In this March 31, 2017 photo, a thick layer of mud coats the earth around an irrigation canal where high flow in rainy season creates a 30-foot-high spray, near the Endho reservoir, Hidalgo state, Mexico. In brochures promoting the new wastewater treatment plant, the National Water Commission called the use of untreated sewage for farming &#8220;a public health problem&#8221; and a source of environmental pollution. (AP Photo/Rebecca Blackwell)