Municipal water-supply systems in the central Lower Peninsula of Michigan were categorized into four regions on the basis of source of water for 1987. These categories included water systems that obtained water from aquifers in glacial drift, bedrock, or both, as well as those that obtained water from surface-water sources. Data on ground-water development were collected for 182 municipal water-supply systems for the period 1870-1987. Of the 182 systems, 135 used ground water for supply. Wells in glacial-drift aquifers supplied water for 60 municipalities; wells in bedrock aquifers supplied 58 municipalities. Combinations of wells in bedrock and glacial-drift aquifers supplied 17 municipalities. Surface-water sources supplied 45 municipalities; two municipalities used surface water and ground water. Of the 182 municipal systems, withdrawal data were available for only 145. Withdrawal data were collected for the period 1903-1985. Analysis of annual ground-water withdrawal data for the 145 municipal water-supply systems indicates that average annual per capita municipal ground-water withdrawal ranged from 60 gallons per day per person in 1915 to 166 gallons per day per person in 1973. The maximum reported groundwater withdrawal for the area was 103 million gallons per day in 1979. Records from most municipalities include long periods for which no ground-water withdrawal data are available. The average annual per capita data among the municipalities varies over the period of record because of incomplete reporting of pumping rates, unusually high pumping rates, short-term economic changes, and other changes not associated with local population changes.
