High Plains States Groundwater Demonstration ProgramParts1&2

• Description: Part I - Overview, Results and Findings; Part II- Cooperative Sponsored Investigation
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/1/2000
• Author: U.S. Department of the Interior Bureau of Reclamation
• Title: High Plains States Groundwater Demonstration Program - Program Summary Report, Parts I & II
• Water Supply Pro - Doc Type: Report/Study

The High Plains Aquifer:
The High Plains Aquifer underlies 174,000 square miles in parts of Colorado, Kansas, Nebraska,
New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. About 20 percent of the irrigated land in
the United States is in the High Plains, and about 30 percent [40 percent in 1995] of the groundwater
used for irrigation in the United States is pumped from the High Plains Aquifer. During 1980, about
170,000 wells pumped 18 million acre -feet of water to irrigate nearly 14 million acres.
The High Plains Aquifer is a water table [unconfined] aquifer consisting mainly of near - surface sand and
gravel deposits of Tertiary and Quaternary age. The Tertiary Ogallala Formation, which underlies about
80 percent of the High Plains, is the principal geologic unit in the aquifer. The maximum saturated
thickness of the aquifer is about 1,000 feet and averages 200 feet. Groundwater generally flows
from west to east at an average rate of about 1 foot per day and discharges naturally to streams and
springs and by evapotranspiration in areas where the water table is near land surface. Precipitation is
the principal source of recharge to the aquifer. Recharge rates range from about 0.03 inch per year in
parts of Texas to 6 inches per year in areas of dune sand in Kansas and Nebraska.
About 3.25 billion acre -feet of drainable water is stored in the aquifer. Approximately 66 percent of
the water in storage is in Nebraska, and 12 percent is in Texas. New Mexico, the State with the smallest
water resource in the High Plains, has only 1.5 percent of the volume of water in storage.
Pumping has caused extensive areal water -level declines in the aquifer. Since irrigation began in the
High Plains, water levels have declined more than 10 feet in 50,000 square miles and more than 50 feet
in 12,000 square miles. Water level declines of as much as 200 feet have occurred since irrigation
started, and the volume of water in storage in the aquifer has decreased by 166 million acre -feet.
About 70 percent of the depletion has occurred in Kansas.
Source: Gutentag, et al., 1984 (emphasis added)
High Plains Aquifer Facts
States of the High Plains Aquifer
Characteristic
Total
CO
KS
NE
NM
OK
SD
TX
WY
Area underlain by aquifer
174,050
14,900
30,500
63,650
9,450
7,350
4,750
35,450
8,000
(Square Miles)
State percent of total
100
8.6
17.5
36.6
5.4
4.2
2.7
20.4
4.6
aquifer area (% )
Percent of State area
- - - - - --
14
38
83
8
11
7
13
8
underlain by aquifer ( %)
Average area weighted
190
79
101
342
51
130
207
110
182
saturated thickness in
1980 (feet)
Average area weighted
187
74
93
344
46
127
206
104
180
saturated thickness in
1996 (feet)
Volume of drainable
3,250
120
320
2,130
50
110
60
390
70
water in storage in
1980 (AF x 106)
Volume of drainable
3,202'
114`
296'
2,142'
45'
107'
59.8'
369'
69.2'
water in storage in
1996 (AF x 10')
'Data extrapolated from change in average area weighted saturated thickness - approximate only
Source: Dugan, et al., 1994; Weeks, et al., 1990; Gutentag, et al., 1984; and USGS Internet pages.
2.20 High Plains States Groundwater Demonstration Program