Correlation between the Soil Gas Survey and Groundwater D a t e Areas 1-5 ..... NOTE: All exhibits contained in the text (except Exhibits 2-1 and 6-2) are text tables; all data tables are located in Section 11.0 beginning on page 59 .

Situated in two major physiographic provinces, the Appalachian Plateaus and the Central Lowland, the basin includes varied topographic and geomorphic features that affect the hydrology. As of 1990, the basin was inhabited by approximately 10.4 million people. Lake effect has a large influence on the temperature and precipitation of the basin, especially along the leeward southeast shore of Lake Erie. Mean annual precipitation generally increases from west to east, ranging from 31.8 inches at Detroit, Mich., to 43.8 inches at Erie, Pa. The rocks that underlie the Lake Erie-Lake St. Clair Basin range in age from Cambrian through Pennsylvanian, but only Silurian through Pennsylvanian rocks are part of the shallow groundwater flow system. The position of the basin on the edge of the Michigan and Appalachian Basins is responsible for the large range in geologic time of the exposed rocks. Rock types range from shales, siltstones, and mudstones to coarse-grained sandstones and conglomerates. Carbonate rocks consisting of limestones, dolomites, and calcareous shales also underlie the basin. All the basin is overlain by Pleistocene deposits till, fine-grained stratified sediments, and coarse-grained stratified sediments most of Wisconsinan age. A system of buried river valleys filled with various lacustrine, alluvial, and coarse glacial deposits is present in the basin. The soils of the Lake Erie-Lake St. Clair Basin consist of two dominant soil orders: Alfisols and Inceptisols. Four other soil orders in the basin (Mollisols, Histisols, Entisols, and Spodosols) are of minor significance, making up less than 8 percent of the total area. The estimated water use for the Lake Erie-Lake St. Clair Basin for 1990 was 10,649 Mgal/d (million gallons per day). Power generation accounted for about 77 percent of total water withdrawals for the basin, whereas agriculture accounted for the least water-use withdrawals, at an estimated 38 Mgal/d. About 98 percent of the total water used in the basin was drawn from surface water; the remaining 2 percent was from ground water. Agricultural and urban land are the predominant land covers in the basin. Agriculture makes up approximately 74.7 percent of the total basin area; urban land use accounts for 11.2 percent; forested areas constitute 10.5 percent; and water, wetlands, rangeland, and barren land constitute less than 4.0 percent. The eight principal streams in the basin are the Clinton, Huron, and Raisin Rivers in Michigan, the Maumee, Sandusky, Cuyahoga, and Grand Rivers in Ohio, and Cattaraugus Creek in New York. The Maumee River, the largest stream in the basin, drains 6,609 mi2 and discharges just under 24 percent of the streamflow from the basin into Lake Erie. Combined, the eight principal streams discharge approximately 54 percent of the surface water from the basin to the Lake Erie system per year. Average runoff increases from west to east in the basin. The glacial and recent deposits comprise the unconsolidated aquifers and confining units within the basin. Yields of wells comp...

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