California’s water year ends; is a fifth year of drought ahead?
September 29, 2015
• 2015 was California’s warmest ever
• And what of El Nino?
As California’s new water year begins Thursday, water managers are looking back on a fourth year of drought and record warm temperatures.
But a growing El Niño in the Eastern Pacific has many Californians hoping that an end to the state’s drought could be at hand.
Water year 2015 continued the trend of surface water shortages for many urban and agricultural agencies. Most notably, the U.S. Bureau of Reclamation’s Central Valley Project had record low deliveries of zero project water to its north-of-Delta and south-of-Delta agricultural contractors and to agricultural contractors in its Friant Division.
The State Water Project provided only 20 percent of its urban and agricultural contractors’ requested amounts.
Statewide, the only bright picture was the Colorado River service area, where contractors for this interstate supply continued to receive their full allotments.
Efforts at water conservation by urban users have seen water use cut by about 30 percent compared to the same months in 2013, according to the State Water Resources Control Board.
The statewide snowpack on April 1 held only 5 percent of the average water content on that date, in records dating to 1950. The previous low record of 25 percent of average was set in 1977 during one of California’s most significant droughts and was tied in 2014. Of the nine April 1 snowpack values below 50 percent of average since 1950, three have occurred in the past three years of drought.
According to the California Climate Tracker, the winter average minimum temperature for the Sierra Nevada region was 32.1 degrees Fahrenheit, the first time this value was above water’s freezing point in 120 years of record-keeping. The few winter storms of the past two years were warmer than average and tended to produce rain, not snow.
With virtually no snow in the mountains to melt, storage in the state’s reservoirs has been much lower than average. The Department of Water Resources continuously tracks storage in 154 reservoirs around the state, and as Water Year 2015 ends, they hold only 54 percent of their historic average, the agency says. Storage in Northern California’s major reservoirs (as percentages of their historic averages for this time of year) also is far below normal: Lake Shasta (59 percent), Lake Oroville (48 percent), Trinity Lake (33 percent), Folsom Lake (32 percent) and New Melones (20 percent).
Water Year 2016 – the El Niño Question
The periodic warming of surface waters in the equatorial Eastern Pacific Ocean, known as El Niño, was first observed in the 1800s and has been studied intensely for its observable effect on weather patterns around the world – including, on occasion, heavy precipitation in California.
El Niños are categorized as weak, moderate or strong depending on how much the surface temperatures increase and on certain atmospheric measurements.
According to the National Oceanic and Atmospheric Administration’s Climate Prediction Center, there is about a 95 percent chance of a strong El Niño during the coming winter, meaning the water temperature will be 2.7 degrees Fahrenheit or more warmer than normal.
Six strong El Niño events since 1950 produced wet conditions in Southern California, but only the strongest ones in water years 1983 and 1998 brought significant precipitation throughout the state.
In the four other strong El Niño years, the critical up-state water-collecting regions received far less rainfall. It is still too soon to know whether the building El Niño will be a drought-buster or simply a bust, says DWR.
A fifth year of drought certainly is a possibility, the department says. California has experienced two six-year droughts in the past nine decades – 1929-34 and 1987-92.