A new tree ring study spanning more than 1,200 years is helping archaeologists pinpoint the exact dates of ancient mega-droughts that may have been key factors in the decline of major pre-Hispanic cultures in Mexico and Central America.

U.S. and Mexican officials reached a deal Monday for Mexico to defer part of its water allotment from the Colorado River until 2014 while farmers in the Mexicali area repair irrigation networks damaged by an earthquake this year.

Water levels in Lake Mead, the Colorado River reservoir, fell sharply again this summer and are nearing an elevation that would set off the first-ever official water shortage on the river. The reservoir, which supplies roughly 30 million users in the West, dropped to 1,087 feet above sea level, or about 40 percent of capacity.

A powerful Easter Sunday earthquake along the Mexico border has had ripple effects in Nevada, spurring international talks about future use of the Colorado River and the water level in Lake Mead.

Set amid the wheat fields and melon patches west of downtown, the 60-acre Yuma Desalting Plant is a technological marvel — capable of cleaning 73 million gallons of brackish farm runoff a day, enough for 110 Olympic-sized swimming pools. Built in 1992 at a cost to the federal government of $250 million, the plant was meant to help the U.S.

Anthropologist Kirk French and civil engineer Christopher Duffy of Penn State report on a conduit designed to deliver pressurized water to Palenque, an urban center in southern Mexico, more than 1,400 years ago. "The ancient Maya are renowned as great builders, but are rarely regarded as great engineers.

Like other villages around Mexico, Acasico will soon be submerged under water, falling victim to dam projects aimed at meeting the water demands of factories, vegetable farms and the country's growing cities. Since 2006, the government has flooded 11 villages to build two reservoirs.

Mexico is suffering from its driest year in 68 years, killing crops and