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<br />1 <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />HYDROLOGY <br /> <br />II-3 <br /> <br />FLOOD CONTROL STORAGE <br />The South Platte River flood potential is mitigated by Chatfield, Cherry <br />Creek and Bear Creek flood control reservoirs. The study area is directly <br />affected only by Chatfield Reservoir. The location of these reservoirs is <br />shown on Figure II-I. Tributaries enter the mainstem of the South Platte <br />River downstream of these reservoirs which increases the flood potential <br />below the reservoirs. Flood control storage available in these reservoirs <br />is shown in Table II-2. The river discharge regime as a result of the <br />proposed Two Forks Reservoir and increased municipal use have been <br />evaluated. Results are presented later :in this chapter. <br /> <br /> TABLE B-2 <br /> FLOOD CONTROL RESERVOIRS <br /> Storage (Acre-feet) <br /> Permanent* Clos u re <br />Reservoir Total Pool Flood Control Surcharge Date <br />Chatfield 235,000 26,661 208,370 119,900 08/1973 <br />Cherry Creek 93,920 13,960 79,960 134,470 10/1948 <br />Bear Creek 30,810 1,990 26,570 46,410 07/1977 <br /> <br />* Permanent pool storage includes recreational/multipurpose pools and <br />sediment control volumes. <br /> <br />PEAK FLOWS <br />A majority of the precipitation which falls over the South Platte River <br />basin consists of snowfall in the mountainous region and thunderstorm <br />activity in the high plains and foothills portions of the basin. Snowfall <br />in the mountains and higher foothills results in runoff peaks in the late <br />spring; however, these peaks are reduced by Chatfield Dam. Snowmelt:in the <br />lower foothills and high plains is not normally associated with sharp or <br />