It’s bad but not disastrous, as this excellent overview from UC Davis posted on the California Water Blog, concludes.
This fourth year of drought is severe, but not yet the driest ever. The drought’s impacts are worsened by record heat, which has dried out soils and raised the demands for irrigation. There is need for concern, preparation and prudence, but little cause for panic, despite some locally urgent conditions.
This year will be about as dry as last year. This is bad, as 2014 was the fourth to eighth driest year in 106 years of recordkeeping, by most reasonable reckonings. This year will be a little different overall, but quite different in some areas, both better – Santa Cruz – and worse – eastern San Joaquin Valley.
Statistically, last year’s drought is about a one in 15-30 year event. With a changing climate and growing water demands, we should prepare for such droughts occurring more than once a generation.
As detailed below, Northern California will be critically dry, having about the same precipitation as 2014 (more in some basins), less snowpack and more storage in some of the largest reservoirs.
The southern Central Valley is as dry or drier than 2014, with abysmal precipitation and snowpack. The western side benefits from having more water stored in San Luis Reservoir than in 2014, but the eastern side has less water remaining in its major reservoirs. Southern California is in similar shape as in 2014 for surface water. Little time is left in California’s “wet” season, and the forecast for the coming week or so is quite dry. What we see is probably what we’ve got.
Water allocations for the State Water Project are small (20 percent), but better than last year’s 5 percent allocation. Federal Central Valley Project allocations are likely to be 75 percent (and perhaps 100 percent) for higher-priority contractors, 25 percent for cities, and zero for everyone else.
Some locally supplied eastern San Joaquin Valley irrigation districts are delivering no more than 30-35 percent of normal supplies; Merced Irrigation District is delivering no surface water.
Junior water-right diversions in the Central Valley will be curtailed. After reservoir withdrawals last year and little refill this year, eastern San Joaquin Valley will be hit much harder this year. Tulare basin water shortages are about like 2014 or worse, and Sacramento Valley shortages are about the same or a bit less.
Almost the entire state has less groundwater because of three previous years of drawdown. More wells are likely to go dry, particularly for rural households and small water systems, but probably also some irrigation wells.
What will we do?
California will not run out of water this year, or next, if we are careful. We will respond mostly as we did last year, with some modest changes.
In rough order of importance, California will make up most of this year’s water shortage by:
Additional groundwater withdrawals of perhaps 5 million or more acre-feet
◾Reductions in urban and environmental water uses and agricultural fallowing — totaling perhaps 4 million acre-feet
◾Shifting perhaps 1 million acre-feet of water use from lower to higher economic values through water markets
◾Depleting reservoir storage by perhaps 1-2 million acre-feet
◾Increasing wastewater reuse and other conservation efforts
Retrieved March 30, 2015 from http://californiawaterblog.com/2015/03/30/the-california-drought-of-2015-a-preview/