by John R. Durand, Fabian Bombardelli, William E. Fleenor, Yumiko Henneberry, Jon Herman, Carson Jeffres, Michelle Leinfelder-Miles, Jay R. Lund, Robert Lusardi, Amber D. Manfree, Josué Medellín-Azuara, Brett Milligan, and Peter Moyle

Droughts are common in California. The drought of 2012-2016 had no less precipitation and was no longer than previous historical droughts (Figure 1), but came with record high temperatures (Figure 2) and low snowpack (Figure 3), which worsened many drought impacts. Water supplies for agriculture and urban users statewide struggled to meet water demands. Conservation and rationing, increased groundwater pumping and a diversified economy helped keep California’s economy robust in most sectors. The drought degraded environmental conditions in the Sacramento-San Joaquin Delta (Delta) as the region became saltier and warmer, invasive weeds spread, and iconic fishes like salmon and Delta smelt had strong declines.

Water demands on the Delta often outstrip its capacity, even in wetter than average years. During the drought, water-demand conflicts increased among human and environmental uses. For example, maintaining Delta outflow and freshwater standards was important to agriculture, drinking water supplies and some sensitive species. To fulfill these downstream needs, upstream water releases from Shasta Reservoir depleted the cold-water pool in 2014 and 2015, increasing Sacramento River temperatures and nearly extinguishing two cohorts of winter-run Chinook salmon.

Figure 1. Cumulative precipitation for water years 2012-2016, compared to average and driest water years (Source: CDEC)

Figure 2. California Mean annual temperature relative to the 20^th Century mean (Source: NOAA National Centers for Environmental Information)

Figure 3. California mean April 1 snowpack at Donner relative to the 20^th Century mean (Source: CDEC)

To help understand scientific aspects of Delta management during the drought, we reviewed official documentation, reports and data, and spoke with numerous agency managers and scientists (Durand et al. 2020).  State and federal water management priorities for the Delta watersheds were to (1) provide essential human health and safety needs, (2) control saltwater intrusion in the Delta, (3) maintain reservoir capacity, and (4) protect at-risk species. Support for these priorities included reducing reservoir releases, Delta export pumping, and Delta outflow; installing an in-Delta salinity barrier; conserving urban water; reducing agricultural water allotments; increasing salmon hatchery production and trucking; and removing invasive aquatic weeds.

These actions helped maintain the Delta’s environment and its dependent uses.  However, with the exception of a study on the effects of the emergency salinity barrier in the Delta, managers were too occupied with emergency-related responsibilities to apply organized scientific methods to learn and prepare for future droughts.  Our main recommendation is to use the lessons of this drought—and the next—to prepare for the one after that. Indeed, 2020 is another dry year and we may already be in a long-term western US megadrought that will force changes in water policy (Williams et al. 2020). The more we can learn from current and future efforts, the better prepared we will be.

Systematic science-based and stakeholder-inclusive preparation for our future needs to continue despite other pressing priorities. The impacts of the COVID-19 pandemic, related economic hardship, and racial/social injustice are all worsened without effective resource management in our drying, warming climate. The availability of data from long-term monitoring of water quality, plankton and fish populations provide insights when extreme wet and dry periods are compared. Each drought in California’s history has brought changes in water management and policy. As the climate changes, drought effects will become more severe and policies are likely to become rapidly outdated.

We suggest preparing today for anticipated increases in frequency and severity of drought years with the following recommendations:

1. Pre-drought warnings. Drought timing differs across California’s regions. The Governor’s declaration of drought emergency in 2014 helped solidify a unified response. Preliminary declarations allow diverse water jurisdictions to examine local conditions, and prepare for potential water supply disruptions.
2. Independent Evaluation. Independent review of water agency data by an interdisciplinary group, such as the Interagency Ecological Program can help managers synthesize and make more environmentally-effective, science-based decisions.
3. Transparency and Documentation. The internet is a cluttered, unstable place. Recent mandates that support data and policy transparency have increased the clutter, and work at odds to the original intent. For online information to be transparent, professional archivists are needed to ensure that documents and data remain available over time, and do not become dead links.
4. Scientific Preparation. Drought response often overrode scientific opportunity. The demands on agencies were enormous. Some surveys increased frequency or were extended to monitor drought effects. But to answer long-term questions about the effects of the changing California climate (including droughts), more systematic, science-based  planning is essential.
5. A Delta drought plan would help managers across agencies organize and prepare resources for the next drought, which might already be beginning. A Delta drought plan should provide a summary of lessons from previous droughts; data analysis; protocols for interagency communication and response; resource deployment and operational contingency plans, with funding and staffing details; and structure to organize a scientific team.
6. Salinity Barriers. The 2015 Delta salinity barrier program was effective and run like an experiment. Managers should prepare to implement solutions with a similar approach, preparing permits, operational coordination, and scientific monitoring in advance.
7. Ecosystem Resilience. Vulnerable animal populations become more threatened during droughts. Interventions are less costly and more effective during inter-drought periods. If vulnerable fish stocks and restored habitats are not materially improved between droughts, they are at risk of failing during the next drought.
8. Salmon hatcheries mostly help to support commercial fisheries, while harming the gene pool of wild stocks, reducing their ability to adapt to changing conditions. This conflict is exacerbated during droughts. More research and a re-thinking of hatchery management is required to separate the needs of competing interests in order to preserve California’s declining salmon heritage, which becomes more vulnerable with each drought.
9. Climate Change. Preparations must be made for the new California climate: hotter, less snowpack, and with more variable and extreme precipitation. A shift to groundwater storage reliance is taking place and may be helpful in the long term. This will affect the timing and volume of water transport in the Delta, and management responses to emerging stressors.

California’s 2012-2016 drought was practice for future climate change events. The whiplash events of drought followed by flood (e.g., 2017 water year) are unlikely to remain exceptional. In the past century, each drought has brought improvements in water systems and drought management, but at a steep price to environmental conditions in the Delta and its watershed. The shifting climate will exacerbate this trend. Relative to economic, cultural and environmental losses, organized science is cheap. Investing in research can make policy discussions and water investment more effective. A proactive organized campaign to understand and anticipate the changing impact of drought on the Delta and California will help mediate future conflicts and preserve California’s rich natural resources.

Further Reading

Dettinger M, Anderson J, Anderson M, Brown LR, Cayan D, Maurer E. 2016. Climate Change and the Delta. San Franc Estuary Watershed Sci. 14(3). [accessed 2017 Feb 2]. http://escholarship.org/uc/item/2r71j15r.

Durand JR, Bombardelli F, Fleenor WE, Henneberry Y, Herman J, Jeffres C, Leinfelder–Miles M, Lund JR, Lusardi R, Manfree AD, et al. 2020. Drought and the Sacramento-San Joaquin Delta, 2012–2016: Environmental Review and Lessons. San Franc Estuary Watershed Sci. 18(2). doi:10.15447/sfews.2020v18iss2art2. [accessed 2020 Jul 17]. https://escholarship.org/uc/item/6hq949t6.

Lund J, Medellin-Azuara J, Durand J, Stone K. 2018. Lessons from California’s 2012–2016 Drought. J Water Resour Plan Manag. 144(10):04018067. doi:10.1061/(ASCE)WR.1943-5452.0000984.

Mount J, Gray B, Chappelle C, Gartrell G, Grantham T, Moyle P, Seavy N, Szeptycki L. 2017. Managing California’s Freshwater Ecosystems: Lessons from the 2012-16 Drought. San Francisco, CA: PPIC.

Williams AP, Cook ER, Smerdon JE, Cook BI, Abatzoglou JT, Bolles K, Baek SH, Badger AM, Livneh B. 2020. Large contribution from anthropogenic warming to an emerging North American megadrought. Science. 368(6488):314–318. doi:10.1126/science.aaz9600.

The authors participated in this review of Delta management and science during California’s 2012-2016 drought, from a variety of institutions including UC Davis, UC Cooperative Extension, UC Merced, and the Delta Stewardship Council Science Program (which also provided funding).  We thank the many agency staff and stakeholders who participated in this process.