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

Naturally Degraded Water


Much of the CGS website is under heavy re-construction and will be for some time. The Publications area is working normally, but there is a lot of content from our original site that was in desperate need of updating. Please bear with us as we gather new information and rewrite hundreds of pages of material, gather and properly caption high-resolution images and otherwise bring you some very cool new and archival material never before seen! Stay in touch by subscribing to the >RockTalk< blog where we will announce new items periodically.


Humans are major polluters of the waters of the globe. However, natural groundwater movement also causes significant water contamination globally—including salts, acids, radioactivity, nitrogen, along with metals—arsenic, selenium, zinc, lead, iron and manganese. As we attempt to regulate and clean up human pollution of water, it is important to recognize natural water pollution sources in a particular area. Understanding the geology of an area is important to aid in recognizing potential natural sources of water pollution.

IS-12 Hydrogeologic and Stratigraphic Data Pertinent to Uranium Mining, Cheyenne Basin, Colorado looks at natural groundwater contamination near a proposed in-situ uranium mine in Weld County.

Another related CGS publication is the award-winning study B-54 Natural Acid Rock Drainage Associated with Hydrothermally Altered Terrane in Colorado that reveals the geology behind poor water quality in parts of Colorado. It identifies and examines a number of streams in eleven different head water areas of Colorado where surface water is acidic and has high concentrations of metals upstream of any significant human impacts.