Accumulated precipitation for northern California, 35% less than average and one third of 2017!

by Jay Lund

Despite this week’s rain and snow, California is back to dry conditions again after a very wet 2017.  With about four weeks left in the normal wet season, the Sacramento Valley is at about 65% of average precipitation (less than 1/3 of last year’s precipitation).  The southern Central Valley has less than 50% of average precipitation and southern California is still drier.  Snowpack is much less, at 37% statewide.  Surface reservoirs, which almost all refilled and spilled in record-wet 2017, are now at 98% of average for this time of year, and will fall quickly as there is well-below-normal snowpack to melt.  The large water projects are expecting to make some water deliveries, but much less than last year.  Groundwater, California’s largest reservoir, is in mostly good shape in northern California, but in the drier parts of California has not nearly refilled the additional pumping from the last drought.  Even if March is very wet, 2018 almost certainly will be dry.

Does this mean California is back to drought?  Some, but mostly not yet.  Drought comes on fast for some areas and more slowly for others.  California’s forests will likely experience drought this year.  Soil moisture and snowpack are the forests’ only reservoirs, and these deplete fast.  Having lost over 100 million trees from the still-recent previous drought, there will be plenty of dead wood and dry conditions for wildfires this year.  Aquatic ecosystems also can be expected to suffer in a dry year, especially as there has been little recovery of Delta Smelt and salmon from the recent drought.

Most cities and agriculture should be able to weather this year’s dryness with water stored in reservoirs and some additional groundwater use.  Some areas will be worse affected, however.  Southern Central Valley agriculture is slated to receive substantial surface water delivery cut-backs compared with last year.

A series of dry years leads to more widespread and deeper effects of drought.  Shallow rural wells are increasingly affected as dry conditions and the depletion of surface reservoirs leads to more groundwater pumping.  More groundwater pumping will make it harder for some regions to comply with the state’s new Sustainable Groundwater Management Act.  The drawdown of reservoirs also leads to problems maintaining flows and cold temperatures for salmon and Delta outflows.  Damages to ecosystems accumulate with additional dry years.

Areas prepared for drought suffer much less than areas with little or ineffective preparations.  But all areas suffer some.  Implementation of the Sustainable Groundwater Management Act is essential for rural areas to prepare for drought, as most agriculture and Central Valley water supplies will always depend on groundwater storage to get through long droughts.  Preparation is hardest for areas that lack organization and regular funding, such as small rural water systems and ecosystem management.  These are among the greatest challenges.

Now is the time for state and local agencies to prepare for drought, before a drought is declared.  Most cities and irrigation districts are now well-practiced for drought, and should now have better plans.  Waterfowl managers were fairly well-organized for the previous drought and introduced some useful innovations.  However, fish and aquatic ecosystem management was largely unprepared for drought, and urgently need plans and preparations for drought. Many water and environmental managers are likely to need drought plans this year.  Even in the best cases, they will need drought plans and preparations all too soon.

Drought and dry years have always accelerated innovation in California’s water management.  Given our climate, California will always have water problems, and opportunities to improve.  Now is a good time to prepare for drought, and to prepare to make other long-term improvements.

Jay Lund is the Director of the UC Davis Center for Watershed Sciences

Further Reading

The mighty California Data Exchange Center, http://cdec.water.ca.gov.  (Showing that some parts of California government do data fairly well – although we would always like more and better.)