Laserfiche WebLink
2.04.7 Hydrology Description <br />• gulches, "QS{~z" in Stephen's Draw, and "Q1s2' in C-Gulch. The most significant of <br />these deposits are the "Qas"deposits at the head of Freeman and Dove gulches. <br />These unconsolidated quaternary deposits are the primary sources of springs <br />and seeps within the Permit Area. Typically, discharge is small (less than 5 gpm) <br />and conductivity low to moderate (100-500 umhos/cm -refer to groundwater <br />monitoring results). The recharge -discharge relationship are functions of <br />geomorphology and seasonal variations in precipitation. Recharge occurs <br />because of percolation and infiltration in the topographically lower stream <br />drainages. Many of the discharges are also associated with small scale mass <br />wasting features, where presumably near surface groundwater flow saturates the <br />regolith, resulting in slump structures with attendant springs and seeps and <br />infiltrates back into the colluvium. Cumulative discharge represents no total run- <br />off, and most of the available near surface groundwater is believed to be <br />transpired by native vegetation. Wymore (1974) states, "that natural plant <br />associations have normal evapotranspiration rates that far exceed normal <br />precipitation during the growing season, which effectively prevents deep <br />percolation losses during most of the year" for the Piceance and Yellow Creek <br />watersheds of West-Central Colorado. <br />The significance of spring discharges to maintaining streamflow is nonexistent. <br />The evapotranspiration demands of vegetation, small cumulative discharge, and <br />gain-loss data presented by Brooks (1982) suggests that streams traversing the <br />permit area are losing flow, and spring discharge does not enhance the <br />ephemeral nature of streamflow. The significance of springs to maintaining the <br />land use patterns of the area is described in section 2.05.6(6), subsidence. <br />Generally, colluvial springs are marginally suitable and small discharges preclude <br />any agricultural or aquatic use. <br />colluvial springs are typically characterized by total dissolved solids values less <br />than 1,000 mg/I and are differentiated from the bedrock water by lower <br />conductivity and TDS. The lower values suggest shorter residence time in the <br />regolith (refer to groundwater monitoring results). <br />The area of colluvial sediments are very limited in extent. None of the areas can <br />be classified as an alluvial valley floor as it does not meet the requirements of <br />irrigation, topographic, or geographic conditions. Except for livestock and wildlife <br />use of springs and ponds, there are no known uses of groundwater in the permit <br />and adjacent area. <br />Riparian vegetation occurs near the seeps in the colluvial material. A few <br />willows, sedges, grasses and other riparian vegetation extend from the seeps to <br />the colluvial deposits. They are not extensive. <br />Groundwater occurrences within the Mesaverde formation have been analyzed <br />using the piezometer data gathered for the mine site area. That data shows that <br />• there is groundwater in the coal seam but, as described earlier in this report, <br />should not be of any significant influence to the hydrologic regime. <br />PR-10 2.04 - 30 - 10/08 <br />/~PPRavco <br />