Iowa Alluvial Aquifer

Iowa Alluvial Aquifers

Iowa Alluvial Aquifers

Science Center Objects

This study is part of ongoing research in Iowa to investigate the availability (quantity and quality) of water in alluvial aquifers that are used for agricultural, domestic, municipal, and industrial supplies. Previous research included modeling and delineation of ground water flow in the Mississippi River, Des Moines River, iowa, and Cedar River alluvial aquifers. The water quality of these and other alluvial aquifers in Iowa also have been studied.

Ground water flow

The Mississippi River Alluvial aquifer in Muscatine County Iowa is heavily used as a source of industrial, municipal, and agricultural supply. Norton and others (1912) first described the installation of alluvial wells for the city of Muscatine. Hydrologic properties and chemical characteristics of the aquifer were described by Hansen and Steinhilber (1977). A steady-state, ground-water model indicated that drawdown in the lower alluvium caused by the pumping centers in Iowa extends beneath the Muscatine Slough in the northwest part of the study area and beneath the Mississippi River in the central and northern parts of the area (Lucey and others, 1995) . The primary sources of ground water in the alluvium are recharge from precipitation, leakage from the Mississippi River, and infiltration of upland runoff. The bedrock is not a major contributor of ground water to the alluvium. Hypothetical model pumping scenarios indicates that pumping causes simulated drawdown that varies from about 10 ft to greater than 50 ft relative to 1993
conditions (Lucey, 1997). Increased pumping could affect long-term water quality and hydrology in the Muscatine area (Lucey, 1997). The Lucey and others (1995) model was modified to delineate sources of water to the Mississippi River alluvial aquifer near Muscatine, IA (Savoca and others, 2002) . The model indicated that primary sources of inflow to the aquifer are recharge through infiltration of precipitation and upland runoff (53 percent) and Mississippi River leakage (41 percent) and that the average traveltime of water from recharge to discharge at the municipal well fields was 13.6 years.

The flow system of the Mississippi River Alluvial Aquifer near Burlington, IA was modeled to identify sources of water and to assess effects of additional hypothetical withdrawls (Boyd, 2001). The primary sources of ground water to the alluvium were recharge from precipitation, subsurface flow from Flint River streamchannel deposits adjacent to the alluvium, and Mississippi River leakage.

Water Quality

NAWQA water quality (Savoca and others, 2000) WRI 99-4246 GW in agricultural and urban areas of alluvial aquifer. The greatest concentrations of nitrate and herbicides were found in the shallowest parts of the Iowa River alluvial aquifer (Detroy and Kuzniar, 1988: Kalkhoff and others, 1992). Median nitrate concentrations ranged from 16 mg/l near the top to less than 0.10 mg/L near the bottom of a 10 foot thick small headwaters stream alluvial aquifer (Kalkhoff and Schaap, 1996) in northeast Iowa. Movement of
contaminants from land surface was dependent on precipitation with nitrate and pesticides being detected in the in the aquifer within six weeks of chemical application (Detroy and Kuzniar, 1988).

The detection rate and concentration of metolachlor and atrazine in alluvial aquifers were consistent with their patterns of chemical use and/or application rates (Kolpin and others, 1997a). Herbicide compounds were detected in the alluvial aquifer more often than any other aquifer used for municipal water supply in Iowa (Kolpin and others, 1997b).