The Great Lakes are the world’s largest source of surface fresh water.  Communities can and sometimes do take water directly from the lakes.  This practice is more and more risky as the number of people living on the lake shore increases.  A ground water source is very convenient for many communities because the ground is a superb filter which purifies water.  The Pilgrim River delta has sandy sediments in it which provide excellent water quality, better than can be obtained from pumping directly from the lakes.  The idea is to drill into the delta sands and pump water out so that recharged water will be progressively filtered. The Houghton Water supply comes from the Pilgrim River delta (see the wellhead protection area).  Houghton and Hancock sewerage is purified at the sewer treatment plant before it is reintroduced to the lake.  At the Sands, you can map the locations of the water supply and sewerage treatment facilites.  You can also map the extent of the Pilgrim Delta and Isle Royale Sands.  And you can plot the water supply system in cross sectional view.