Soil Moisture Lacking in Parts of Illinois, Illinois State Water Survey

Press Release

For Immediate Release August 8, 2001
Soil Moisture Lacking in Parts of Illinois

Source:   
Contact:   
Bob Scott, meteorologist - (217) 333-4966, Fax: (217) 333-1708, r-scott5@illinois.edu
Eva Kingston - (217) 244-7270, Fax: (217) 333-1708, eva@sws.uiuc.edu

"Water resources in Illinois are again reflecting dry conditions over parts of the state," according to meteorologist Bob Scott of the Illinois State Water Survey, a division of the Illinois Department of Natural Resources. The Water Survey's latest Illinois Soil Moisture Summary suggests that portions of central and northern Illinois are experiencing increased dryness throughout the top several feet of soil.

Dry conditions will probably have adverse effects on some agricultural interests in these areas. With the beginning of harvest just weeks away, time is running out for rainfall to help those crops where moisture has been insufficient. Hydrologically, though, the state is several months away from a point of concern as it will take reduced precipitation over a much longer period for severe impacts on groundwater and surface water.

"In an area north and east of a line from Champaign to Topeka (Mason County) to Freeport (Stephenson County), soil moisture measured at the end of July was just 25 to 50 percent of normal between the surface and 3.5 feet down. It was only marginally better down to 6 feet of depth, 50 to 75 percent of usual levels," continues Scott.

The primary cause of the dryness has been a reduction in the average rainfall for the area. Since the second week in June, rainfall totals in Illinois along and northwest of a line from Belleville to Kankakee have averaged between 65 and 75 percent of normal. This area, along with Wisconsin and much of the Great Lakes basin to the east, has been classified as "abnormally dry"--the lowest rank given by the National Oceanic and Atmospheric Administration Climate Prediction Center's drought assessment group. In essence, the natural source of moisture for soils in these areas has been insufficient to accommodate seasonal maximum water use by plants and evaporation.

However, the southern third of the state has reported rainfall totals averaging 10 to 25 percent above average. This has generated surpluses in soil moisture in parts of southern Illinois from 150 to 200 percent of normal levels.

"Fortunately, despite some short periods of hot conditions, temperature readings across the state during the same two-month period have been within a few degrees of average. Thus, just the agricultural sector has felt the impacts of low rainfall totals for the time being," says Scott.

"Typically, the influence of reduced precipitation on other water resources data occurs more slowly. For example, shallow groundwater levels in northern Illinois have begun to fall, but most are within a foot of their long-term normal level for the end of July. River and stream flows are below normal in central Illinois and mostly normal in northern Illinois. Central and southern Illinois public water-supply reservoirs are all within 2 feet of their target operating level for this time of year," continues Scott.

Regardless, tracking the potential impacts of the current dryness on other water resources is important. Furthermore, autumn and winter are the normal months when soils are recharged with the moisture needed for farming operations the following year. Official climatological outlooks issued by the Climate Prediction Center call for equal chances of above, below and average precipitation over the next one to three months.

"We need to keep a careful eye on Illinois precipitation totals during the next several months," concludes Scott.

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