FLOOD08209 - Laserfiche WebLink

Home Browse Search

, SECT ION I X GROUNDWATER RESOURCES IX-l The transient groundwater storage in the alluvial aquifer of the South Platte River between Chatfield Reservoir and Brighton total approximately 330,000 acre-feet. Of this total, approximately 30,000 acre-feet are in transient storage between Chatfield Reservoir and the 19th Street gaging station in Denver (Wright, 1968). From 19th Street to Brighton, the ground- water within the alluvial aquifer of the South Platte River is approximately 300,000 acre-feet (Bittinger, 1968). The 19th Street gaging station is the boundary between Water District Nos. 8 and 2 of Irrigation Division No.1 as administered by the State Engineer of Colorado. same aquifer is the water supply for the City of Brighton. South Platte alluvial wells in the vicinity of the Fulton Ditch headgate have been pro- posed for use by the City of Northglenn. Wells are depended upon by the agricultural industry in the South Platte River valley. It is necessary that the Master Planning of the South Platte River consider the groundwater resource along the South Platte River, and that proposed improvements are compatible with the long-term utilization of this important resource for municipal, agricultural, industrial, and domestic use. Development of the South Platte alluvial groundwater resources in Water Dis- trict No.8 (Chatfield to 19th Street) is accomplished via wells constructed for municipal, irrigation and other purposes. There are nearly 100 alluvial wells in this reach (Hillier, 1983) which have been used for water table measurements between 1954 and 1976. Depth to Water Table The depth to the water table along the South Platte River is a factor in planning. For instance, depth to water table effects road and highway stability, soil salinity problems, the type of vegetation that can be grown, building foundations, feasibility of basements, and gravel mining. Primar- ily, however, depth to water table relates to the ability to construct and develop good yielding wells for water supply purposes. Downstream of 19th Street to Baseline Road, alluvial groundwater development along the South Platte River has been extensive. A survey of all alluvial wells in all of Water District No.2 performed in 1968 listed 1,552 irriga- tion well registrations having an average yield of 1.8 cfs each (Bittinger, 1968). In addition, Bittinger estimated that there were an additional 260 commercial, industrial and municipal wells havin9 an average yield of approximately 0.5 cfs each. Approximately 30 percent of the mainstem of the South Platte River in District No.2 lies within the reach from 19th Street to Baseline Road (City of Brighton). Between 19th Street and Baseline Road Bittinger estimated that the average pumping withdrawals from this portion of the river alluvium amounted to of 40,000 acre-feet per year, Adjacent to the South Platte River, from Sand Creek to Brighton, the water table adjacent to the mainstem of the river is designated by the U.S. Geo- logical Survey as being less than 5 feet deep. Surrounding, and adjacent to this zone of shallow water, and along the full reach of the river in the floodplain, the water table is designated as being from 5 to 10 feet deep, Along the right bank for the full river length from Sand Creek to Brighton, the alluvial groundwater extends eastward for, in some places, as much as 7 mi 1 es, Through the City of Denver from Sand Creek to Big Dry Creek in ,. Englewood, the depth to water table adjacent to the~.r-,Wer is from 10 to 20 feet. From Big Dry Creek to Chatfield Reservoir the water table is again shallow, rangin9 from 10 feet to less than 5 feet. ~ The alluvial groundwater resource is an important economic component of the South Platte River floodplain. Groundwater has value to the Denver Metro region. Groundwater from the South Platte River alluvium provides a major source of water for the City of Thornton during the summer months. This Evaluation of depth to water table indicates that river channelization, and confining of the river within narrow fixed banks, results in lower water tables due to the fact that the deep channel serves as a deeper groundwater drain. Therefore, when deepening a river channel for additional flood carrying capacity, the effect on adjacent groundwater tables must be con- sidered. A deeper river channel means lowered water tables.