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E-Splash May 2012 - Lake Decatur Source Water Protection; Past, Present and Future
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Illinois Section AWWA - E-Splash -  May 2012

Lake Decatur Source Water Protection: Past, Present and Future
Keith Alexander, Source Water Protection Committee Member
Director of Water Management, City of Decatur

 Lake Decatur is a 2,816 acre reservoir constructed in 1920-1922 by the impounding of the Sangamon River, a tributary of the Illinois River. The watershed is 925 square miles, 85% of which is in crop production, including 500,000 acres of corn and soybean fields. There are two water treatment facilities withdrawing a combined daily average of 34 MGD from the lake. One facility is owned by the City of Decatur for drinking water and the other by the Archer Daniels Midland Company for industrial process water.

In early 1940s, while World War II raged on, Decatur established the Upper Sangamon Valley Conservation Service, employed 2 soil conservationists, and helped establish the Macon Co. Soil & Water Conservation District (SWCD). Other districts soon followed. By 1944 more than 200 farmers were installing best management practices (BMPs) on 18,000 acres in the Lake Decatur watershed.

A renewed effort for intensive Lake Decatur source water protection began in 1987 when Decatur and the Macon Co. SWCD entered into an annual watershed conservation and protection agreement. These have continued to the present day. Current Decatur funding for the Macon Co. SWCD includes: 1) a full time Watershed Specialist, full time Watershed Technician, and one third time Administrative Assistant, 2) watershed conservation protection and education programs, 3) BMP cost share program for design work and construction, and 4) NPDES Stormwater Phase II construction site compliance assistance.

By 1995 our watershed efforts were recognized as one of the top model projects to improve the Illinois River Valley by then Lt. Governor Bob Kustra. In 1997 the Heart of the Sangamon River Ecosystem Partnership (an IL Department of Natural Resources Conservation 2000 initiative) was formed. Accomplishments included a watershed resource inventory, comprehensive plan, and several IDNR grant awards. Partnership members continue to meet as the Lake Decatur watershed stakeholder committee.

Since the late 1990s numerous other watershed conservation and protection grants have been obtained from state and federal agencies such as the IEPA, IDNR, IDOA and USDA. Other key partners have included the University of Illinois, Illinois Farm Bureau, Illinois Fertilizer & Chemical Association, and many others. Since the watershed is so large, four sub watershed resource plans were created by Macon Co. SWCD staff, USDA Natural Resources Conservation Service staff, and stakeholder groups from each sub watershed. To assist with the implementation of the recommendations of these plans, Decatur contributed $300,000 toward the construction of best management practices in these drainage areas.

In 2003 the City began partnering with the Agricultural Watershed Institute, a Decatur based not-for-profit organization, to provide research and public education services in the Lake Decatur watershed including nutrient management, beneficial use of dredged sediment, water resources planning & management and biomass energy promotion.

The USDA NRCS Illinois Office awarded the Lake Decatur Watershed as "Watershed Planning Effort of the Year” in 2004. The Sangamon River/Lake Decatur Watershed TMDL Report was approved in 2007. Decatur recently participated in the Drought Ready Communities Project sponsored by National Drought Mitigation Center, IL State Water Survey and others. The Agricultural Watershed Institute recently completed a USEPA Targeted Watershed Program Grant that provided: 1) GIS-based software & precision agriculture technology to optimize nitrogen management on farm land, 2) drainage water management and subsurface bioreactors to reduce nitrate movement into surface waters, and 3) soil testing and variable rate technology to improve phosphorus management on farm land.

The Agricultural Watershed Institute is currently working on a multi-year Local Bioenergy Initiative to promote local/regional energy grass propagation and utilization for: 1) renewable energy and to reduce dependence on foreign energy, 2) improve wildlife habitat, soil conservation and water quality, 3) assist local farmers and landowners to begin growing energy grasses, 4) develop and demonstrate optimal locations to grow energy crops, and 5) develop markets for energy grass usage and related benefits such as economic diversity & economic enhancement.

An IEPA Section 604(b) Water Quality Management Planning Grant was recently awarded to the Agricultural Watershed Institute to perform the following tasks: 1) TMDL implementation plans for two sub watersheds in the Lake Decatur watershed, 2) considerable stakeholder involvement, 3) in depth resource inventories, 4) water quality modeling and cost estimates for a wide range of in-field, field-edge & riparian BMPs, 5) BMP scenario technical report, and 6) serve as a template for other watersheds to consider a suite of current and emerging BMPs effective at reducing nutrient loss from tile-drained cropland.

The Lake Decatur watershed is participating in the KIC (Keep It for the Crop) by 2025 Initiative recently established by the Illinois Council of Best Management Practices. This initiative emphasizes the 4Rs: the Right fertilizer source, at the Right rate, at the Right time, at the Right place. KIC by 2025 is initially focused on six IEPA identified priority watersheds to reduce nutrient loss, including the Lake Decatur Watershed.

What might the future hold for source water protection in agricultural watersheds? Possibilities include: 1) more field office consolidation of major players like the University of IL Extension, SWCD and USDA NRCS field offices, 2) continued tough competition for private, state and federal funds and grants, 3) doing the same or more work with less funding, 4) a statewide water quality standards for field tile discharges, and 5) a statewide fertilizer use penalty and reward system.

One issue seems certain - that society will continue to demand the highest quality drinking water and highest quality surface waters that we can politically agree to and collectively afford.

More information on Lake Decatur


Source Water

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Documents relating to source water issues that the Illinois Section AWWA Source Water Committee would like to share. If you have a document you would like added, please send it to
Item Name Posted By Date Posted
NLRS Biennial Report Summary.pdf PDF (1.23 MB)  more ] Administration 10/9/2017
Source Water Committee Members October 6, 2014 CSV (2.45 KB)  more ] Administration 10/6/2014
Source Water Committee Strategic Plan 2014 DOCX (34.58 KB)  more ] Administration 10/3/2014
Fracking Fact Sheet from WEF PDF (1.54 MB)  more ] Administration 11/5/2013
Regional Drought Condition Report PWS July 24 20 PDF (342.75 KB)  more ] Administration 8/5/2012
Lawn to Lake - save the date PDF (260.63 KB) Administration 3/13/2012
2012 Homeowners Association Workshop PDF (342.63 KB) Administration 3/13/2012


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SPLASH Media Kit_2018 PDF (1.8 MB) Administration 11/13/2017
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