Bathymetry (Water Depth) 75% Exceeded Discharge: Illinois River

Bed elevation data exists as topobathy data for the Upper Mississippi River System (UMRS) through the US Army Corps of Engineers (USACE), Upper Mississippi River Restoration (UMRR) program. While those data meet some needs, water depth is often the desired information needed by researchers and resource managers. Water depth data (i.e., bathymetry) at specific discharge conditions can be derived by construction of a water surface elevation GIS data layer. Such a layer was developed using liner interpolation between gages and adjusting for lateral discontinuity. The selected discharge condition was a low water condition determined by the condition exceeded 75% of the time over a 40-yr period.