F. R. Twenter N.G. Grannemann 1982 <p>Three test holes drilled at Windigo in Isle Royale National Park in 1981 indicate that the ophitic basaltic lava flows underlying the area contain little water and cannot be considered a source for public water supply. The holes were 135, 175, and 71 feet deep. One hole yielded about 1 gallon of water perminute; the other two yielded less. Glacial deposits seem to offer the best opportunity for developing a ground-water supply of 5 to 10 gallons per minute.</p> application/pdf 10.3133/ofr82567 en U.S. Geological Survey Ground water for public water supply at Windigo, Isle Royale National Park, Michigan reports