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• Respond to the recommendations detailed in the April 1998 Senate Bill 96-74 study, <br />Denver Basin and South Platte River Basin Technical Study (Colorado Water <br />Conservation Board and State Engineers Office 1998). <br />• Have the capacity to be an extension of, and compatible with, the existing CRDSS, and <br />the nearly complete RGDSS <br />• Respond to those situations and concerns in the study area which differ in some respects <br />from the Rio Grande and Colorado River basins; e.g., multiple groundwater systems, <br />increased urbanization of agricultural lands and the consequent transfer of irrigation water <br />rights to municipalities, increased runoff from impervious areas in rapidly urbanizing <br />portions and lawn irrigation return flows <br />1.2 BASIN CONDITIONS <br />1.2.1 South Platte River Basin <br />The South Platte River basin begins in the South Park area of the Rocky Mountains in central <br />Colorado and flows southeast to near Divide, Colorado (see Figure 1-1). Here the river turns <br />sharply northeast and flows through the Front Range via Waterton Canyon, where it emerges on <br />the plains of the Colorado Piedmont southwest of Denver. Continuing its northeastern course, <br />the South Platte River flows through Denver to near Greeley, Colorado, where it bends eastward <br />to Sterling, Colorado and North Platte, Nebraska. There it j oins the North Platte River to form <br />the Platte River after flowing a distance of 442 miles from its source (U. S. Geological <br />Survey 2000). Major tributaries of the South Platte include Tarryall Creek, the North, Middle <br />and South Fork of the South Platte, Plum Creek, Bear Creek, Cherry Creek, Clear Creek, St. <br />Vrain Creek, the Big Thompson and Cache La Poudre Rivers. Major reservoirs on the mainstem <br />of the South Platte River include Antero, Spinney Mountain, Eleven Mile Canyon, Cheeseman <br />and Chatfield. There are no on-channel reservoirs below Chatfield Reservoir, but there are a <br />number of off-channel reservoirs that fill from the South Platte River. <br />The South Platte River basin has a continental type climate modified by topography in which <br />there are large temperature ranges and irregular seasonal and annual precipitation (U.S. <br />Geological Survey 2000). Mean temperatures increase from west to east and on the plains from <br />north to south. Areas along the Continental Divide average 30 inches or more of precipitation <br />annually which includes snowfall in excess of 300 inches. In contrast, the annual precipitation <br />on the plains east of Denver and in the South Park area in the southwest part of the basin ranges <br />from 7 to 15 inches (U.S. Geological Survey 2000). In general, most of the precipitation falls as <br />rain in the late spring and as snow during late winter, with very dry conditions in between. <br />The South Platte River basin (see Figure 1-1) within Colorado is located in the northeast section <br />of the State of Colorado and is comprised of 18 counties with a 1999 population of 2,855,181 <br />(Colorado Department of Local Affairs 2001). Of that total, 2,318,178 live in the six-county <br />(Adams, Arapahoe, Boulder, Denver, Douglas and Jefferson) metropolitan area, as compared to <br />1,854,304 in the six-county area in 1990 (Colorado Department of Local Affairs 2001). This <br />p:data\gen\spdss\final report\chapter l.doc 1-3 <br />October 31, 2001 <br />