Oakland County, an area of 899 square miles, is in southeastern Michigan. The southern part of the county is overlapped by the suburbs of the city of Detroit.
In 1970, about 850,000 people were living in the county and using about 100 million gallons of water a day. More than 80 percent of the water used for large industrial and municipal supplies came from Detroit's water system.
The average annual rate of streamflow from the county is about 370 million gallons per day (575 cubic feet per second). Median annual 7-day low flows range from 0 to 0.25 cfs per square mile. Low flows can be augmented by more than 60,000 acre-feet of water captured during high streamflow by construction of small reservoirs at 21 inventoried sites.
Glacial deposits and the Marshall Sandstone are the prime sources of ground water. Most wells that penetrate the full thickness of glacial deposits in the northwestern part of the county will yield at least 50 gpm (gallons per minute), and many will yield more than 400 gpm. The Marshall Sandstone, which occurs only in the Holly area, is capable of yielding more than 1,000 gpm.
The chemical quality of both surface and ground water is relatively good throughout the county. Only in the southern part of the county is the dissolved solids above the acceptable standard of 500 milligrams per liter.
