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Surface Water and Groundwater


ater resources consist of surface water and groundwater. Surface water includes lakes, reservoirs, rivers, and streams. Groundwater is located beneath the surface of the earth in aquifers, typically withdrawn through wells. Surface streams in Colorado range from large perennial rivers to small ephemeral tributaries, totaling over 100,000 miles in length. Monitoring of more than 71,000 stream miles in the last five years demonstrates that over 49,000 miles meet or exceed their water quality goals. Surface water supplies the majority of Coloradans with their drinking water, generally through a municipal water system. It also supplies the majority of agricultural irrigation across the state. Surface water is important for drinking, recreation, agricultural and industrial use, as well as the maintenance of aquatic ecosystems. It is the primary focus of Colorado’s water quality management and regulatory system. Groundwater extracted from Colorado’s aquifers provides some 18 percent of the water withdrawn for use in Colorado, primarily for domestic use and agricultural irrigation. Approximately 86 percent of this extracted groundwater is used for agricultural purposes. Groundwater supplies drinking water to roughly 500,000 Coloradans, mostly in small communities and rural areas.

Major Factors Affecting Water Quality

Blake W. Beyea, EscaPhotography

Natural Factors

Human-induced Factors


Formations with varying amounts of minerals or metals Different soil types


Mountainous areas with considerable snowmelt runoff vs. arid areas with minimal runoff Cooler vs. warmer in-stream temperatures


Dense or sparse vegetation of varying types


Fecal bacteria


Erosion Sedimentation and ash from burned areas Loss of riparian habitat, raising in-stream temperatures

Point source pollutants

Industrial and municipal wastewater discharges Stormwater runoff

Nonpoint source pollution

Polluted runoff or leaching from areas disturbed by human activity

Structural changes

Modified stream channels Reservoir storage Diversion of water from streams Drainage of wetlands

A raft sits ready to float on a private pond in San Miguel County.

Citizen’s Guide


C o l o r a d o W at e r Q u a l i t y P r o t e c t i o n

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Citizen's Guide to Colorado Water Quality Protection  
Citizen's Guide to Colorado Water Quality Protection  

Curious as to how the state decides what rivers are healthy for fish, or what lakes are safe for swimming? This desk reference tackles the c...