Colorado’s water resources supply water not only to the state itself, but also to many surrounding states. With a population that increased from one to five million during the last century, water has been and is the key resource that controls sustainable growth. The CGS plays a leading role in studying how geology and human activities impact Colorado’s important groundwater resources. Colorado is a headwater state, home to the headwaters of four major river systems: the Arkansas, the Colorado, the Platte, and the Rio Grande. However, 80% of the state’s water resources occur in the western part of the state while more than 80% of the population lies in the more arid eastern part of the state, a region that is more dependent on groundwater resources.

Groundwater Resources

An exposure of the Triassic Dolores Formation in a road cut on the east side of the Lemon Reservoir dam on the Florida River in La Plata County, Colorado, May 2019. Beds are dipping south along the Hogback Monocline that separates the San Juan Basin to the south from the San Juan Dome to the north. Here the fluvial sediments consist of interbedded sandstone, siltstone, and mudstone with sandstone dominating. Although not recognized as a major aquifer the sandstone can carry groundwater and at this location water is seeping out through fractures. Photo credit: Peter Barkmann for the CGS.


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SP-52 Messages in Stone cover


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MI-97 LiDAR-Based Map of the Cheraw Fault Scarp. Graphic credit: Colorado Geological Survey

GIS Water Maps

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Stock groundwater well, Lost Creek Basin, Weld and Adams County, Colorado, August 2009. Photo credit: Colorado Geological Survey

ON-010 Colorado Groundwater Atlas

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Abandoned mine structures in the Pike-San Isabel National Forest, Colorado. Photo credit: Colorado Geological Survey

Abandoned Mine Lands

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Pinkerton Hot Springs, La Plata County, Colorado, September 2012. Photo credit Colorado Geological Survey.

Geothermal (Hot Springs)

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As a non-regulatory agency, the CGS conducts scientific studies of the state’s aquifer systems and investigates natural, “background” conditions of water quality, quantity, and movement. We are currently producing comprehensive geology and groundwater studies county-by-county tailored to inform the public, planners, and policy-makers on the intricacies of local geology and groundwater resources. CGS hydrogeologists serve as scientific advisors to Colorado’s nine Basin Roundtables under the InterBasin Compact Committee (IBCC). Our award-winning 2003 Colorado Groundwater Atlas provided a comprehensive look at groundwater and its geological, hydrological, and legal context in the state. A fully updated online Atlas, with an initial deployment in January 2020, is an ongoing project that provides up-to-date information on groundwater resources across the state. The CGS also studies the effects of historic mining on water quality.

Ferrosinter deposits cover the hillside as natural acid rock drainage (ARD) flows into Lower Iron Creek, Alamosa County. Photo credit: CGS.

Surface Geohydrology

The CGS has a long history of research into the effects of geology and human activities on groundwater and surface waters around the state.

Surface Water Quality