Mining pollution fouls the Animas River in August 2015 as a result of the Gold King Mine disaster (photo by Riverhugger via Wikimedia Commons).

Colorado's headwaters regions straddle the Continental Divide and produce clean water that flows into every neighboring state as well as states as far away as California and Mississippi. Growing populations are steadily increasing demand for this vital water resource while climate change threatens its sustainability. At the same time, profit-driven energy and mineral exploitation increases the risk of damaging this natural resource beyond repair.

Historical mining activities have already caused significant damage to the headwaters of every significant river in Colorado, as demonstrated in 2015 by the unintentional release of toxic water from the Gold King Mine into the Animas River. Mines in these regions collect groundwater and expose it to heavy metals and sulfide minerals. Mine dumps and tailings expose sulfide minerals to oxygen. Oxidation displaces the sulfur, which combines with water to form weak sulfuric acid. The acidic water then dissolves minerals from the surrounding rock, often adding significant amounts of dissolved metals to headwaters streams.

Cleanup efforts have improved some streams and rivers, but others remain "virtually devoid of any aquatic life." Of 23,000 abandoned mines in Colorado, 230 are known to be actively contaminating 1,645 miles of Colorado rivers and streams, the equivalent of at least one Gold King disaster every two days – killing fish, harming human health and raising the cost of treating municipal water supplies.

On this page we highlight significant issues in Colorado's headwaters regions, including the headwaters of the Colorado, South Platte, Arkansas and Rio Grande rivers. Ultimately, all of Colorado's Western Slope rivers are tributary to the Colorado River.

Colorado's major river basins (image courtesy of Colorado Division of Water Resources).

(Click here for a more detailed map of Colorado's rivers.)

Colorado River Headwaters

The two principal rivers of the the Southwestern United States and northern Mexico – the Colorado River and the Rio Grande – begin in Colorado. The 1,450-mile-long Colorado River is a vital source of water for 40 million people. The Colorado River's headwaters lie in north-central Colorado, but for all practical purposes, all of Colorado's Western Slope headwaters are Colorado River headwaters.

Historical mining activities have damaged the headwaters ecosystems of the Colorado River and its tributaries, including the Gunnison, San Juan, San Miguel, Animas, Dolores, Yampa and White rivers. Further degrading Western Slope headwaters, trans-mountain water projects have diverted significant portions of these headwaters to Colorado's Front Range where the state's population and industries are concentrated.

Many of these Western Slope river basins are also subject to ongoing coal and oil-and-gas extraction, with the Trump Administration attempting to expand development of these dirty energy resources on public lands in western Colorado. A study by Western Resource Advocates demonstrates that switching to renewable energy sources and more water-efficient thermoelectric power plants could save 160 thousand acre-feet of Colorado River water annually. Continued mineral, coal and oil-an-gas extraction in Colorado River headwaters regions will not only further contaminate this vital water source but continue to waste water through outmoded energy technology.

South Platte River Headwaters

The headwaters of the South Platte River in South Park supply more than 80 percent of the Denver metro area’s drinking water. With more than half of Colorado's 5.5 million residents living in the metro area, the importance of these headwaters cannot be overstated. Aquifers feeding the South Platte and its tributaries flow through geological formations with extensive fractures, and relatively minor disturbances to this geology can cause significant damage to the aquifers and, therefore, to the water supply for more than 3 million people.

Most of these headwaters lands – 354,000 acres – are federally owned. Managed by either the U.S. Forest Service or the U.S. Bureau of Land Management, this critically important area is subject to potential mineral extraction and timber harvesting. The underground "mineral estate," even under much privately owned land, is controlled by the BLM through mineral leases. These leases are auctioned through BLM lease sales, which grant the high bidder the right to extract oil, gas, coal, precious metals and other minerals.

Approximately 36,000 acres in South Park have already been leased for oil-and-gas exploration and production. In addition, the Colorado State Land Board has leased approximately 37,000 acres of the state’s mineral estate in South Park.

Arkansas River Headwaters

The Arkansas River is the most over-appropriated river in the U.S., yet the legacy of mineral extraction has left some headwaters streams “virtually devoid of any aquatic life.” Until the 1980s, toxic mining runoff from abandoned mines near Leadville contaminated the Arkansas River to the extent that brown trout survived for only an average of two years before succumbing to heavy metals poisoning. Less hardy rainbow trout had died off completely.

The turnaround began in the early 1980s, when a federal Superfund designation began the process of cleaning up the mine runoff. Since then, a combination of federal, state, private and nonprofit entities have worked tirelessly to restore the river, which now boasts a 102-mile-long Gold Medal trout fishery.

This decades-long success story on the Arkansas River demonstrates the effectiveness of persistent cleanup and restoration efforts, but significant threats to Arkansas River headwaters remain. In addition to toxins from legacy mining operations, septic systems from increasing development and ecological damage from wildfires and poor land management practices represent persistent threats to water quality.

Rio Grande River Headwaters

With a total length of 1,896 miles, the Rio Grande is the other principal river of the the Southwest and is considered the fourth- or fifth-longest river system in North America, depending on how it is measured. With headwaters in south-central Colorado, it flows through New Mexico before forming part of the international boundary between the United States Mexico. By the time it reaches the Gulf of Mexico, 80 percent of its water has been siphoned off for municipal. agricultural and industrial uses.

Like all headwaters regions in Colorado, Rio Grande headwaters ecosystems have been damaged by mineral extraction. A 2001 study funded by the Colorado Water Conservation Board also identified excessive sedimentation and erosion as significant issues along the Rio Grande. Priorities identified by the study include the need to establish riparian stream buffers to protect headwaters streams and the need to establish cattle exclusion guidelines and target
areas along stream corridors.

The Rio Grande Headwaters Restoration Project is currently leading the Upper Rio Grande Watershed Assessment effort to identify specific causes of significant water degradation and prioritize restoration projects in this headwaters region.