NWS-ILX Rivers and Hydrology - Offers Advanced Hydrologic Prediction Services (AHPS) for Illinois river and river basin areas, including tabular, graphic and flood stage data. - http://www.crh.noaa.gov/ahps2/index.php?wfo=ilx
Lower Illinois River Basin NAWQA - Areas covered include the Illinois River and tributaries from Ottawa, Illinois, to the confluence with the Mississippi at Grafton, Illinois. - http://il.water.usgs.gov/proj/lirb/