News Flash (Not): Western Water in Peril

Yes, it rained and snowed a lot this winter and left us with an epic Sierra snowpack. Now forget all that. The long-range outlook: still dry.

A new report from the federal Bureau of Reclamation may offer the most comprehensive forecast yet for western water in the 21st century — but few surprises.

The report, Managing Water in the West, breaks down the outlook for eight key river systems, including three vital to California. The overall message is predictably sobering.

The risks that California faces from climate change are pretty well known, says Peter Gleick of the Oakland-based Pacific Institute. He says the 200-plus-page report “doesn’t offer any new surprises about those risks — but it does reaffirm those risks in an increasingly compelling way.”

Lake Oroville reservoir during California's recent three-year drought. (Photo: Craig Miller)

Some media coverage of the report seems to conclude that California gets off lightly in the study. But the section of the report covering the critical Sacramento and San Joaquin basins seems sobering at best. While it does predict a small (0.6%) increase in annual precipitation on the Sacramento, the report also foresees a drop in San Joaquin precipitation of somewhere between 4.2% and 5.3% by 2050.

Any decrease in precipitation would be significant, especially for a river system like the San Joaquin, which Gleick calls “grossly oversubscribed.” He says that given the other stresses on water supply, such as rising temperatures, evaporation and demand, “Precipitation has to go up, just to break even.”

The report projects a 5-6-degree rise in temperatures during this century, in California’s Central Valley. And whether total precipitation rises or falls, how and when it comes down is just as critical to water supplies. The DOI report predicts that as more arrives as rain, rather than snow, we’ll see more runoff occurring in the winter and less in summer, when it’s most needed. And the infrastructure of dams, reservoirs and aqueducts in place in California were designed for “yesterday’s climate, not tomorrow’s climate,” according to Gleick, who has studied the state’s mountain hydrology for decades.

“It’s a very comprehensive report. It really integrates the state of the science,” says Gleick. “They’re telling us we really need to pay attention to these problems.”

  • Doris Grinn

    If we are having record high precipitation,
    but our surface water reserviors can’t hold it all,
    and our summer temperatures are increasing
    (which increases the ‘evaporation loss’ in this big reserviors),
    then why not USE THIS HIGH PRECIPITATION
    TO RE-FILL OUR UNDER GROUND WATER RESERVIORS.

    Re-filling or re-charging our ground water reserviors will eliminate
    the ‘evaporation loss’ from open, surface water reserviors.
    And since many groundwater reserviors are depleted,
    there is plenty of room to store water in them.

    And we DON’T HAVE TO BUILD new ground water reserviors.
    We just have to ALLOW ground water recharge…and
    we just need to clean up contaminant sources to ground water.

    We need to recognize that all our concrete, ashalt, & buildings,
    along with erodable, bare ground with no ground vegetation,
    will PREVENT the natural absorbtion and re-charge
    of precipitation into our ground water tables.

    And, if we can’t allow natural re-charge of ground water tables,
    we COULD technologically re-fill them at access areas
    with piped in water, from overflowing surface reserviors.

    Recharging our groundwater reserviors just might help the intrusion of salt water in these fresh-water ground water tables
    that are being depleted from over pumping of ground water.

    And then again, we could put a population limit on Calif. that matches the availability of our water resources.
    Which is probably a more radical idea
    than re-charging our ground water reserviors.