Whose Water?

California made headlines this month by curtailing water rights for some senior rights holders. But the issue of long-standing water rights is of course not limited to one state, and this recent article looks at the long and fascinating history of water rights on the over-allocated Colorado River. David Owen’s “Where the River Runs Dry” explains that the river currently supplies water to about 36 million people. The river and its tributaries flow through seven states, Colorado, Wyoming, Utah, New Mexico, Nevada, Arizona, and California, and on into Mexico. Every bit of the water has a claim on it, and in fact since the flow has lessened, there are more claims than there is water. [text_ad] The way water is allocated is largely governed by the Colorado River Compact of 1922, which divided rights to the water between the upper and lower basins of the river’s watershed. Unfortunately, it’s now recognized that the 1922 estimate of the river’s annual flow, 17.5 million acre-feet per year, was incorrect; in most years the flow is far less than that. For a while, it didn’t matter because not all the states with rights to the water were using their entire share. Many who live and work in the states that receive water from the Colorado will be familiar with some of the history and negotiations over the river’s flow, but the article includes some interesting concepts. One is that waste and inefficiency in irrigation and water delivery systems are not necessarily a bad thing; they provide a bit of a cushion against drought. For example, when a farmer irrigates a field, most of the excess water—that which isn’t used by the crops or lost to evapotranspiration—runs off and eventually makes its way back to the river or into the groundwater supply. (The argument leaves aside, for the moment, the question of the nutrients or pesticides that runoff might be carrying with it.) If irrigation becomes more efficient, however, then the additional water that’s available tends to be allocated to other uses, leaving less surplus. “Waste, paradoxically, is a kind of reservoir,” Owen notes. “If the residents of a suburb routinely water their lawns, they can stop during a drought. But once they’ve replaced their Bermuda grass with cacti and gravel, and once the water that formerly ran through their sprinklers has been redirected to bathrooms and kitchens in brand-new subdivisions, the enlarged system is more vulnerable in dry periods, because it contains less slack.” The article also includes some interesting facts on Las Vegas’s water use—and they’re not what you might think. The rapidly growing city has some of the country’s toughest water conservation regulations and uses less water today than it did 15 years ago.