The Tri-County region, consisting of Clinton, Eaton, and Ingham Counties, is an area of 1,697 square miles in Michigan's Lower Peninsula and has as its hub the Lansing metropolitan area. The land surface ranges in altitude from about 700 to about 1,000 feet. The region receives an average of about 31 inches of precipitation each year.

The population is nearing 400,000 and by 1990 will be near 600,000. Average daily water use is slightly more than 30 million gallons today; by 1980 it will be about 50 million gallons, and by 1990 it will probably be about 70 million gallons.

The Tri-County region is drained by seven river systems. The median annual 7 -day mean low flows of the principal streams in these systems were measured at the point farthest downstream within the region. These values, in cubic feet per second, are as follows: Grand River, 180; Maple River, 34; Looking Glass River, 28; Red Cedar River, 30; Portage Creek, 15; Battle Creek, 20; and Thornapple River, 24-a total of 331 cubic feet per second or about 220 million gallons per day. The areal variance in 7-day low-flow runoff ranges from 0 to 0.15 cubic foot per second per square mile.

The principal source of ground water in the Tri-County region is a complex aquifer system composed of the Saginaw and Grand River Formations and some of the overlying glacial sediments. This aquifer yields between 300 and 700 gallons per minute to individual wells in much of the western half of Ingham County, in the eastern half of Clinton County, in a small area in southeastern Clinton County, and in northeastern Eaton County. In some parts of the region, the glacial sediments are favorable for development of moderate to large supplies of water. Minor aquifers in the region are the Bayport, Michigan, and Marshall Formations.

Providing water supplies in the future requires complete and comprehensive water-management programs. Such management programs involve determining which of several alternative water-development systems is the best. Some of the chief factors and methods that must be considered when planning these systems are combined use of ground and surface water, artificial recharge, treatment of wastes, use of storage reservoirs, and importation of water from the Great Lakes.