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-Colorado Geological Survey
<br />0 100 Miles
<br />DRAFT
<br />EXPLANATION
<br />Outcrop of Dakota
<br />Sandstone
<br />Outcrop of
<br />a
<br />pre- Cretaceous rocks
<br />Total Dissolved Solids
<br />Concentrations (mg /L)
<br />y =, -
<br />>2,000
<br />1,000 -2,000
<br />500 -1,000
<br /><500
<br />Limit of the Dakota -
<br />Cheyenne aquifer in
<br />subsurface
<br />Fault
<br />=igure 6.8 -5. Total dissolved
<br />olids concentrations in the
<br />)akota- Cheyenne aquifer in
<br />:astern Colorado.
<br />4 it � 141'44,1 14, 411 O'sI',''It & *a& &0,* V S_V & & &tom &0.SA'a S-
<br />GROUND -WATER ATLAS OF COLORADO
<br />WATER QUAL /TY
<br />Water quality within the Dakota - Cheyenne aquifer is generally good, but is dependent
<br />upon the geologic composition of the unit. The total dissolved solids (TDS) concentra-
<br />tions of the ground water in this aquifer typically range from 200 to 25,000 milligrams
<br />per liter (mg /L) and correlate nicely with specific conductance. Figure 6.8 -5 presents
<br />the general distribution of dissolved solids concentrations from the Dakota - Cheyenne
<br />aquifer in eastern Colorado. The complex stratigraphy in the northern portion of the
<br />aquifer produces highly variable, non - uniform water chemistry (Robson and Banta,
<br />1987). Large TDS concentrations are prevalent in the oil and gas fields and are most
<br />likely related to the depositional environment associated with these deposits. In areas
<br />of southern Colorado, TDS concentrations decrease as the water moves eastward due
<br />to recharge mixing, ranging from 250 to 500 mg /L in much of Baca and southeastern
<br />Prowers counties (Robson and Banta, 1987). In general, ground water along the basin
<br />recharge areas is of a calcium bicarbonate type, becoming a sodium bicarbonate type
<br />as it moves eastward in northern Colorado.
<br />SELECTED REFERENCES
<br />Boettcher, A.J., and Horr, A.C., 1964, Geology and ground -water resources in eastern Cheyenne
<br />and Kiowa counties, Colorado: U.S. Geological Survey Water Supply Paper 1779 -N,
<br />p. N1 -N16, N30 -N32.
<br />Craigg, S.D., Dam, W.L., Kernodle, J.M., and Levings, G.W., 1989, Hydrogeology of the Dakota
<br />Sandstone in the San Juan structural basin, New Mexico, Colorado, Arizona, and Utah:
<br />U.S. Geological Survey Hydrologic Investigation Atlas HA- 720 -I, 2 sheets, scale
<br />1:1,000,000.
<br />Freethey, G.W., Kimball, B.A., Wilberg, D.E., and Hood, J.W., 1988, General hydrogeology of
<br />aquifers of Mesozoic age, upper Colorado River basin: U.S. Geological Survey Hydro-
<br />logic Investigation Atlas HA -698, 2 sheets, scale 1:2,500,000.
<br />McLaughlin, T.G., 1954, Geology and ground water resources of Baca County, Colorado: U.S.
<br />Geological Survey Water Supply Paper 1256, 232 p.
<br />Pearl, R.H., 1982, Dakota aquifer system in the state of Colorado, in Geohydrology Dakota
<br />Aquifer Symposium: Lincoln, Nebraska, National Water Well Association, p. 156 -162.
<br />Robson, S.G., and Banta, E.R., 1987, Geology and hydrology of the deep bedrock aquifers in
<br />eastern Colorado: U.S. Geological Survey Water Resources Investigation WRI 85 -4240,
<br />6 sheets.
<br />Romero, J.C., 1994, The Dakota and Cheyenne aquifers in the Cheyenne- WellsLas Animas
<br />region, Colorado: Colorado Division of Water Resources Investigation 94 -1, 22 p.
<br />Vinckier, T.A., 1982, Hydrogeology of the Dakota Group aquifer with emphasis on the radium -
<br />226 content of its contained ground water, Canon City embayment, Fremont and Pueblo
<br />counties, Colorado: Colorado Geological Survey, Open -File Report 01782 -03, 80 p., 8 pls.
<br />Voegeli, P.T., and Hershey, L.A., 1965, Geology and ground water resources of Prowers County,
<br />Colorado: U.S. Geological Survey Water Supply Paper 1772, 101 p.
<br />Weist, W.G., Jr., 1963, Water in the Dakota and Purgatoire Formations in Otero County and the
<br />southern part of Crowley County, Colorado: U.S. Geological Survey Water Supply Paper
<br />1669 -P, p. P1 -P17.
<br />Weist, W.G., and others, 1965, Geology and occurrence of ground water in Otero County and
<br />the southern part of Crowley County, Colorado: U.S. Geological Survey Water Supply
<br />Paper 1799, 90 p.
<br />Young, R.G., 1970, Lower Cretaceous of Wyoming and southern Rockies: Mountain Geologist,
<br />v. 7, no. 3, p. 105 -121.
<br />SP 53
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