Water Supply Planning: American Bottoms Assessment of Water Resources for Water Supply

Abstract

Located adjacent to the Mississippi River and immediately east of St. Louis, MO, the American Bottoms Water Supply Planning Region (WSPR) envelopes portions of Madison, St. Clair, and Monroe counties (Figure 1). The Illinois Department of Natural Resources Office of Water Resources (IDNR-OWR) funds the Illinois State Water Survey (ISWS) to analyze water resources and sustainability in WSPRs throughout the state The Water Supply Planning initiative funded by IDNR-OWR is intended to promote discussions and management solutions for long-term sustainability of the state’s water resources. The following report discusses water resources and water usage in the American Bottoms WSPR. With the broad foundation provided by this report, we hope that informed regional stakeholders may help direct research into local water resource sustainability. The American Bottoms, occasionally referred to as the American Bottom, constitute the floodplain of the Mississippi River between Grafton, IL—where the Illinois River merges with the Mississippi River—and the northern vicinity of Chester, IL—where the Kaskaskia River converges with the Mississippi River. The eastern boundary of the floodplain is an 80-mile bluff that extends 200 to 300 feet above the floodplain. The American Bottoms WSPR consists of two anecdotal subregions: (1) the limestone uplands to the east, and (2) the ancestral Mississippi River floodplain (Figure 2). Important regional municipal centers include Alton, Wood River, Edwardsville, Collinsville, Granite City, East St. Louis, and Cahokia Heights (Figure 2). Many of the listed notable regional centers reside in the ancestral Mississippi River’s floodplain, where during the early 20th century the surficial glacio-alluvial aquifer provided an ample supply of high-quality groundwater. Also, several important interstate highways (I-55, I-64, and I-70) all converge in this WSPR, so maintaining healthy interstate commerce (i.e., managing stormwater runoff flooding) is an important regional concern. The influence of the ancestral and modern Mississippi River is evident throughout the American Bottoms WSPR. The Mississippi River is responsible for eroding, depositing, and creating the alluvial floodplain aquifer. Also, the paths of the ancestral Mississippi River are exhibited in the numerous surface water bodies that dot the floodplain, including Horseshoe Lake, an ancient river meander that has become an oxbow lake in the region. Furthermore, the water from the Mississippi River has promoted human settlement in the region throughout prehistory and today. Historically, the American Bottoms’ Mississippi River floodplain was home to one of the largest indigenous civilizations north of Mexico on the North American continent (Brown, 2004). Their influence and archaeological footprint can be witnessed at the Cahokia Mounds State Park, a UNESCO World Heritage Site (UNESCO World Heritage Centre, 2024), that is to the southeast of Horseshoe Lake near the center of the Mississippi River floodplain of the American Bottoms.Grant Code D497