WaPo:
Unrest has simmered for months over U.S. demands that Mexico pay off a shortfall of more than 100 billion gallons by Oct. 24 to meet its five-year water-delivery quota. Local farmers say the extra payments are emptying reservoirs that store water they need.
The crisis erupted in violence this month when about 2,000 protesters swarmed over La Boquilla dam on the Conchas River and a national guard unit was sent in to stop them. One woman was shot dead in the chaotic confrontation last week, but about 200 protesters, armed with sticks and rocks, were able to repel the security forces and retain control of the century-old hydroelectric facility.
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The treaty requires the United States to send far more water to Mexico than it receives, but those payments flow elsewhere on the 2,000-mile border, far from dry Chihuahua, which provides more than half of Mexico’s share. Every year, Mexico pipes about 114 billion gallons of water north from the Rio Grande and Conchas rivers; the United States sends almost 489 billion gallons south from the Colorado River.