The Southwest Offers Blueprints for the Future of Wastewater Reuse Lake Powell, a man-made reservoir on the Colorado River in Utah and Arizona, is the nation’s second-largest reservoir by maximum water capacity, supplying water to several Western states. This story is part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story. No country is immune from water scarcity issues — not even the world’s wealthiest country, the United States. The southwestern states, in particular, have faced frequent and ongoing droughts over the past two decades, and traditional water supplies are failing. As groundwater supplies in the region have depleted substantially, rainfall has decreased and the costs of importing water have risen substantially.