RECENT HYDROCLIMATIC FLUCTUATIONS AND THEIR EFFECTS ON WATER-RESOURCES IN ILLINOIS

Two contrasting 18 yr periods (1950-1967 and 1968-1985) were compared to illustrate the hydrologic and water resources effects of a change to a wetter climatic regime over Illinois. For the nine State Climate Divisions, precipitation increases and fluctuations in wetness measured by Palmer Drought Indices revealed a marked shift between the periods. The seasonal variability and spatial coherence of this precipitation climate fluctuation and its impacts are examined in detail and quantitative relationships are derived between Drought Indices and measured soil moisture and streamflow at several sites. Riverflow and well level changes are consistent with this climate change on the 20-40 yr time-scale which has had some significance for water management in the area.