Colorado Water Resources Circular No. 20

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• Colorado has felt a particular need to strengthen its water poli- cies. Interstate compacts have placed demanding requirements on the water crossing Colorado's boundaries. The development of irrigation and growth of metropolitan areas east of the Continental Divide have further complicated Colorado's water problems. In an attempt to solve some of these problems, many water projects have been constructed in Colorado to provide storage for better distri- bution -of -the- annual water supply: Some- projects also enhance the supply within a watershed with the transbasin or transmountain diversion of water. The Fryingpan- Arkansas Project will bring water from head- water tributaries of the Fryingpan River in the Upper Colorado River Basin into tributaries of the Arkansas River. This water will be stored in nearby reservoirs, used for hydroelectric power generation, and then transported more than 170 miles in the Arkansas River to fulfill irri- gation and municipal needs downstream. The design and operation of such water development plans greatly influence the economic and hydrologic success of the project. Purpose and Scope In July of 1970, the U.S. Geological Survey, in cooperation with the Colorado Division of Water Resources, Office of the State Engineer, and.the Southeastern Colorado Water Conservancy District, began a study to determine transportation losses along the Arkansas River resulting from deliveries of stored water to downstream water users, and to deter- mine time of travel of reservoir releases from the reservoir to the point of delivery. This report summarizes the results of that study. The study concentrated on a 175 -mile reach of the upper Arkansas River valley from Twin Lakes Reservoir near Granite, Colo., to the Colorado Canal headgate near.Avondale, Colo. (fig. 1). The study con- sisted of analyzing historical records of reservoir releases, Arkansas River streamflow, and ditch diversions; of making detailed measurements of streamflow and water -table changes before and during reservoir re- leases; and of gathering weather and river -water temperature data. Previous Investigations Shortly after completion of the Twin Lakes Tunnel project in the early 1930's, several studies were made by State Engineer M. C. Hinder - lider (Colorado State Plan. Comm. and others, 1939) to determine trans- portation losses of reservoir releases down the Arkansas River. As the result of these studies, a policy was adopted charging releases a loss of 0.07 percent per mile of river. For example, if the release is 100 ft /s (cubic feet per second), the loss along the 175 miles of river between Twin Lakes and the Colorado Canal headgate would be 12.2 ft /s. • 2