Hydrologic properties and ground-water flow systems of the Paleozoic rocks in the upper Colorado River basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

Abstract

The Regional Aquifer-System Analysis (RASA) program was started in 1978 after a congressional mandate to develop quantitative appraisals of the major groundwater systems of the United States. The RASA program represents a systematic effort to study a number of the Nation's most important aquifer systems which, in aggregate, underlie much of the country and which represent important components of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and accordingly transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies, both to develop an understanding of the natural, undisturbed hydrologic system, and of any changes brought about by human activities, as well as to provide a means of predicting the regional effects of future pumping or other stresses. The final interpretive results of the RASA program are presented in a series of U.S. Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of each regional aquifer system. Each study within the RASA program is assigned a single Professional Paper number, and where the volume of interpretive material warrants, separate topical chapters that consider the principal elements of the investigation may be published. The series of RASA interpretive reports begins with Professional Paper 1400, and thereafter will continue in numerical sequence as the interpretive products of subsequent studies become available.

Groundwater and surface-water resources in the Bureau of Land Management Moab Master Leasing Plan area and adjacent areas, Grand and San Juan Counties, Utah, and Mesa and Montrose Counties, Colorado

“…During Cambrian through Early Mississippian time, the entire Colorado Plateau received only thin marine sediments as a result of occasional advancements of the Cordilleran seas to the west (Hanshaw and Hill, 1969) including the Leadville Limestone and equivalents, the Ouray Limestone, the Elbert Formation Limestones, and the Lynch Dolomite (Geldon, 2003). These sedimentary rocks consisting of limestone, fine-grained clastics, and interbedded evaporites have been observed (Jobin, 1962), although minimal exposures have been discussed in previous studies.…”

“…The geologic setting and history of the study area is preserved in rocks and geologic structures that span more than 1 billion years (Geldon, 2003). Rocks and sediments exposed in the study area are Paleozoic to Quaternary in age; Mesozoicage sedimentary rocks, however, dominate the study area.…”

“…Although the thickness of Mesozoic rocks in the southern region of the UCRB (less than 5,000 ft) is less than thicknesses in the northern region of the UCRB (greater than 5,000 ft), 50-75 percent of this Mesozoic rock thickness in the southern UCRB is aquifer material, indicating that only 25-50 percent of less than 5,000 ft needs to be penetrated to tap the aquifers, decreasing groundwater-withdrawal costs (Freethey and Cordy, 1991). Geldon (2003) later described the hydrologic properties and groundwater-flow systems of the deeper Paleozoic aquifers in the UCRB.…”

“…Rocks and sediments exposed in the study area are Paleozoic to Quaternary in age; Mesozoicage sedimentary rocks, however, dominate the study area. Archean-and Proterozoic-age granitic and metamorphic rocks underlie the study area (Geldon, 2003).…”

“…Based on studies by Rush and others (1982), Weir and others (1983), Freethey and Cordy (1991), Geldon (2003), and Lowe and others (2007), eight principal aquifers and six confining units were identified in the study area (table 1). Generally, the aquifers can be split into four types: (1) limestone aquifers of marine origin, (2) sandstone aquifers of eolian and marine origin, (3) sandstone and conglomerate aquifers of fluvial origin, and (4) valley-fill aquifers in unconsolidated deposits.…”