I try to keep up with the latest news, but by no means could I use this blog to break news. That said, developments in the past couple of days are must-reads for anyone interested in water resources. The water in the southwest is just not there this year, folks, and it’s starting to dawn on people how precarious our water supplies can be. The simple case is San Luis Reservoir, which supplies much of the South Bay – wealthy homes in Los Altos, Saratoga, and Cupertino, as well as industries in Silicon Valley. The reservoir is at historic lows — 17% of full pool — because of one of the driest rainy seasons on record, combined with cutbacks in flows out of the Sacramento-San Joaquin Delta have cut off much of the typical inflows, while outflows, in the form of residential, industrial, and agricultural demand, continue unabated. This year isn’t the year that water will have to be rationed within the San Jose area, according to officials, due to extra storage on-hand in groundwater and smaller reservoirs, but the Santa Clara Valley Water District should be pushing for conservation among its customers and a resolution to the long-term plans for the Bay-Delta, such as the tunnels, perhaps, to shore up their water reliability…
The reliability of the Colorado River’s flow has been debated since the first compact over-allocated the water rights based on wetter than average years. We’re in a 14-year drought on the Colorado, and now 40 million people’s drinking water and some 15% of the nation’s produce depend on it. Remarkable numbers, but that’s what happens when there’s only one “major” water source in a 7-state region, and it’s not even one of the top 25 rivers in the US in terms of discharge (at 1400 cubic ft per second on average, the Colorado is #28 of America’s 38 rivers over 500 miles long). Lakes Powell and Mead, the largest two reservoirs in the US, help bridge the gap between high and low flows on the Colorado, but both are struggling to keep pace with the drawdown of the past 14 years. Again, inflows are limited, and outflows just keep coming.
The Bureau of Reclamation, which operates both reservoirs, announced on Friday that less than 10% of the normal allocation would be available from Lake Powell this water year (starting October 1st), the lowest amount since the reservoirs were first filling in the 1960s. This sets the stage for a legal “shortage” (also known as a “call”) to be declared in the next couple of years, which kicks in provisions to cut off water to Arizona, California, Nevada, and Mexico. Arizona, last in line for water rights, loses supplies first, followed by Nevada and California. Arizona will rely on its banked groundwater, stored in the “good years” of high runoff. Las Vegas, which pulls supply from Lake Mead and discharges its treated wastewater into a tributary of the lake, will kick into gear a controversial plan to build a $7 billion pipeline to a groundwater resource in rural eastern Nevada, along the border with Utah. And California’s farmers in the Imperial Valley, the largest consumers of Colorado River water, will have to be careful about taking only as much water as they’ve been allocated.
This can’t be a surprise to those who’ve been paying attention, from the Bureau of Reclamation’s farfetched feasibility study released last winter to the paper out of Scripps in 2008 that predicted a 50% chance that Lake Mead would be dry by 2021. Savvy water managers across the southwest have been preparing policies and working out deals for what to do when the inevitable water shortage hits. Thankfully this means resolution in a meeting room rather than in a court room. But let’s hope that the public’s eye doesn’t forget this wake-up call if we have a particularly wet winter and seemingly resolve our troubles with plenty of water to go around. We had a very wet year in 2011, which increased Lake Mead around 40-50 ft, and Lake Powell around 50 ft. The problems did not go away; the “shortage” risk was merely delayed.