As climate changes, more water storage will be needed – meaning dams

The first thing to remember about precipitation in California is that it’s unpredictable, as the past several winters have proved again. Several years of severe drought ended in the 2016-17 winter with near-record rain and snow, filling the state’s badly depleted reservoirs.

The 2017-18 “water year,” as hydrologists call it, began with what seemed to be a return to drought but then, in March, we got a steady stream of storms that added to the Sierra snowpack upon which Californians are so dependent.

It might not have been a “March Miracle” on the scale of 1991, when the mountains were virtually bare of snow until one month of heavy storms arrived. But what happened last month was at least a minor miracle, increasing the snowpack to more than 50 percent of average.

Combined with water left from 2017, California will enter the hot months with fairly healthy water reserves.

Not only have the past several years demonstrated anew that “normal” is alternating periods of wet and dry, they also underscore just how dependent California is on its massive array of reservoirs, canals and other waterworks.

It collects water during the wet periods, as it did in 2016-17, and releases its reserves to maintain human life, wildlife and economy when conditions turn dry. Life as 39 million Californians know it would be impossible if not for the state’s water system built by federal, state and local governments.

Hydrologists believe climate change will have a massive effect on our water supply in coming decades, perhaps making the peaks and valleys of precipitation steeper and deeper and with far less snow and far more rain.

If that’s true, our largest and most important reservoir – all that Sierra snow – will be diminished. That means we need to replace the snowpack with more man-made storage, allowing us to capture more rain.

The need for more storage has been evident for decades, and though Southern California’s water agencies, particularly the Metropolitan Water District, have been diligent about adding it, Northern California, where most of the rain falls, has been negligent.

The last state water bond issue contained several billion dollars to jumpstart planning for new storage projects, particularly Sites reservoir – an off-stream site on the west side of the upper Sacramento Valley – and Temperance Flat on the San Joaquin River near Fresno. Combined, they would about 3 million acre-feet of storage, or about what Lake Oroville contains.

But the California Water Commission has been lackadaisical about moving these projects along for reasons known only to themselves.

Meanwhile, there’s some movement on a long-standing proposal to raise Shasta Dam and expand Lake Shasta’s storage, now 4.5 million acre-feet – a project that is much more controversial because of its effects on land local Indian tribes consider to be sacred.

If we continue to drag our feet on building more storage, we will pay the price. And it will be steep.

This story was originally published April 10, 2018 at 10:07 AM with the headline "As climate changes, more water storage will be needed – meaning dams."