The Use of Hydrologic and Ecological Models to Guide Restoration Efforts

The Illinois River has been significantly altered physically and hydrologically over the last century, resulting in a degraded ecosystem. One of the major changes was the construction of levees in the floodplain to protect agricultural levee and drainage districts (LDDs) from regular flooding from the river. A total of 24 LDDs were established in the lower Illinois River between 1987 and 1916. Removal of a large part of the river's floodplain contributed to more rapid water-level fluctuations during the growing season that inhibit establishment of native vegetation along the river. Major ecological restoration efforts are underway in the Illinois River basin. One of the goals of those restoration efforts is to re-establish the natural hydrology of the river and its floodplain to the extent possible without disrupting economic activities along the river. One of the options under consideration is the reconnection of some of the floodplain with the river. Hydrologic and ecological models are being used to assess restoration potential and to guide restoration efforts along the river. Water budget and unsteady flow models of the Illinois River are being used to evaluate water level fluctuations within the LDD. Modeling results are then used as input to a vegetation model that simulates plant growth based on water depth, fluctuation, and duration. This paper presents research results for a selected segment of the Illinois River.