Release date Internet location of release September 1, 2000 http://wy.water.usgs.gov/news/html/090100b.htm Contact Address District Chief 2617 E. Lincolnway, Ste. B Ground-Water Specialist Cheyenne, WY 82001-5662 Public Information Officer E-mail Phone Fax state_rep_wy@usgs.gov (307)778-2931 (307)778-2764
Ground-water levels continue to drop in monitor wells in southeast Wyoming in response to drought conditions. The drop in water levels is a combined effect of both lower precipitation and increased pumping from the aquifer. These are common effects to observe during a drought. The lack of precipitation limits the recharge to an aquifer and hot, dry conditions result in increased withdrawals as irrigators, public supplies and private well users pump more water.
Water levels in a monitor well southwest of Carpenter, Laramie County (fig. 1) show the effects of the drought. The well is completed at a depth of 110 feet below land surface in the Brule Formation, a member of the White River Group (Oligocene). Three changes can be observed by examining the water levels from the well -- water levels in 2000 as compared to 1999, seasonal trends, and long-term trends. Each change is examined individually below.
Figure 1. Laramie County map with well location shown.
Drawdown at this well this year reflects the same general drawdown pattern observed in 1999 with two notable differences (fig. 2). First, the drawdown started about a month earlier. The most likely reason for this is the lack of spring moisture, which resulted in the need to irrigate earlier in the year. Second, the rate of drawdown is steeper this year than last year. This probably reflects an increased amount of water being used due to the continuing drought conditions.
Figure 2. Hydrograph for 1999 and 2000.
Water levels in the well indicate aquifer drawdowns that occur as a result of seasonal irrigation. This annual drop in water levels corresponds to the start of irrigation season in April-May timeframe and continues until late summer (fig. 3).Water levels then recover until pumping starts again the next spring. Maximum drawdown generally occurs by mid-July.
Figure 3. Hydrograph for period of record.
The well has been monitored since 1973. The highest water level recorded was 14.12 feet below land surface on May 1-2 of 1974 and the lowest water level recorded was 46.86 feet below land surface on September 10, 1978. Water levels in the well showed a general downward trend from 1975 to 1979 (fig.3). During the period between 1980 and 1985 the trend in water levels was upward and since 1994 the trend has been fairly level. Water levels from the monitor well are collected and published as part of a cooperative project between the Wyoming State Engineer's Office and the U S Geological Survey.
Additional information can be found by accessing the Water Resources of Wyoming on the World Wide Web at: http://wy.water.usgs.gov/
Or contact:
USGS Wyoming State Representative
2617 E. Lincolnway, Suite B Cheyenne, WY
82001-5662
Phone: (307) 778-2931
FAX: (307) 778-2764
Email: state_rep_wy@usgs.gov
The URL for this page is: http://wy.water.usgs.gov/news/html/090100b.htm
U.S. Department of the Interior, U.S. Geological Survey
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