Sediment Dynamics and the Hydromorphology of Fluvial Systems (Proceedings of a symposium held in Dundee, UK, July 2006). IAHS Publ. 306, 2006. 295 Evaluating the effectiveness of the Illinois River Conservation Reserve Enhancement Program in reducing sediment delivery MISGANAW DEMISSIE, LAURA KEEFER, JIM SLOWIKOWSKI & KIP STEVENSON Center for Watershed Science, Illinois State Water Survey, 2204 Griffith Drive, Champaign, Illinois 61820, USA demissie@uiuc.edu Abstract The ecology of the Illinois River, a tributary of the Mississippi River, was severely degraded for several decades due to sedimentation and water-quality problems. A joint federal/state program known as the Illinois River Conservation Reserve Enhancement Program (CREP) was initiated in 1998 to restore the river. One of the major goals of the program is to reduce sediment delivery to the river by 20 percent. To assess the program’s progress toward meeting that goal, the State of Illinois is developing a scientific process that includes data collection, modelling and evaluation. The baseline condition for sediment delivery was prepared based on available data collected in 1981– 2000. Using that information as a baseline, it will be possible to assess and compare sediment delivery and sedimentation in the Illinois River valley for different periods after CREP implementation. Key words conservation reserve; enhancement; Illinois River; land use; monitoring; sediment delivery; sediment load; Illinois, USA INTRODUCTION The Illinois River is one of the major tributaries of the Mississippi River that drains 40 percent of the State of Illinois and parts of Indiana and Wisconsin, USA (Fig 1). There was severe degradation of the river ecology for several decades due to sediment- tation and water-quality problems. Currently, there are various initiatives to restore the river and its watershed. The Illinois River Conservation Reserve Enhancement Program (CREP) is a joint federal/state program to improve water quality and wildlife habitat in the Illinois River basin by protecting and restoring the flood plain corridor of the Illinois River and its tributary streams. The program was initiated in 1998 through a Memorandum of Agreement (MOA) between the US Department of Agriculture, the Commodity Credit Corporation, and the State of Illinois. Enrolment in the program began on 1 May 1998. The MOA was amended and re-authorized several times to increase acreage eligible for enrolment up to 93 890 ha (232 000 acres). From 1998 to 2004, a total of 44 863 ha (110 854 acres) enrolled in the program. A subset of that total, 29 592 ha (73 121 acres) is also enrolled in the state option for permanent easement (92%), 15-year easement contract extension (5%), and 35-year easement contract extension (3%) (State of Illinois, IDNR, 2005). Two of the four specific goals established for the program were: – Reduce the amount of silt and sedimentation entering the mainstem of the Illinois River by 20%.