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<br />Major tributaries to the South Platte include Cheny Creek, Clear Creek, Boulder Creek, the St. Vrain
<br />River, the Big Thompson River, and the Cache la Poudre River, Flows on the river reach their maximum at
<br />Kersey, and although there are no major perennial tributaries downstream of this point, several plains
<br />tributaries contribute significant quantities of water to the South Platte system during periods of high rainfall,
<br />There are approximately 370 reservoirs in the basin with capacities in excess of 500 acre-feet, and a
<br />collective storage volume of 2,2 million acre-feel The major instream reservoirs on the main stem are
<br />Antero, Spinney, Eleven Mile, CheesDlllll, and Chatfield, The major storage facilities that exist on ofIstream
<br />sites or on tributaries are Cheny Creek Reservoir, Barr Lake, Carter Lake, Horsetooth Reservoir, Riverside
<br />Reservoir, Empire Reservoir, Prewitt Reservoir, North Sterling Reservoir, and Julesburg Reservoir,
<br />The South Platte River is a headwaters system, therefore there are no significant surface water inflows
<br />from upstream river systems, with the exception of interbasin transfers from west of the Continental Divide,
<br />Native water basin yields are estimated 10 be 1.44 million acre-feet annually, with average annual water
<br />imports of 400,000 acre-feet. Average annual surface water flows leaving the state at Julesburg are 393,000
<br />acre-feet, with annual ground water outflow from the alluvial aquifer averaging 15,000 acre-feet.
<br />In addition 10 surface water, ground water is used extensively throughout the basin for irrigation,
<br />municipal, domestic, and industrial water supplies, and livestock. It is available from alluvial aquifers in
<br />stream valleys, consolidated aquifer systems underlying the plains, and fractured systems of the metamorphic
<br />and granite rocks of the front range, Wells completed in the alluvial aquifer system
<br />provide high yields, whereas wells completed in fractured rock in the mountains produce low yields, The two
<br />primaty aquifer systems in the basin are the South Platte alluvial aquifer, and the Denver Basin aquifer. The
<br />Denver Basin aquifer is composed of four major bedrock aquifers.
<br />The alluvial aquifer system is recharged by infiltration of seepage from streams, reservoirs, and ditches,
<br />and by deep percolation of precipitation aruhppliffi irrigation water, The direction of ground water flow is
<br />normally toward the river from recharge sites, Inigation return flows in the form of both surface and ground
<br />water contribute to streamflow, Ground water levels within the alluvial system can decline during the year
<br />because of pumping for irrigation; however, these declines are not a significant problem within the South
<br />Platte alluvial system. Approximately 680,000 acre-feet of ground water was withdrawn from the alluvial
<br />aquifer for irrigation purposes in 1993,
<br />Ground water discharge from the alluvial aquifer to the river in the South Platte system is variable from
<br />one location to another and is related to saturated thickness and ground water level of the alluvial aquifer.
<br />Comparisons of estimated basin inflows and water diversions indicate that water diversions and withdrawals
<br />greatly exceed the total amount of water available. Thus, a significant portion of the irrigation water demand
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