| Popis: |
Stratigraphic, hydraulic, and water-level data obtained from water-well and petroleum test-hole records indicate that the Mesozoic rocks in the Upper Colorado River Basin include many potential aquifers. Structural deformation during late Mesozoic and early Cenozoic time caused large parts of the most productive aquifers to be removed by erosion; other parts are deeply buried by younger deposits. Three hydrogeologic units include aquifers. The lower unit consists of the Moenkopi and Chinle Formations. The middle unit consists of the Glen Canyon Group, the San Rafael Group, and the Morrison Formation; all containing sandstone aquifers. The Glen Canyon Group is only partly saturated where it crops out. It may contain from 600 to 1200 million acre-feet of drainable water in storage, but only a fraction is feasibly recoverable. The upper unit consists of two aquifer systems, the Mesaverde and Dakota systems, separated by a confining system, the Mancos Shale. Primary hydraulic-conductivity values are characteristically less than 10 feet per day. Fracturing increases hydraulic conductivity values near land surface; however, the thicker the overburden, the less likely the effect of this secondary permeability factor. The large volume rather than permeability of saturated rock accounts for the favorable water-supply potential of the Mesozoic agemore » formations. . Where the middle hydrogeologic unit occurs near the surface or only at shallow depths it contains fresh to slightly saline water. Where deeply buried it contains water with concentrations of dissolved solids greater than 35,000 milligrams per liter (brine). The Mesaverde Group also contains water of varying quality; however, the sandstone lenses that contain usable water supplies are only locally continuous. Where the formation is deeply buried, it contains brine. 16 refs., 20 figs., 2 tabs.« less |
