Figure 1.1 Generalized geologic map of Colorado.
Table 1.1 Geologic events and deposits in Colorado through time.
Figure 1.2 Principal aquifers and structural basins of Colorado.
Figure 1.3 Average annual water balance in Colorado.
Figure 1.4 Distribution of ground- versus surface-water withdrawals by county in 1995.
Figure 1.5 Distribution of ground-water withdrawals during 1995.
Figure 2.1 Porosity and permeability of common geologic units that form aquifers.
Figure 2.2 The hydrologic cycle describes the circulation of water between the atmosphere, land, and open water bodies.
Figure 2.3 Schematic cross section of aquifer types.
Figure 2.4 Streams may either discharge to ground water or be recharged by ground water.
Figure 2.5 Wells completed in alluvial deposits adjacent to streams or rivers will impact the surface water flows.
Figure 3.1 Seven water divisions have been created to administer the waters of the state.
Figure 3.2 The Colorado Ground Water Commission has established eight designated ground-water basins.
Figure 3.3 Schematic of typical domestic well completion and water supply system.
Figure 3.4 Principal sources of ground-water contamination.
Figure 4.1 Colorado ’s major Quaternary-age alluvial deposits.
Figure 4.2 Location and extent of the state’s major sedimentary rock aquifers and structural basins.
Figure 4.3 Major aquifer systems within the state’s mountainous regions.
Figure 4.4 Hydrogeologic units throughout Colorado.
Figure 5.1-1 Location of the South Platte River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.1-2 Saturated thickness of the lower South Platte River alluvium along the Front Range.
Figure 5.1-3 Water-table elevation contours for the lower South Platte River alluvial aquifer.
Figure 5.1-5 Concentrations of total dissolved solids in the lower South Platte River alluvial aquifer.
Figure 5.2-1 Location of the Arkansas River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.3-1 Location of the Colorado River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.4-1 Location of the Yampa River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.5-1 Location of the White River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.6-1 Location of the Gunnison River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.7-1 Location of the Republican/Arikaree River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.8-1 Location of the San Juan River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 5.9-1 Location of the Dolores River basin showing extent of mapped alluvium and distribution of alluvial wells.
Figure 6.1-1 Location of the Denver Basin (ground-water administration boundary).
Figure 6.1-2 Extent of confined and unconfined conditions within the Denver Basin aquifers.
Figure 6.1-3 General geologic cross sections through the Denver Basin.
Table 6.1.1 Hydrogeologic Units in the Denver Basin
Figure 6.1-4 Potentiometric surface of the Denver Basin aquifers, 1978.
Figure 6.1-5 Concentrations of total dissolved solids in the Denver Basin aquifers.
Figure 6.2-1 Location and extent of the Piceance Basin, showing the distribution of permitted water wells.
Table 6.2-1 Hydrogeologic Units of the Piceance Basin.
Figure 6.2-2 Histogram of reported well depths representing the 90 th percentile of wells of record.
Figure 6.3-1 Generalized structure map of the Eagle Basin area.

Figure 6.3-2

Location and extent of the Eagle Basin showing the distribution of permitted water wells.
Table 6.3.1 Hydrogeologic Units of the Eagle Basin.
Figure 6.3-3 Generalized geologic cross section through the Eagle Basin.
Figure 6.4-1 Location and extent of the Sand Wash Basin showing the distribution of permitted water wells.
Figure 6.4-2 Generalized geologic cross section through the Sand Wash Basin.
Table 6.4-1 Hydrogeologic Units of the Sand Wash Basin.
Figure 6.5-1 Location and extent of the Paradox Basin showing the distribution of permitted water wells.
Table 6.5-1 Hydrogeologic Units of the Paradox Basin.
Figure 6.5-2 Generalized geologic cross section through the Paradox Basin.
Figure 6.6-1 Location and extent of the San Juan Basin showing the distribution of permitted water wells.
Table 6.6-1 Hydrogeologic Units of the San Juan Basin.
Figure 6.7-1 Location and extent of the Raton Basin showing the distribution of permitted water wells.
Figure 6.7-2 Generalized geologic cross section through the southern Raton Basin.
Table 6.7-1 Hydrogeologic Units of the Raton Basin.
Figure 6.7.3 Water quality in the Cuchara-Poison Canyon aquifer, southern Raton Basin.
Figure 6.8-1 Location and extent of the Dakota-Cheyenne aquifer, outside of designated basins and the High Plains aquifer, showing the distribution of permitted water wells.
Table 6.8-1 Deeper Hydrogeologic Units in Eastern Colorado.
Figure 6.9-1 Location and extent of the High Plains aquifer from a regional perspective.
Figure 6.9-2 Water well distribution for the High Plains aquifer in Colorado.
Table 6.9-1 Hydrogeologic Units of the High Plains Aquifer.
Figure 6.9-3 Water level changes in the High Plains aquifer of Colorado.
Figure 7.1-1 Location and extent of the Rio Grande Basin showing distribution of mapped Quaternary alluvium and permitted water wells.
Figure 7.1-2 Generalized geologic cross section in the central part of the San Luis Valley.
Table 7.1-1 Hydrogeologic Units of the San Luis Valley.
Figure 7.1-3 Water-table elevation of the unconfined aquifer of the San Luis Valley, late 1996-early 1997.
Figure 7.2-1 Location and extent of the Wet Mountain Valley and Huerfano Park, showing the distribution of permitted water wells.
Figure 7.2-2 Generalized geologic cross section through Huerfano Park.
Table 7.2-1 Hydrogeologic Units of Wet Mountain Valley and Huerfano Park.
Figure 7.3-1 Distribution of reported well depths from the Division of Water Resources database.
Table 7.3-1 Location and extent of North and Middle Park Basins showing the distribution of permitted water wells.
Table 7.3-2 Hydrogeologic Units of North Park.
Figure 7.3-2 Hydrogeologic Units of Middle Park.
Figure 7.4-1 Location and extent of the South Park Basin showing the distribution of permitted water wells.
Figure 7.4-2 Generalized geologic cross section of the South Park region.
Table 7.4-1 Hydrogeologic Units of South Park Basin.
Figure 7.4-3 Distribution of well depths in the South Park Basin.
Figure 7.5-1 Location and extent of Precambrian crystalline rocks and the distribution of permitted water wells therein.
Figure 7.5-2 Location and extent of Tertiary igneous rocks and the distribution of permitted water wells therein.
Figure 7.5.3 Conceptual model of the aquifer system in fractured, crystalline rock.
Figure 7.5.4 Precambrian crystalline-rock water well depths and their relative frequency of occurrence.
Figure 7.5.5 Published range in hydraulic conductivity of volcanic rocks.