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<br />. <br /> <br />..r"'''. ") <br />liIJ ;),. <br /> <br />table contours (Hurr, et al.,' 1975) indicates that the South Platte River <br /> <br /> <br />may be considered as a gaining stream throughout the study area. Since <br /> <br /> <br />the a~uifer is hydraulically connected to the river, any changes in pumpage <br /> <br /> <br />from or recharge to the aquifer will have an effect on the flow in the <br /> <br /> <br />river. The magnitude and timing of these effects depend, to a large degree, <br /> <br /> <br />on the distance from the river at which the changes in pumpage or recharge <br /> <br /> <br />occur. These effects will be discussed later. <br /> <br /> <br />Depths to water range from less than 10 feet to about 100 feet and <br /> <br /> <br />saturated thickness ranges from zero to over 240 feet. In general, depths <br /> <br /> <br />to water are shallowest and saturated thickness is greatest nearest the <br /> <br /> <br />river. Depths to water are greatest and saturated thickness is least at <br /> <br /> <br />the outer extremities of the alluvial deposits. <br /> <br />. <br /> <br />Aquifer Characteristics <br /> <br />, <br />The a~uifer characteristics of interest are transmissivity, permeability, <br /> <br /> <br />and specific yield, Information regarding these parameters may be found <br /> <br /> <br />in USGS Water Supply Paper No. 1378 (1957) and in a series published by the <br /> <br /> <br />Water Resources Division of the USGS dealing with the hydrogeologic charac- <br /> <br /> <br />teristics of the valley-fill aquifer of the South Platte River Valley (Hurr <br /> <br /> <br />and Schneider, 1972). <br /> <br />-I: <br />..... <br /> <br />Transmissivities determined by pumping tests at six sites in the <br /> <br /> <br />alluvium ranged from 44,000 gallons per day per foot (gpd/ft) to 290,000 <br /> <br /> <br />gpd/ft. Corresponding permeabilities varied from 490 gpd/ft2 to 3160 gpd/ft2 <br /> <br /> <br />(65 ft/day to 421 ft/day). Transmissivities in the study area, however, <br /> <br /> <br />range from zero in some areas nearest the a~uifer boundaries to over <br /> <br /> <br />800,000 gpd/ft in some areas near the river. In general, the aquifer trans- <br /> <br /> <br />missivity averages about 50,000 gpd/ft in areas where recharge would be <br /> <br /> <br />implemented. Saturated thickness in these areas is about 50 ft indicating <br /> <br /> <br />an average permeability of about 1000 gpd/ft2 (134 ft/day). This appears to <br /> <br /> <br />be a typical value for sand and gravel deposits and was used for all <br /> <br /> <br />computations in this study. <br /> <br />. <br />