Yale Environment 360: During four of the last 10 summers, more than half of the 800-mile Tarim River in northwestern China ran dry. Landscape ecologist Niels Thevs has been there conducting fieldwork and has watched water shortages take the heaviest toll on downstream cotton farmers, who irrigate six or seven times during the growing cycle. “One could really feel the struggle for water,” Thevs recalls. “People did everything they could.” But their typical strategy — drilling wells — only further depleted the basin’s…