Shallow groundwater levels in Illinois remain below average. The latest water level data we have for ISWS shallow observation wells at Fermi National Laboratory (DuPage County) and Bondville (Champaign County) are at their lowest levels for August since their records started in November1988 and March 1982, respectively. The water level at Fermi Lab is 10.05' (1.97' below normal) and at Bondville is 7.37' (1.96' below normal). Water levels in both wells have fallen almost 0.9' since last being measured in late July. The Groundwater Information Office continues to receive reports from well drillers lowering pumps or redrilling wells to greater depths as a result of lowered water levels in aquifers in northern and northwestern Illinois, including Kane (Campton Township), LaSalle, and Whiteside Counties.
Irrigation demand appears to have decreased during the past two weeks along the border of Bureau and Whiteside Counties. Groundwater levels observed by the ISWS on August 3, 2005 have risen by 1 to 4 feet in the buried Sankoty aquifer, the aquifer favored by irrigators in this region of Illinois. By contrast, groundwater levels in observation wells completed in the surficial Tampico aquifer (overlying the Sankoty) declined about 3 to 4 inches in Whiteside, Lee, Bureau, and northern Henry counties. Historical records suggest that this trend will continue, possibly until December, despite the lessening of irrigation demand.
Although rainfall received across Illinois this past week may alleviate some soil moisture deficits, shallow groundwater levels can be expected to continue to decline until soil moisture is replenished, thus allowing water to infiltrate beyond the root zone of transpiring plants.