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• Piezometric surfaces in deeper formations such as the lower Dakota, Burro Canyon, Morrison and <br />Entrada Formations whose ground water is under artesian pressure closely conforms to structural <br />influence (Lohman, 1965). In these formations, recharge occurs along structural highs, i.e., an <br />outcrop which corresponds to the limb of a syncline or the fractured crest of an anticline. Movement <br />of water within these formations is down dip with faults acting as boundary conditions or conduits <br />for flow. These artesian waters are the principal suppliers of water to areas near Grand Junction <br />which is northwest of WFC's New Horizon mining operation. <br />Regional Ground Water Recharge. Movement and Discharge. The principal areas of ground <br />water recharge are in the plateaus and mountains, which receive the greater amounts of annual <br />precipitation. Ground water movement is from areas of recharge to areas of natural discharge, <br />which include springs, gaining reaches of springs and areas of phreatophyte growth. Ground water <br />consumption by phreatophytes and hydrophytes in the Colorado and Utah parts of the upper <br />Colorado Region has been estimated by Robinson (1958) to be more than 2 million acre-feet per <br />year. Ground water occurs under both water table and artesian conditions. Water table conditions <br />commonly exist in shallow alluvial aquifers along the largerstreams, in principal recharge areas, and <br />in the relatively flat-lying rocks that predominate certain sections of the region. Artesian conditions <br />occur locally throughout the region but are prevalent in the bedrock aquifers of the major structural <br />basin. <br />• Regional Ground Water Quality. In the upper Colorado Region, fresh water is generally available <br />from shallow aquifers in most consolidated units in areas above 7,000 feet in elevation. At lower <br />elevations, fresh water most commonly occurs in the relatively permeable sandstones and <br />carbonate rocks, which have good hydraulic connection with the principal recharge areas in the <br />mountains. Saline water commonly occurs in shale and siltstone strata that underlie large areas of <br />the region. <br />The relatively large, discharge-weighted-average concentration of dissolved solids in the streamflow <br />in various parts of the region results partly from inflow of saline ground water from formations like <br />the Mancos shale and the Paradox Formation. Ground water in the alluvium generally contains <br />more dissolved solids than streams. The principal reasons for this are the concentrating effects of <br />evapotranspiration and the solution of minerals in the alluvium. <br />The quality of ground water in many parts of the region is altered by man's activities. The seepage <br />of highly mineralized irrigation return flow from surface sources into aquifers can deteriorate the <br />quality of water in those aquifers. The change in San Miguel water quality at Uravan is a reflection <br />of this. Deteriorization of ground water also results from pumpage stresses. Poorer quality saline <br />• water can be induced from adjacent aquifers. Some fresh water aquifers in the region are either <br />(REVISED JULY 2006) 2.04.5-8 <br />