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<br />Section 3
<br />Physical Environment of the South Platte Basin and Denver/South Metro Counties
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<br />I l!l~!
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<br />3.2.6 Surface Water
<br />
<br />The South Platte River emerges out of the mountains
<br />southwest of the Denver metro region, flows through the
<br />Denver metropolitan urban area, and then enters the
<br />High Plains Region (Woodward-Clyde Consultants
<br />1982).
<br />
<br />Major mountain tributaries to the South Platte River from
<br />upstream to downstream include the North, Middle, and
<br />South Forks of the South Platte River (upstream of
<br />Chatfield Reservoir), Bear Creek, Clear Creek, St. Vrain
<br />Creek, the Big Thompson River, and the Cache la
<br />Poudre River, as shown in Figure 3-2. Tributaries from
<br />the Plains region include Plum, Cherry, Sand Creek, Box
<br />Elder, Kiowa, Bijou, Badger, Beaver, and Wildcat
<br />Creeks. The tributaries as well as the South Platte River
<br />have highly variable streamflows, with snowmelt runoff
<br />and summer thunderstorms dictating the flow in the
<br />spring and summer.
<br />
<br />The USGS monitors these streamflows with various
<br />gages located throughout the basin. Figure 3-5 shows
<br />the location of four selected streamflow gages in the
<br />South Platte Basin as well as major diversions in the
<br />basin and segments with decreed instream flow rights.
<br />Table 3-2 summarizes the mean annual streamflow,
<br />length of record and drainage area for each selected
<br />gage location.
<br />
<br />3.2.7 Groundwater
<br />
<br />Groundwater is a substantial resource in the South Platte
<br />Basin. Approximately 880,000 acre-feet per year (AFY)
<br />of groundwater in the South Platte Basin is used for
<br />irrigation, and 100,000 AFY is used to meet municipal,
<br />domestic, livestock, industrial, and commercial purposes.
<br />These values do not include groundwater pumped from
<br />the Ogallala Aquifer. Residents in Phillips, Yuma,
<br />Washington, Kit Carson, Cheyenne, Lincoln, and Elbert
<br />counties rely almost entirely on groundwater. Those
<br />living in the counties of Sedgwick, Morgan, Weld,
<br />
<br />Adams, and Douglas also use groundwater to meet a
<br />large portion of their water demand (CGS 2003).
<br />
<br />Figure 3-6 shows the location of the significant aquifers
<br />throughout the South Platte Basin and wells with
<br />permitted or decreed capacities greater than or equal to
<br />500 gallons per minute (gpm). These aquifers are as
<br />follows:
<br />
<br />. Alluvial Aquifer
<br />. Dawson
<br />. Denver
<br />. Arapahoe
<br />. Laramie-Fox Hills
<br />. Upper Cow Creek
<br />. Camp Creek
<br />. Northern High Plains
<br />. Lost Creek
<br />. Kiowa-Bijou
<br />
<br />As shown in Figure 3-6, the bedrock aquifer is comprised
<br />of the Dawson, Denver, Arapahoe, and Laramie-Fox
<br />Hills. The designated groundwater basins include the
<br />Upper Crow Creek, Camp Creek, Northern High Plains,
<br />Lost Creek, and Kiowa-Bijou aquifers.
<br />
<br />The reach of the South Platte River that begins
<br />southwest of the Denver Metro area and continues
<br />downstream to the state line is underlain by valley fill
<br />sediment forming the alluvial aquifer. This alluvial aquifer
<br />is composed primarily of poorly sorted gravel, sand, and
<br />clay. The saturated alluvium increases from 20 feet near
<br />Denver to over 200 feet at Julesburg with the thickest
<br />section running along the center of the historic river
<br />channel (CGS 2003).
<br />
<br />Table 3-2 Summary of Selected USGS Stream Gages for the South Platte River Basin and Denver/South Metro Counties
<br />
<br /> Mean Annual Mean Annual
<br /> USGS Site Streamflow Streamflow Period of Drainage
<br />Site Name Number (AFY) (cfs) Record (Years) (sq. miles)
<br />Poudre 06752000 T 270,981 T 374 T 1881-2002 T 1,056
<br />South Platte at South Platte 06707500 289,740 400 1896-2002 2,579
<br />South Platte at Kersey I 06754000 I 651,466 I 900 I 1901-2002 I 9,598
<br />South Platte at South Julesburg 06764000 395,314 546 1902-2002 23,193
<br />Source: USGS NWISweb/HydroBase database
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<br />CONI
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