent pollution from occurring at the source, rather than treating water after contamination has already occurred. The state’s nonpoint source control program primarily uses federal grants as provided for by the Clean Water Act to support voluntary pollution reduction projects. Recently, the program’s focus has narrowed, honing in on projects that clean up polluted and high-priority waters (CDPHE, n.d.a); WEC, 2013).

Colorado Geological Survey Water Quality web page
Web page containing general information on water quality in Colorado, with links to documents relating to their current water quality projects.

Colorado Water Quality Control Division
This website contains an array of water quality information specific to Colorado, including permits, public notices, drinking water information, emergency response and spill notifications, regulations, contacts, etc.

EPA Water Quality Standards Regulations: Colorado
This website presents water quality standards in effect for Clean Water Act (CWA) purposes for Colorado.

National Water Information System: USGS Water-Quality Data for Colorado
The U.S. Geological Survey’s (USGS) National Water Information System (NWIS) is a comprehensive and distributed application that supports the acquisition, processing, and long-term storage of water data. This web page contains water quality data pertaining to Colorado.

Homeowner’s guide to protecting water quality and the environment by Waskom, Bauder & Wardle (2018)
This Colorado State University Extension fact sheet contains information on protecting water quality and the environment around your home.

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Gardner-Smith, B./Aspen Journalism. Outfall of the Bousted Tunnel [IMAGE].

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Grassroots Rural and Small Community Water Systems Assistance Act of 2016, codified as amended as 42 U.S.C. § 300.

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Safe Drinking Water Act of 1974, codified as amended at 42 U.S.C. § 300.

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—–. (2017a). History of the Clean Water Act. Laws & Regulations.

—–. (2017b). Information about Public Water Systems. Drinking Water Requirements for States and Public Water Systems.

—–. (2017c). Safe Drinking Water Act (SDWA).

—–. (2018a). Learn about Drinking Water Analytical Methods. Analytical Methods for Drinking Water.

—–. (2018b). Polluted Runoff: Nonpoint Source (NPS) Pollution.

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—–. (n.d.b). USGS Water-Quality Data for Colorado. National Water Information System: Web Interface.

—–. (2000). Monitoring the Water Quality of the Nation’s Large Rivers: Colorado River NASQAN Program (USGS Fact Sheet FS–014–00). U.S. Department of the Interior.

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US Forest & Wildlife Service [USFWS]. A Humpback Chub [IMAGE].

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Water Quality Act of 1987, codified as amended at 33 U.S.C. § 1329.

Water Quality Act of 1987, codified as amended at 33 U.S.C. § 1342.

Water Quality Act of 1987, codified as amended at 33 U.S.C. § 1345.