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The California Drought of 2015: A preview





March 30, 2015 - This fourth year of drought is severe, but not yet the driest ever.


Jay Lund


California WaterBlog


This fourth year of drought is severe, but not yet the driest ever. The drought’s impacts are worsened by record heat, which has dried out soils and raised the demands for irrigation, and the historical high levels of California’s population, economy, and agricultural production, and historical low levels of native fish species. There is need for concern, preparation and prudence, but little cause for panic, despite some locally urgent conditions.

How dry?

This year will be about as dry as last year. This is bad, as 2014 was the fourth to eighth driest year in 106 years of recordkeeping, by most reasonable reckonings. This year will be a little different overall, but quite different in some areas, both better – Santa Cruz – and worse – eastern San Joaquin Valley.

Statistically, last year’s drought is about a one in 15-30 year event. With a changing climate and growing water demands, we should prepare for such droughts occurring more than once a generation.

As detailed below, Northern California will be critically dry, having about the same precipitation as 2014 (more in some basins), less snowpack and more storage in some of the largest reservoirs.

The southern Central Valley is as dry or drier than 2014, with abysmal precipitation and snowpack. The western side benefits from having more water stored in San Luis Reservoir than in 2014, but the eastern side has less water remaining in its major reservoirs. Southern California is in similar shape as in 2014 for surface water. Little time is left in California’s “wet” season, and the forecast for the coming week or so is quite dry. What we see is probably what we’ve got.

Water allocations for the State Water Project are small (20 percent), but better than last year’s 5 percent allocation. Federal Central Valley Project allocations are likely to be 75 percent (and perhaps 100 percent) for higher-priority contractors, 25 percent for cities, and zero for everyone else.

Some locally supplied eastern San Joaquin Valley irrigation districts are delivering no more than 30-35 percent of normal supplies; Merced Irrigation District is delivering no surface water.

Junior water-right diversions in the Central Valley will be curtailed. After reservoir withdrawals last year and little refill this year, eastern San Joaquin Valley will be hit much harder this year. Tulare basin water shortages are about like 2014 or worse, and Sacramento Valley shortages are about the same or a bit less.

Almost the entire state has less groundwater because of three previous years of drawdown. More wells are likely to go dry, particularly for rural households and small water systems, but probably also some irrigation wells.

What will we do?

California will not run out of water this year, or next, if we are careful. We will respond mostly as we did last year, with some modest changes.

In rough order of importance, California will make up most of this year’s water shortage by:

Additional groundwater withdrawals of perhaps 5 million or more acre-feet
Reductions in urban and environmental water uses and agricultural fallowing — totaling perhaps 4 million acre-feet
Shifting perhaps 1 millon acre-feet of water use from lower to higher economic values through water markets
Depleting reservoir storage by perhaps 1-2 million acre-feet
Increasing wastewater reuse and other conservation efforts

Making rain is not an option.

In many places, groundwater will be less available and farther from the surface than last year, with more dry wells and more expensive pumping. Somewhat more surface water will be available in some places, including the North Coast, Santa Cruz, Sacramento Valley and western San Joaquin Valley. Less will be available for eastern San Joaquin Valley. Further reductions in urban water use are likely for the Bay Area and Southern California.

Drought impacts on fish and wildlife and hydropower should be similar to those in 2014.

California is not running out of water

Economic and environmental factors will dampen many popularly espoused or feared actions, such as widespread ocean desalination, extensive capturing of stormwater, vast reuse of treated wastewater, eliminating exports of water-intensive foods, abandoning major irrigation districts, fog water collection, iceberg towing and importing water from Canada, the Colombia River, the Great Lakes or anywhere else.

Less extreme water management activities should be adequate, less costly and better environmentally, even for much more extreme droughts than today’s. California is not running out of water.


Droughts bring public and political attention needed to make major changes in water management, such as last year’s historic groundwater legislation. Strategic changes usually require serious long-term problems and thinking, and the urgency of a drought or flood to focus policy discussions.

What changes are likely from this year’s drought? It is hard to know now, but here are some promising candidates:

Water measurement and accounting. The 2009 drought brought legislation that began improving basic data on surface water use and groundwater levels. Much more is needed to tighten California’s water accounting closer to that of other western states. Improved water-use data is unlikely to require massive new reporting, but rather improved coordination of existing reporting, some new reporting, and perhaps remote sensing estimates of crop water use (as is done in Idaho). Some additional reporting, such as requiring large water users to “call” their use during drought, would improve use of available water and add reliability to both senior and junior water rights. For better accounting to occur, the state needs a common comprehensive and workable regional water accounting system serving both the State Water Resources Control Board and the Department of Water Resources.
Groundwater. A dry 2015 seems only likely to accelerate implementation of local and state groundwater sustainability efforts. Perhaps the best outcome would be legislation to speed groundwater basin adjudications and better empower and guide local groundwater sustainability agencies. Consolidating state groundwater data and analysis now scattered across agencies and programs would be another positive outcome.
Water markets. More expeditious and transparent trading of water rights and longer-term water rights contract. From a statewide perspective, the amount of water traded would be small, but the economic and environmental benefits would be great. Water markets are also probably the best means to provide flexibility and incentives needed to improve groundwater recharge, coordinate storage operations, appropriately conserve water, and revitalize environmental water management.
Reducing net water use. A primary response to water shortage is to reduce water use in ways that conserve the most water with the least economic and environmental cost. This applies to all water-use sectors during droughts and in the longer term. Improving water rate structures and economic incentives with pricing and markets will be important here, even for some environmental water uses.
Sacramento-San Joaquin Delta. Water diversions from the Delta are unfortunately central to California’s water system. They will be less during a drought, but what remains becomes quite valuable. The economic value of the diversions will likely increase with climate change and groundwater sustainability, as local areas seek additional external water supplies. After groundwater, the Delta is probably the state’s most strategic water problem. This year’s drought will provide opportunities and motivations for long-term progress on managing the Delta.
Overall, the drought of 2015 will be a challenge. We can complain and suffer with the usual lament over water waste (by others, of course), or we can make inconvenient and sometimes costly changes for the better.

Jay Lund is a professor of civil and environmental engineering and director of the Center for Watershed Sciences at UC Davis.

Some arid details at the end of March

Precipitation and snowpack

No “Miracle March” this year. We had appreciable precipitation only in December and February — one sizable storm each month. The other months were almost entirely dry for most of California.

North Coast streams are in better shape, but the Sacramento Valley is only slightly wetter than in 2014. San Joaquin and Tulare basins are about as dry as this time last year, with dry weather forecast for the short remainder of the “wet” season. 2015 could be the driest year of record for the southern Central Valley.

Snowpack is a little worse than last year, perhaps the driest on record statewide.

As of March 29, the Northern Sierra (Sacramento Valley) Precipitation Index was down to 76 percent of average to date, slightly higher than that for all of 2014. Source: California Data Exchange Center.

Precipitation is less than half of average for this time of year in the San Joaquin Valley. Snowpack is a little worse than last year, perhaps the driest on record statewide. Source: California Data Exchange Center.

Tulare basin has a shorter record though it has the most water use in California. Source: California Data Exchange Center.

Snowpack is truly sad, about 6 percent of average for this time of year. Source: California Data Exchange Center.


Reservoir storage is better overall than last year. Still, it’s about 6 million acre-feet below average with no prospect for much refill from snowmelt. The big reservoirs in the Sacramento Valley are 1.3 million acre-feet fuller.

Storage south of the Delta is about the same, though distributed differently. San Luis Reservoir, which serves the state and federal water projects, is about 600,000 acre-feet higher than they were a year ago, but the large reservoirs on the San Joaquin River tributaries are about 600,000 acre-feet lower. Exchequer Reservoir is at 9 percent of capacity.

Source: California Data Exchange Center.


Groundwater storage is probably about 6 million acre-feet less than this time last year. Aquifer levels will generally be lower than a year ago in the areas highly dependent on groundwater.




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