More than two-thirds of the planet is covered by water. Because water is vital to all life, both the quality and availability of this precious nature resource is critical. Investigate point and nonpoint sources of pollution, consider the potential environmental, economic and health effects of water pollution, and see what scientists look for when they test the water quality of North America's largest estuary -- the Chesapeake Bay! When the supply of available fresh water is overused, polluted or affected by climate change, a whole new problem arises -- water scarcity. Learn what can happen when an area's water supply dwindles, and see how conservation and innovation can help to combat this problem. From the passing of the Clean Water Act in 1972 to the building of desalination plants, discover some of the tremendous strides that have been made in maintaining the quality and quantity of the world's water supply.