Two million years ago, as glaciers carved much of North America, torrential rains flooded what is now the Western United States, forming vast lakes across the region. The only remnants of that era are millions of saline ponds, some so small that over a hundred can be concentrated into a square kilometer. These lakes are now quickly shrinking. With less runoff from snowpack, and more water being diverted for agriculture, the lakes’ levels are rapidly decreasing, becoming even higher in salt content.