DWR Announces: New Water Year on Tap.

SACRAMENTO, Calif. -- The calendar year begins in January, and the fiscal year begins in July, but hydrologists have determined nature needs her own schedule. Each new water year begins October 1 to coincide with the start of the rainy season and runs through September 30.

That news might not be of much interest to most people, but to water-watchers at the California Department of Water Resources (DWR), it means a lot.

From October 1 to September 30 each year, hydrologists, meteorologists and engineers keep tabs on precipitation (the combination of rain and snow) and runoff in the Northern Sierra and other key watersheds.

The northern Sierra and southern Cascades are of particular importance because that's where most of the state's water supply accumulates. Measurements are taken by gages in the major rivers, including the Sacramento, Feather, Yuba and American.

Meanwhile, snow surveyors will soon don their gear for winter treks throughout the Sierra range to measure snow depth and water content.

All this information enables forecasts to be made of water supply for next spring and summer, the heaviest months of water use by farms and homes.

The past 2005-2006 water year was a wet one, as many Californians remember.

The northern Sierra precipitation totaled 80.10 inches, or 160% of the historic average. For reservoirs in the northern part of the state, generally above Sacramento, that meant a good supply of water to carry to the next season. Shasta Lake, for example, is storing 113% of average, while Lake Oroville tops 124%. By fall, these reservoirs will have room for a possible flood, meeting their flood control requirements. Because of this very wet water year, DWR was for the first time able to deliver State Water Project Contractors 100% of their maximum water entitlements.

Though precipitation for the state is 140% of average to date, September was drier than normal. In addition, temperatures were very hot in July in California and the American Southwest, though mild the rest of the summer. The National Weather Service (NWS) long range forecasts indicate a normal winter in Northern California, but show a good chance for above normal precipitation this winter in Southern California, as well as Arizona, New Mexico and Texas.

Details, Facts and Figures

-- As of August 2006, storage in more than 150 reservoirs on which DWR keeps tabs was at 29.2 million acre feet (MAF), which is about 78% capacity and 123% of average for that date. Last year, storage was at 28.5 MAF at the end of August. An acre-foot is 325,851 gallons, or enough water to cover one acre to a depth of one foot.

-- Storage for the four largest reservoirs on the Lower Colorado River was about 53% of capacity as of August 2006, as opposed to about 56% last year. California's allocation from the Colorado River for 2007 is expected to be its basic entitlement of 4.4 million acre-feet.

-- Precipitation in the Sacramento River Basin, the source of much of California's water supply, was about 150% of average during Water Year 2006. In the San Joaquin Basin, precipitation was about 145% of average, while statewide precipitation was about 140% of average.

-- California mountain snowpack was excellent this year with the April 1 pack at 125% of average, and runoff further boosted by a wet April.

-- California experienced two significant flood events during water year 2006. The New Year's Eve flooding that extended into January 2006 caused extensive damage in Sonoma and Napa counties. The early April floods on the San Joaquin River required a major sandbagging effort to shore up weakened banks.

-- Governor Arnold Schwarzenegger declared a state of emergency for California's Central Valley levee system, and placed 29 critical erosion sites on a list for immediate repair. Subsequently, four sites were added to bring the total to 33 critical erosion sites.

The Department of Water Resources operates and maintains the State Water Project, provides dam safety and flood control and inspection services, assists local water districts in water management and water conservation planning, and plans for future statewide water needs.