In january, it rained a lot in Southern California. The usual street intersections flooded. Water tumbled down the Los Angeles River. And houses in areas ravaged by fires last fall seemed in danger of sliding off their hilltop perches.
It was chaotic, as always -- but desperately needed. The wet weather came after the driest year on record in the L.A. Basin -- less than 3.5 inches of rain. Coupled with below-average rainfall in 2006, lack of rain in 2007 had fed fears of a drought. Do last month's downpours mean we can stop worrying now?
There is no simple, single definition of drought. In any region, there are periods of below-normal precipitation. These dry periods become a drought when demand for water exceeds supply. In this sense, we may be in a permanent drought throughout the Western United States.
Wet and dry extremes are a natural part of California's climate. Since 1900, the state has experienced eight multiyear dry periods. Major droughts occurred in 1929-1934, 1976-77 and 1987-1992. Researchers have identified more extreme dry periods going back centuries.
So far, 2008 has been a wet year. At the end of January, rainfall in downtown Los Angeles totaled just over 12 inches, well above the seasonal average of 8 inches. The Sierra Nevada snowpack, the major source of fresh water for Southern California, is currently 18% above average for this time of year. And meteorologists forecast more rain and snow.
But we need a lot of rain to make up for last year's shortfall. Precipitation throughout California in 2007 was only 65% of normal. It was between 15% and 30% of normal in Southern California. The Sierra snowpack was a meager 25% of normal. While reservoirs in Southern California are relatively full, they supply only a small fraction of the region's water. Reservoirs in the rest of the state, by contrast, are low compared to the average for this time of year. And groundwater basins throughout California remain overtapped. Just as a single dry year does not necessarily constitute a drought, a single wet year may not end one.
But several new factors are making it harder for water managers and planners to say if we're in -- or out -- of a drought. One of the most important is climate change caused by global warming. In its most recent assessment, the Intergovernmental Panel on Climate Change, a scientific body that studies the effect of human activity on the climate, noted that droughts have become more common. It forecast that droughts will become more frequent and intense as atmospheric greenhouse gas concentrations continue to rise. And as temperatures warm, crops, lawns and swimming pools will likely require more water.
Mismanagement of our water supplies can also produce a drought. For instance, overuse of water from the Sacramento-San Joaquin River Delta has caused an ecological crisis there. The amount of water pumped out of the delta rose to record levels after 2000. As a result, the delta smelt, some salmon populations and other fish species are rapidly declining. In response, the courts have ordered the state to dramatically reduce the amount of water it pumps out of the delta, effectively creating a policy-induced drought throughout California.
Fortunately, the recent spell of wet weather has allowed the state Department of Water Resources to increase the deliveries from the delta to farmers and cities in Southern California, the Bay Area and the Central Valley. Still, these amounts are way below the levels farmers and cities desire. And the state's continued population and economic growth, particularly in hotter inland areas, will put additional stress on its limited water resources.
The fact of the matter is that droughts will come and go. Managing our water system from drought to drought, however, does little to reduce our vulnerability to fluctuations in rainfall. California can do a lot more.
First, we must find new sources of water. We could build another dam, tap the next river over the mountain or pump another groundwater aquifer. But these sources have been over-tapped already. There are more innovative ways to increase water supplies.
Every year, billions of gallons of wastewater are dumped into our rivers and oceans. This water can be treated and reused for a variety of purposes. For instance, the Orange County Water District recently completed a recycling facility that produces 72,000 acre-feet a year of high-quality water. Similarly, the Irvine Ranch Water District currently meets nearly 20% of its water demand with recycled water.
Second, we must reduce our demand for water. New front-loading washing machines, for instance, use 40% less water than their older cousins, and new toilets use one-quarter of the water used by older models.
A commitment to developing alternative supplies and using our existing supplies more efficiently -- rather than simply hoping for rain -- will help ensure that we have sufficient resources to maintain a healthy environment, a prosperous agricultural sector and a vibrant economy for future generations.