Originating upstream from Indian Lake, the Great Miami River flows 170 miles southwest to its confluence with the Ohio River west of Cincinnati. The Great Miami River Watershed drains all or parts of 15 counties and also includes the Stillwater and Mad rivers and Twin, Wolf and Seven Mile creeks. The total drainage area of the watershed in Ohio is 3,946 square miles; the entire watershed, including the Whitewater River in Indiana, drains 5,702 square miles.
Land Use
More than 80 percent of the land is used for agriculture, primarily row-crop production of corn, soybeans and wheat. Residential, commercial and industrial uses cover about 12 percent of the watershed; forests cover about 4 percent; and water bodies or wetlands cover about 1 percent.
The watershed has a population of 1.3 million people with more than 75 percent of the population residing in urban areas. According to the U.S. Census Bureau 2004 population estimates, Dayton is the largest city in the watershed with 160,000 people. Other major cities within the MCD flood-protection system exceeding 50,000 people include Hamilton and Middletown. Cities with more than 20,000 people include Piqua, Troy and Fairfield. Each of these major population centers is located adjacent to one of the rivers or streams in the watershed.
Surface Water Quality
There are more than 6,600 miles of rivers and streams in the Great Miami River Watershed. Since the Clean Water Act was passed in 1972, regulations have limited the discharge of pollutants into waterways, so the water quality in the watershed has shown strong improvement.
These healthy waterways, in addition to the existence of several major lakes, provide many opportunities for water-based recreation. The cold-water habitat of the Mad River provides one of the few trout fishing streams in Ohio, and the scenic beauty of the Stillwater River attracts fishermen from all over the country. Boating, swimming and fishing are a few of the many activities enjoyed on Acton Lake, Indian Lake and Lake Loramie.
More than 40 percent of streams and rivers, however, still do not meet Ohio’s water quality standards. You can download fact sheets called “infographics” on each of the major subwatersheds of the Great Miami River to discover more about the health of, and threats to, surface water.
Groundwater
An estimated 97 percent of the population in the Great Miami River Watershed relies on groundwaterfor its drinking water supply. As a result of the watershed’s glacial deposits, the Great Miami River and many of its tributaries flow over a buried valley aquifer consisting of thick deposits of sand, gravel, cobble and boulders. According to a report produced in partnership with MCD, such porous material allows some wells to produce up to 3,000 gallons per minute.
Geology and Soils
The geology of the watershed consists of clay and silt-rich glacial sediments that lie on top of Ordovician- and Silurian-age bedrock. The Ordovician bedrock is comprised of limestone and shale, while the Silurian bedrock is predominantly limestone and dolomite. The dominant soils in this watershed are productive for agricultural purposes, being part of the Indiana and Ohio Till Plain Region.
