Dakota Home Report Archive FY92 Ann Rep

Kansas Geological Survey, Open-File Rept. 93-1
Annual Report, FY92--Page 7 of 20


Effect of River Valleys..., continued

Regional Setting

The vertical profile that is the subject of this report extends from the Baca-Las Animas county line in southeastern Colorado to western Lincoln County in central Kansas (Figure 16). The vertical profile is parallel to a flow line in the Dakota aquifer. It traverses portions of Baca and Prowers counties in Colorado and Hamilton, Kearny, Wichita, Scott, Gove, Trego, Ellis, Russell, and Lincoln counties in Kansas.

Figure 16--Location of the vertical profile in southeastern Colorado and western and central Kansas.

Physiography

Southeastern Colorado and southwestern and central Kansas are located in the Raton Section, Colorado Piedmont, High Plains, and Plains Border sections of the Great Plains physiographic province (Fenneman, 1946). The land surface slopes to the east and decreases in elevation from slightly more than 5,000 ft (1,500 m) near the Baca-Las Animas County line, Colorado, to slightly more than 1,400 ft (430 m) in western Lincoln County, Kansas (Figure 17). The regional land-surface slope ranges from 26.7 ft/mi (5.06 m/km) in southeastern Colorado to 10.6 ft/mi (2.01 m/km) in western Kansas to 6.7 ft/mi (1.3 m/km) in central Kansas in the vertical profile. The vertical profile traverses the Arkansas, Smoky Hill, and Saline River drainage basins (Figure 18). The valleys cut by these river systems into unconsolidated Cenozoic deposits and Cretaceous bedrock locally increase the topographic relief significantly. In the Arkansas River valley in southeastern Colorado and southwestern Kansas and in the Saline River valley in central Kansas the local relief commonly exceeds 200 ft/mi (37.9 m/km).

Figure 17--Generalized land-surface topography and the major streams traverses by the vertical profile in eastern Colorado and western and central Kansas and adjacent areas.

Figure 18--Major structural features of eastern Colorado and western and central Kansas and adjacent areas reflected in Precambrian and younger rocks.

Climate

The climate of the region is warm, continental semiarid in all except the eastern portions of the study area in central Kansas, where the climate is subhumid continental (Dugan and Peckanpaugh, 1985). The mean annual temperature is approximately 54 degrees F across the study area. Mean annual rainfall for the period 1951-1980 ranges from 15 in. (38 cm) in southeastern Colorado to 28.5 in. (72.4 cm) in central Kansas. Approximately 75% of the precipitation falls mainly during the warm season months of the year. Because of the low relative humidity, high average wind velocities, and abundant sunshine, the potential evaporation exceeds the average annual precipitation over most of the region. Dugan and Peckanpaugh (1985) calculated that the potential mean annual recharge to ground water from precipitation ranges from less than 0.1 in. (0.2 cm) in southeastern Colorado to 1-2 in. (5 cm) in central Kansas.

Geologic Structure

An understanding of the geologic structure is useful for delineating zones where tectonic activity or local subsidence from salt dissolution may have created vertical pathways for fluid transmission between aquifer units (Zeller et al., 1976; Bredehoeft et al., 1983; Kolm and Peter, 1984). In Kansas and in much of the Great Plains region, movement along these structures in response to changing stress fields has been episodic since the Precambrian Era (Merriam, 1963; Berendsen and Blair, 1986). Figure 18 shows the location of geologic structures referred to in this report.
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Kansas Geological Survey, Dakota Project
Updated Jan. 1997
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