Laserfiche WebLink
<br />Section 3 <br />Physical Environment of the South Platte Basin and Denver/South Metro Counties <br /> <br />The alluvial aquifer is estimated to contain as much as <br />8.3 million AF in storage and is hydraulically connected <br />to the river (CGS 2003). Therefore, groundwater <br />withdrawals, of which the majority are junior in priority to <br />most surface water rights, can greatly affect the flow of <br />the lower South Platte River. This segment, which is <br />downstream of metro Denver, gives rise to the need for <br />well augmentation plans to protect senior water rights. <br /> <br />In the lower South Platte River alluvium, there are <br />approximately 10,880 permitted wells with yields ranging <br />in capacity from 1 to 3,000 gpm. The average yield is <br />430 gpm; however, 50 percent of the wells have a yield <br />of 30 gpm or less, which is biased by domestic wells <br />(CGS 2003). <br /> <br />The Denver Basin aquifers, which cover approximately <br />6,800 square miles, are comprised of the Dawson, <br />Denver, Arapahoe, and Laramie-Fox Hills aquifers, are <br />another important water resource for the South Platte <br />Basin. The Denver Basin consists of Tertiary and <br />Cretaceous age sedimentary rocks that supply <br />groundwater for domestic, commercial, municipal, <br />agricultural, and other users (CGS 2003). <br /> <br />There are also five Designated Groundwater Basins in <br />the South Platte Basin, which include the Upper Crow <br />Creek, Camp Creek, Northern High Plains, Lost Creek, <br />and Kiowa-Bijou. Designated groundwater is water that <br />under natural conditions would not be used to recharge <br />or supplement continuously flowing surface streams <br />(Hobbs 2003). <br /> <br />The Northern High Plains aquifer, which includes the <br />Ogallala aquifer located in the Republican River Basin, is <br />found in the eastern edge of Colorado in the High Plains <br />region and is a major source of water for this agricultural <br />region (CDPHE 2002). Groundwater withdrawals have <br />exceeded recharge since the early 1960s. The mean well <br />yield from this aquifer is 373 gpm and the median is <br />20 gpm (CGS 2003). <br /> <br />3.2.8 Water Quality <br /> <br />There is a broad range of water quality in the South <br />Platte Basin and Denver/South Metro Counties, ranging <br />from high-quality mountain streams to those impacted <br />due to urbanization and agricultural activities. <br /> <br />The upper South Platte River watershed is an area that <br />has been affected by historic mining districts (i.e., <br /> <br />S:\1177\Basin Reports\South Platte\S3_South Platte.doc <br /> <br />Mosquito Creek), water resource development (i.e., <br />South Park Dams and water diversions), and severe <br />sediment deposition from forest fires such as the recent <br />Hayman, Buffalo Creek and Hi Meadows fires <br />(CDPHE 2002). <br /> <br />The middle reach of the watershed, from below Chatfield <br />Reservoir to the confluence with the Cache la Poudre <br />River, has experienced some of the most intense use <br />and resultant impacts of any river in Colorado. This <br />segment of the river has seen historic mining districts, <br />explosive urban development, stormwater runoff, <br />extensive hydrologic modification, urban and agricultural <br />nutrient loading, and effects of Superfund sites. <br />Pollutants that have impaired the waters of the South <br />Platte Basin include nitrate, ammonia, and copper <br />(CDPHE 2000). Furthermore, the South Platte River <br />through and downstream of the Denver urban area <br />exceeds E. coli standards (CDPHE 2002). <br /> <br />The lower reach of the South Platte River, from the <br />Cache la Poudre River to Julesburg, has been affected <br />by upstream urbanization, historic agricultural land use, <br />and waste disposal due to animal feeding operations. <br />Non-point source pollution from pesticide and fertilizer <br />runoff is the primary concern in this segment of the lower <br />South Platte River (CDPHE 2002). <br /> <br />Downstream of the Denver area, groundwater in the <br />alluvial aquifer exceeds the nitrate limit for drinking water <br />standards in some areas. The nitrate contamination not <br />only affects the drinking water supply of several eastern <br />plains cities, but can also be detrimental to certain crops <br />when used for irrigation (CDPHE 2002). <br /> <br />Groundwater in the alluvial aquifer near Denver contains <br />approximately 1,000 parts per million (ppm) total <br />dissolved solids (TDS). This concentration increases to <br />about 4,000 ppm near Sterling. Surface water at the <br />state line with Nebraska has an average TDS <br />concentration of 1,300 ppm (CGS 2003). These <br />concentrations are of concern because water containing <br />greater than 2,000 ppm TDS is generally considered to <br />be unsuitable for irrigation (CDPHE 2002). <br /> <br />CONI <br /> <br />3-9 <br />