Illinois Drought Update
State Water Plan Task Force Meeting - June 21, 2005
Illinois State Water Survey, Department of Natural Resources
With little or no rain anticipated in the next 10 days, the period from March to June 2005 is expected to be the third driest March-June period in Illinois since 1895. Precipitation amounts across Illinois over the last 4 months are in the range of 5.7 to 7.6 inches below normal, or 45-60 percent of normal for most of the State. This corresponds to the category of “moderate drought” as defined by Changnon for a 3-month drought.
• Soil moisture is variable throughout the State, but on average is more than 2 inches below normal in the top 40 inches. The Illinois Agricultural Statistics Service lists only 26% of the top soil moisture as being adequate, with 45% short and 29% very short on moisture.
• The Illinois Agricultural Statistics Service lists 15% of the corn and soybean crop having poor to very poor conditions. Although crop stress this early in the season does not necessarily lead to poor yields, continued stress into July could have significant impacts.
• Rains last week had a temporary beneficial impact on streamflow levels, but flows are now receding quickly. With little additional rain expected for June, over 25% of the State will have total June flows in the much-below-normal range (lowest 10 percent on record).
• Most water supply reservoirs are near normal pool, but have started dropping earlier in the summer than is normal. Recent rains were centered in regions that have historically had water supply reservoir concerns. These rains have also brought Lake Shelbyville and Carlyle Lake up to within 0.5 foot of their summer target levels.
• The level of Lake Michigan has not changed since mid-May. In most years, Lake Michigan would be expected to continue rising into August.
• Shallow groundwater levels have been dropping consistently since February.
• Peak water use since the beginning of June has been very high, more typical of water use that we experience during the warmest periods in July and August. Rains last week had only a temporary effect in lowering water use.
We are now into summer and there is no significant rainfall in the forecast. Although water supply and agricultural impacts are not yet acute, we can expect additional deterioration of water conditions over the next few weeks, delving us further into drought status. We recommend that the Drought Response Task Force be convened.
The Water Survey has a new drought web site that will be updated each Wednesday for the duration of drought conditions (http://www.sws.uiuc.edu/hilites/drought/).