The Colorado River’s Future

Last month, Ken Salazar, the secretary of the interior, committed $1.5 million to establish a study group focusing on the Colorado River basin. Modest as the dollar amount sounds, this is a very good investment. The study will be the first of three river basin studies — called the WaterSMART program — aimed at measuring the nation’s water demands and resources, including the potential impacts of climate change. Starting with the Colorado River makes sense. Since 1922, its water has been allocated among seven Western states under a legal compact. The amount each state can draw from the river is based on water levels measured in 1922, after several wet years. There is a big gap between the amount of water flowing then — about 16.4 million acre-feet per year — and the actual flow in normal years, which averages about 13.5 million acre-feet. Historical tree-ring samples, whose growth patterns indicate rainfall, suggest that the recent drought is not an anomaly and that drought has been the normal condition in much of the river basin for centuries. And droughts are likely to continue as the climate warms. So far the states have been making do, thanks to water stored in reservoirs along the river. But they are managing a depleted resource with a forbidding future. Lake Mead, near Las Vegas and the largest reservoir on the river, is at its lowest level since it was first filled 75 years ago. The river’s flow is approaching the low-level mark that would allow states in the upper basin to withhold water from states in the lower basin — a change that would hit Nevada hardest...more