Higgins Lake, a popular recreation area in the north-central Lower Peninsula of Michigan, drains an area of 58 square miles and is composed of two deep basins separated by a narrow channel between Flag Point and Point Detroit.The North and South Basins have a maximum depth of about 141 and 100 feet respectively. Ground-water inflow is the major source of the lake’s water supply, with precipitation and inflow from two small tributaries providing the remaining water. The quality of the lake water near shore has been affected by residential development. The concentration of chloride and turbidity in the lake water near the shore increases with increases in building and road density. Nitrogen concentration in lake water near shore also has increased the most in areas where buildings exceed a density of 0.50 building per acre. Ground water beneath the lake showed higher concentrations of phosphorus, nitrogen, chloride, and boron than the lake-water samples. Escherichia Coliform (E. coli) bacteria was found in ground water at sites where building density exceeded 0.40 building per acre, indicating that water from septic systems, is leaching to the ground water that flows to the lake. Phosphorus concentration in lake and ground water appears to be more affected by site-specific conditions, such as soil type and distance of sampling sites from individual septic systems, than by building density alone.