By Jay Lund
Summary of conditions
February 2016 has been dry, despite El Nino-besotted promises of aqueous abundance. There is sometimes a difference between climatic conditions and hydrologic reality (and economic reality).
Annual precipitation and snowpack are now about average or a little less. Fortunately, the largest reservoirs continue to fill slowly, relative to previous drought years, with still about 6 million acre ft of surface water storage deficit for this time of year. Groundwater will be recharging, as it should this time of year in most places, but we still sit atop a large dry hole.
California remains in a drought, with little doubt. So far, El Nino has brought us largely average precipitation and snowpack. Overall 2016 drought conditions are likely to remain unclear until March, but 2016 will be less dry than 2014 or 2015, but not a drought-buster.
Here are some recent highlights, with links from the California Department of Water Resources’ California Data Exchange Center (CDEC) at http://cdec.water.ca.gov.
Reservoir and Groundwater Storage Conditions
Major reservoirs in California continue to fill much more than last year, but overall remain substantially less than the historical average for this time of year. Some reservoirs, such as Folsom, have filled their water supply levels and are encroached into their normally-reserved flood storage capacity. But California’s reservoir storage remains about 6 maf (about 6 full Folsom reservoirs) less than average for this time of year. Groundwater statewide will be making some recovery but will be a long way from recovering from drought in many places.
The drought by 2015 depleted total storage in California by about 22 maf cumulatively or nearly a year’s worth of water use in agriculture. Soil moisture conditions were also unusually dry following 2015, diverting and delaying some runoff from early storms. Storage is recovering during this wet season, but still has a good bit to go, probably 17-20 maf of drought storage drawdown remains.
- http://cdec.water.ca.gov/cgi-progs/products/rescond.pdf
- http://cdec.water.ca.gov/cgi-progs/reservoirs/RES
Precipitation and Snowpack
Northern Sierra 8 Station Precipitation Index (inches) (tiny totals, compared to average, in yellow)
At the end of January, precipitation and snowpack were above average for that time of year. At the end of February, both precipitation and snowpack are a bit below average. Enough to have a ski season and to be filling some reservoir space – but not what we had hoped for. Precipitation in Northern California is almost what it was for all of last year, with another month or so of wet season left. Precipitation in the San Joaquin and Tulare basins already greatly exceeds last year’s miserable totals.
El Nino apparently is giving us about average conditions. Far better than the last four years. But no drought-buster. It will be hard for the drought to be over for much of California in 2016, but it should be better than 2015 and 2014.
Snowpack:
- http://cdec.water.ca.gov/cdecapp/snowapp/sweq.action
- http://cdec.water.ca.gov/cgi-progs/snow/PLOT_SWC
- http://cdec.water.ca.gov/cgi-progs/products/swccond.pdf
Precipitation:
- http://cdec.water.ca.gov/cgi-progs/products/PLOT_ESI.pdf – Sacramento Valley
- http://cdec.water.ca.gov/cgi-progs/products/PLOT_FSI.pdf – San Joaquin Valley
- http://cdec.water.ca.gov/cgi-progs/products/PLOT_TSI.pdf – Tulare Basin
Concluding thought
Much better than the last four years, but still a drought. A dry February has set back an already likely-to-be-long drought recovery. We are looking at another drought year, with lingering drought effects even if the next two months are quite wet.
Where did El Nino go? Climatologically he is still there, but the hoped-for hydrologic abundance has not yet happened. Fortunately, the forecast is hopeful for early March.
UC Davis’ ongoing seminar series on drought impacts and policy continues. All are welcome. Details at: https://watershed.ucdavis.edu/education/classes/california-water-policy-seminar-series-drought
Jay Lund is Director of the UC Davis Center for Watershed Sciences and Professor of Civil and Environmental Engineering at UC Davis.
Further Reading
Swain, D., “Recent record warmth to be interrupted by Wednesday storm; long term prospects mixed” California Weather Blog, February 16, 2016
Paul Ullrich (Video): Drought in California: A climatological look at water in a semi-arid landscape. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, January 13, 2016
Jay Lund (Video): Drought and Water Management in California. UC Davis School of Law and Center for Watershed Sciences Water Policy Seminar Series, January 6, 2016
How many years does it take for a lowered yearly rainfall/Sierra snow depth become the new norm? e.g., when do repeated low rainfall years, which we term drought, become understood as the expected rainfall? If it ain’t a’gonna happen, let’s stop cheerleading for rain to save us like John Wayne and the cavalry!
DWR (codec) snow report needs improvements to help people understand how much snow water is stored in acre feet for each river storage basin just like the reservoir report.
Interesting observation. Water stored in snowpack is less than water than becomes available as streamflow in rivers or infiltration to groundwater. Some of this water is lost to the atmosphere by sublimation from the snowpack, evaporation of meltwater, and evapotranspiration of meltwater by plants. This will vary with location and weather. But I expect that estimates are made of these.
Historically does ENSO, while “occurring”, bring less snow pack to the southern Sierra? I would think that the southern Sierra would be closer to a more average snowpack than it currently is knowing that ENSO is more effective in the southern regions vs. the middle and northern Sierra?
Each El Nino seems to be more different than popularly thought.