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- I <br />• 7 . 2 DEPTH TO GF FUND WATER , f. _ ~ -j ~ -j <br />~. \' ,~ V '~ 1~ <br />Ground water is less than 400 feet deep. <br />Topography and geology control ground-water depths. <br />The depth to ground water depends mostly upon the topographic <br />position of the well. In stream valleys, ground water is less than <br />100 feet deep because the valleys intercept ground water flowing <br />through the bedrock.and force the water to the surface (fig. 7.2-1); <br />some of this water discharges as springs or flows into stream alluvium. <br />The alluvium also stores and transmits water infiltrating from <br />precipitation and storm and snowmelt runoff. In the Raton Basin, <br />• the alluvium is saturated as much as 20 feet above. the bedrock <br />near the streams and much less on the edges of valleys. Springs <br />discharge from the alluvium where the underlying bedrock is near <br />the surface or where dikes and sills cross the channels. On stream <br />divides, permeable formations are drained by seeps and springs <br />discharging into the valleys, and wells may have to be drilled <br />as much as 400 feet deep to obtain water. In figure 7.2-2, which <br />shows the depth to ground water in a part of the basin for which data <br />are available., areas of shallow ground water generally coincide with <br />valleys, and areas of deep ground water generally coincide with <br />stream divides. <br />The depth to ground water is also affected by the geology. An <br />extensive area of shallow ground water north of the Apishapa River <br />(fig. 7.2-2) coincides with outcrop areas of the. highly permeable <br />Poison Canyon-Cuchara aquifer (fig. 7.2-3). Clusters of springs <br />55 <br />