News Release, Kansas Geological Survey, March 23, 2009
LAWRENCE--Southwestern Kansas sustained accelerated declines in ground-water levels in 2008 while levels rose slightly in south-central counties, according to preliminary data compiled by the Kansas Geological Survey (KGS), based at the University of Kansas.
The Survey and the Kansas Department of Agriculture's Division of Water Resources (DWR) measured levels in approximately 1,400 water wells in 47 western and central Kansas counties in January as part of their annual assessment program.
As was the case in 2007, precipitation played an important role in the rise or fall of water levels.
"Southwest Kansas started off the 2008 growing season very dry, with most of the area receiving less then 25 percent of their normal precipitation levels," said Brownie Wilson, the Survey's water-data manager. "Normal precipitation didn't return until around August through October when it was much too late. Unfortunately, we have seen the same dry pattern so far this year."
In 2008 water levels in southwest Kansas fell an average of 2.85 feet, with many areas seeing declines of more than 5 feet. This followed drops of 1.72 feet in 2007 and 2.09 feet in 2006. Since 1996, when annual measurements were first taken by the KGS, levels in the region have risen only one time--0.10 feet in 1998.
About 80% of the state's 39,000 wells are located in the region underlain by the High Plains aquifer, the main source of water in western Kansas. Declines in the Ogallala portion of the High Plains aquifer were greatest in the southwestern counties, particularly the counties centered around Grant and Haskell counties where dry conditions have been most severe.
With less precipitation, more ground water is withdrawn for irrigation, which in the short run, affects the water level more than the lack of recharge to the aquifer, Wilson said.
Farther north in western Kansas, where precipitation was closer to normal, 2008 declines were smaller. In northwest--Cheyenne to Trego counties--and west-central Kansas--Wallace to Lane counties--the water level average dropped 0.10 and 0.21 feet, respectively.
In south-central Kansas, average ground-water levels rose in 2008, although at a slower pace than in 2007 when some areas received record precipitation as much as 200 percent above normal.
"In 2008 south-central Kansas experienced normal to well above normal precipitation patterns over the growing season, particularly in May," Wilson said.
Water levels in the Great Bend Prairie aquifer--covering Pratt and Stafford counties and parts of several surrounding counties--rose an average of 0.55 feet in 2008. In the Equus Beds aquifer that extend north and west of Wichita, levels rose an average of 1.79 feet with some areas rising more than 3 feet.
In 2007 water levels had risen 3.1 feet in the Great Bend Prairie aquifer and 2.04 feet in the Equus Beds. In 2006 both had declined.
Overall in the 47-county network the average level fell 0.80 feet, with gains in the eastern section of the network being offset by losses in the west.
Ground-water levels are not monitored in eastern Kansas, which receives greater precipitation and is supplied mainly by surface water from rivers and reservoirs.
Results of the measurements are provisional and subject to revision based on additional analysis. The measurement data is available at http://www.kgs.ku.edu/Magellan/WaterLevels/index.html.