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Despite some localized problems from two dry years, California's water supply remains in good shape at the start of a new "water year" cycle, according to officials at the California Department of Water Resources.
Reservoir storage totals 87 percent of average, or about 3 million acre-feet below what is usually "carried over" to the next year. (An acre-foot is the volume of water necessary to cover one acre to a depth of one foot and is equal to 325,851 gallons, or enough for one to two households in most areas of the state.)
What kind of winter do California's water experts expect and what will that mean for our water supply and the prospect of a third dry year in a row?
Department experts have analyzed data and have estimated what is possible for the coming water year, which starts on October 1 and runs through next September 30.
The weather outlook for the entire winter is at this time based on relatively sketchy information: El Nino conditions are currently weak to moderate. There is, however, an increased chance of above-average precipitation in Southern California.
However, says DWR lead water supply forecaster Pierre Stephens, starting October 1, "Anything could happen, because next year's runoff depends mainly on future weather."
Water year 2003 will begin with dry conditions in river basins, says Stephens. River levels are particularly low in coastal regions and the southern Sierra, where August runoff was among the lowest in the last 25 years.
Once we get into the wet months of November through March, Stephens says, DWR will be refining its forecasts of river runoff and potential reservoir volumes based on actual precipitation. The first official water supply forecasts will be posted on the DWR website (www.dwr.water.ca.gov) in early December and the first forecasts of snowmelt runoff will be issued in early February.
In Northern California, whatever kind of winter we get, the amount of runoff into the Sacramento River basin, the state's largest watershed, will be decreased due to the residual effect of past drier years on groundwater levels. This year, dry soil absorbed an additional 5 to 10 percent of the runoff that was expected.
For those areas of Southern California that depend on imported water from the Colorado River, continued drought conditions in the Rockies and the Colorado River basin would have a negative effect onstorage in Lakes Mead and Powell.
State Water Project
The Department of Water Resources operates and maintains the State Water Project, which supplies water for agricultural and municipal customers. Below-average carryover storage in Lake Oroville, the key reservoir of the Project, might produce low initial forecasts of water allocation for next year. A dry winter would further affect the project's ability to supply supplemental water supplies to some two-thirds of the state's population and nearly one million acres of farmland.
To focus the awareness of water suppliers and the public on preparing for the possibility of a dry 2003, DWR is organizing a variety of events and exhibits.
DWR is co-sponsoring drought preparedness workshops with the Orange County Water District in Fountain Valley October 24 and with the California Rural Water Association in Perris October 29.
Because rural homeowners with private residential wells often experience problems during droughts, DWR has developed a series of traveling exhibits providing information for private well owners. These exhibits are being displayed in libraries in affected communities.
Two Previous Dry Years
Water year 2001 was California's first dry year following six years of wet to average conditions. Although above-average storage in most of the state's major reservoirs reduced dry-year impacts on many water users, state and federal customers received reduced supplies due to low storage and restrictions in the Delta, the state's main "switching yard" for water.
Water year 2002 was wetter but still in the dry category. Precipitation (rain and snow) has been below average statewide every month since January. Runoff since last October has been about three-fourths of average. In Northern California (north of the Tehachapi Mountains), near or below average snow and rainfall predominated last winter. But a dry spring forced state and federal water projects that depend on northern rivers to again cut back deliveries to agricultural and urban water suppliers. Southern California conditions were extremely dry.
This summer, our state's months of most water use, most of the concerns over water supply centered on Southern California, where many communities experienced the driest year of record. Despite this, customers of most urban Southern California water agencies did not experience shortages, according to Jeanine Jones, DWR drought preparedness manager. Water is imported to many Southern California communities from the Colorado River and Northern California.
Water suppliers most affected by dry conditions in Southern California this year were isolated small water systems in rural areas relying solely on wells. The community of Wrightwood in the San Bernardino Mountains, for example, had to declare a water shortage emergency this summer.