C150172 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I The priority recharge sites were located by balancing a number of issues and factors. Some examples of sites that would be of interest include: (1) a low lying, weedy area that is difficult to farm, (2) a field area of perceived high percolation rates, (3) an area that is not presently farmed for various reasons, (4) a recharge structure close to an existing Union Ditch headgate or an existing Union Ditch lateral, and (5) the proximity of the site to the river. The proposed recharge structures are overlying an alluvial aquifer, which is hydraulically connected to the South Platte River. The movement of ground water into or out of the alluvial aquifer has direct influence on the surface water flow in the South Platte River. These conditions make recharge projects viable for purposes of supplying additional water to the South Platte River. Maps produced by Hurr et al. (1972) describe the hydrogeological characteristics of the aquifer in several reaches of the South Platte River Valley. According to these maps, the aquifer underlying the proposed recharge structures is very amenable to ground water recharge. Aquifer material is primarily gravel and is highly permeable. Highly permeable soil conditions have been verified by observations of longtime agriculturalists. In the vicinity of the Union Ditch, the aquifer saturated thickness ranges from 30 to 80 feet and transmissivities range from 100,000 to 200,000 gallons per day per foot (Hurr et aI., 1972). Several percolation tests for potential recharge ponds have been conducted for the New Cache la Poudre Irrigation Company by Peel (2003), which is also located in Weld County. Peel compares the infiltrate rates found in these percolation tests to the infiltration rates reported by the Weld County Soil Survey (USDA, 1980). Many of Peel's percolation tests were performed on soil textures which are similar to those found at the potential Union Ditch recharge sites. Appendix A includes a summary table of soil infiltration rates for tests conducted by Peel (2003) and includes Weld County Soil Survey maps in the vicinity of the Union Ditch (USDA, 1980). Due to the relatively permeable nature of the soil underlying the proposed recharge structures, it is expected that water diverted into recharge structures will percolate into the aquifer, where ground water will move towards the river. However, it is important to note that pond sites have been identified based on easily observable surface conditions and that percolation tests at the sites are planned or are currently underway. Water Rights The primary source of water for the Union Ditch Company is direct flow water rights out of the South Platte River. In addition, Union also has an absolute storage right in the Union Reservoir and a right to seepage through the Union FDR (feeder) NO.1. The direct flow water rights diverted at the Union Ditch headgate consist of two rights with appropriation dates of 1874 and 1881, totaling 184.03 cfs. State Engineer's records indicate that the historical average annual diversions (1950 through 2002) are 27,067 acre-feet. The Union FDR No. 1 water right has an appropriation date of 1893 for a total decreed amount of 20 cfs. State Engineer's records indicate that the historical average annual seepage to the Union Ditch (1950 through 2002) is 1,860 acre-feet. Union currently owns 5.75 shares of 250 total shares of stock in the Union Reservoir. The Union Reservoir has two absolute storage rights decreed to it with appropriation dates of 1902 and 1973, for a total decreed amount of 19,098 acre-feet. These water rights are summarized in Appendix B. Union Ditch Company Recharge Project Feasibility Study March 2004 Page 8