The silvery blue waters of the Great Salt Lake sprawl across the Utah desert, having covered an area nearly the size of Delaware for much of history. For years, though, the largest natural lake west of the Mississippi River has been shrinking. And a drought gripping the American West could make this year the worst yet. The receding water is already affecting the nesting spot of pelicans that are among the millions of birds dependent on the lake. Sailboats have been hoisted out of the water to keep them from getting stuck in the mud. More dry lakebed getting exposed could send arsenic-laced dust into the air that millions breathe.