Branch County has abundant water resources throughout most of its area. Almost all the water used is supplied by wells that obtain water from glacial drift deposits and locally from fractures and sandy beds in the Coldwater Shale. Glacial drift in buried bedrock valleys may yield large quantities of water to wells. Well yields are generally adequate for domestic and farm supplies. Properly developed large-diameter wells tapping thick beds of sand and gravel of the glacial drift can yield up to several thousands of gallons per minute locally. The hundreds of lakes and the many perennial streams have great recreational value. They are also a large potential source of water for some supplies. For example, it is estimated that 88 billion gallons of water runs off in streams of the county in an average year, and the lakes o the county hold about 42billion gallons of water in storage.
Problems of water supply to wells exist locally in some moraine and till areas of where the glacial drift is thin and the underlying bedrock yields only small quantities of water or none at all.
Ground water is generally hard to very hard and often contains excessive iron. Salty water is mainly a problem in areas where bedrock is the chief source.
Floods are not a serious problem largely because of the storage capacity of the lakes and the permeable materials in some stream basins. Based on measurements at eight stream sites the estimated amount of flow for 90 percent of the time ranges from 80,000 to 150,000 gallons per day per square mile of drainage area.
A special study of low levels in land-locked Gilead Lake indicated that this lake is semiperched and mostly dependent upon the water table for tits levels.
