Arkansas River Basin Facts CWCB September 2000

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Endangered Species The native greenback cutthroat trout is the Colorado State Fish. It is federally listed as threatened but has been reintroduced into many streams and lakes. The Arkansas darter is a federal candidate species for listing under the Endangered Species Act and is listed as threatened by the Colorado Division of Wildlife. Unique Characteristics Erosion and channel instability in lower reaches of Fountain Creek. An unusual groundwater mound exists at La Junta and is under investigation, along with substan- tial channel degradation. Development of water supplies will be limited and complex due to the Compact allocation, interstate litigation, and salinity concerns. Litigation with Kansas over compact issues. Groundwater Compact Facts Arkansas River Compact of 1948 The Compact apportions the waters of the Arkansas River between Colorado (60 9/6) and Kansas (40 %) based on the opinion of the U.S. Supreme Court in Colorado v Kansas, 320 U.S. 383 (1943). The Compact established the Arkan- sas River Compact Administration to prescribe procedures for Compact administration, including three representatives from Colorado (a water user from above and below John Martin Reservoir and the Director of the Colorado Water Conservation Board), three Kansas representatives, and a federal representative. The 1980 Operating Principles provide for storage accounts in John Martin Reservoir and the release of water from those accounts for Colorado and Kansas water users. If the conservation pool in die reservoir is depleted, Colorado is required to administer water rights priorities in District 67 (downstream from John Martin). During such periods, Kansas is not entitled to water flowing into the reservoir. Colorado and Kansas have litigated claims concerning Arkansas River water since the early twentieth century. Supreme Court decrees establish principles of equitable apportionment of water between states. In 1995, Colorado was found to have depleted stateline flows in violation of the Compact. The states are now litigating the nature and extent of the injury to Kansas and the method of repayment by Colorado before a Supreme Court appointed Special Master. In response to an order of the Special blaster, the Colorado State Engineer promulgated well administration rules to bring Colorado into compliance with the Compact. Upper Basin - -Above Pueblo Reservoir Alluvium BedrockAquifer Aquifer Stream and glacial Dry Union Formation up Characteristics deposits -- silt to large to 500 ft thick. Fractured boulders granite -- Sawatch and basins within theArkan- Mosquito ranges; sas Basin include the carbonate rock -- Upper Black Squirrel and Leadville Primary Uses Domestic Yield Varies widely due to range of materials: up to 500 gpm at Salida to Buena Vista reach Water Quality Generally potable, a few local exceptions of natural and manmade contamination Source: Colorado Department of Natural Resources Domestic Varies widely: 10 to 200 gpm Lower Basin -- Below Pueblo Reservoir ShaltowAlluvium BedrockAquifer Width varies from 1 to 10 Up to 1,000 ft thick. miles; 30 to 200 ft thick. Sandstone formation in Designated groundwater the Ogallala (Northern basins within theArkan- and Southern High Plains) sas Basin include the The southern part of the Upper Black Squirrel and Denver Basin bedrock Big Sandy. aquifers provides water to Douglas, El Paso and Elbert counties. Agriculture Agriculture, domestic and municipal 10 to 4,000 gpm, 50 to 500 gpm depending on location Generally potable, a few Degrades downstream Generally very good local exceptions of from good in the upper natural and manmade portion of the reach to contamination poor, only marginally useful for irrigation and stockwatering due to salinity