By Jay Lund
Wet. After five years of drought, most of California finally has become wet. The mountains are exceptionally wet and covered with snow. The state’s reservoirs are fuller than their long term average (with a few exceptions). Flood control structures are being employed, some for the first time since 2006.
We can now better understand the balance needed for California’s water system – which must operate for many sometimes-conflicting purposes in a climate with wild swings in water availability. Every year, California must operate for drought, flood, public and ecosystem health, and economic prosperity (or at least financial solvency).
Where is California’s Drought today?
Here are today’s numbers:
- Sacramento Valley precipitation – 201% of normal (for this time of year), 113% of average water year total
- San Joaquin Basin precipitation – 206% of normal, 110% of average water year total
- Tulare Basin precipitation – 205% of normal, 106% of average water year total
- Southern California – Mostly more than 150% of normal
- Statewide snowpack – 171% of normal, 110% of average April 1 accumulation
- Reservoir storage – 110% of normal, statewide
- Lake Cachuma (near Santa Barbara) – 16% of normal (the drought remains here)
2017 will not be a surface water drought for California. Precipitation and snowpack in much of the state already exceeds that for an entire average water year. And we still have two months to go in California’s wet season.
Despite these wet conditions, California has remnants of drought, some of which will persist for decades. Some Central Coast reservoirs remain very low. Groundwater in the southern part of the Central Valley remains more than 10 million acre-ft below pre-drought levels. Most of the groundwater deficit is in dry parts of the San Joaquin and Tulare basins, which could take decades to recover – with long-lasting effects on local wells. The millions of forest trees which died from the drought will need decades to recover, if the warmer climate allows. Native fish species, already suffering before the drought, are in even worse conditions today.
Drought indicator myths
Given the variety of drought impacts and conditions, many “drought indicators” seem Quixotic and distract policy and management discussions.
The US Drought Monitor is a common drought indicator, based mostly on soil moisture – designed mostly to indicate drought for rain-fed agriculture. This index is most useful for stress to forests and un-irriggated pasture and crops, which not California’s biggest drought issue. California relies much more on large reservoirs and aquifers, which allow crops and cities to survive otherwise California’s beautiful and devastating dry summers. The US Drought Monitor, while a convenient general public service, is misleading for California’s most common drought issues. National statistics often have such regional problems.
Still less useful, in my mind, is the idea of a “snow deficit” accumulating over drought years. Snowpack in California physically resets to zero each summer as snow melts – Accumulating snow deficit over years has no physical meaning – and little management meaning. Real drought deficits do accumulate as aquifer overdraft, reservoir drawdown, dry soil, and cumulative impacts to forest and fish populations, which can take years or decades to recover. Less snow last year does not reduce water this year except for reduced storage in reservoirs or aquifers – where water deficits are managed and more properly measured or estimated.
Drought indicators should have physical and management meaning, or are more likely to mislead and confuse. Fortunately, California is more successful with managing droughts than developing drought indicators.
Although the drought is largely over, California remains a dry place. As a big dry place, some parts of California can be in drought while others are in flood (contrasting Santa Barbara and Sacramento today). Local and regional effectiveness and adaptability are vital for water management in California.
The end of drought does not solve California’s most important water problems. Groundwater sustainability (implementing SGMA), Sacramento-San Joaquin Delta sustainability, effective ecosystem management, and fixing rural drinking water systems remain major problems. Solving these issues involves difficult water accounting, integrated management, and finance issues at local and statewide levels.
Progress on these long-term issues is harder and requires more persistence than making progress during the urgency of a drought. But we should reserve “drought” management for unusually dry conditions, or risk losing the public confidence that democratic governments and effective water utility management require.
Leaving the drought, California has a clearer picture of the important work that remains to be accomplished. The next drought (and flood) could be coming soon.
Jay Lund is a professor of civil and environmental engineering and director of the Center for Watershed Sciences at UC Davis.
Some further reading
Lund, J., “After drought, California urgently needs to focus on big picture of water management,” Sacramento Bee, Op-Ed, 29 January 2017.