PROJ02181

• Contract/PO #: FS0014X
• Contractor Name: Southern High Plains Ground Water Management DistrictSouthern High Plains Ground Water Management Di
• Contract Type: Loan
• Water District: 0
• County: Baca
• County: Prowers
• County: Las Animas
• Loan Projects - Doc Type: Report

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1.0 SUMMARY

1. This report presents the findings of a geology and water resources study of the
Southern High Plains Ground Water Basin (Basin) on behalf of the Southern
High Plains Ground Water Management District (District). The Basin is located in
southeastern Colorado, south of the Arkansas River Basin in southeastern Baca,
Prowers and Las Animas counties. The investigation involved: (a) review of
previous investigations; (b) examination of water well records available at the
State Engineer's Office; (c) assessment of geologic and hydrogeologic
conditions; (d) evaluation of historical water-level changes and adequacy of
monitor well distribution; (e) evaluation of Landsat imagery to quantify irrigated
areas; (f) investigation of abandoned well records; and (g) confirmation of water
use in District.

2. Available geologic and hydrogeologic information indicates there are three major
aquifers in the District: (a) High Plains; (b) Dakota; and (c) Dockum; which range
in age from Quaternary to Triassic. The High Plains aquifer is comprised of
Quaternary age alluvium and eolian sands and Tertiary age sands and gravels of
the Ogallala Formation. The Dakota aquifer is comprised of the Cretaceous age
Dakota Sandstone, Kiowa Shale, and Cheyenne Sandstone. The Dockum
aquifer is comprised of sandstones and siltstones of the Triassic age Dockum
Group. The High Plains aquifer blankets most of the District. However, today
only small portions of the aquifer (primarily in the southeast comer of the District
and small isolated areas in the west-central and northeastern portions of the
District) still contain recoverable ground water. The Dakota aquifer underlies
most of the District except the southeast corner where the High Plains aquifer
lies directly over the Dockum aquifer. The areal extent of the Dockum aquifer is
not well known in the District because of the general lack of wells and the greater
depth of the Dockum than the other two aquifers.

3. In 1999, about 128,500 acres of land were irrigated within the Basin. The total
ground water pumped for irrigation was approximately 220,000 acre-feet.

4. Generally, ground-water levels in the Basin have dropped approximately 100 feet
over the last 50 years. Between 1999 and 2000, in irrigated areas, the ground-
water levels in the High Plains/Dakota or the High Plains/Dockum systems have
declined between 0.6 and 2.0 feet per year depending upon proximity to heavy
irrigation, recharge, and the source aquifer systems. In the developed aquifers,