by Jay Lund
Droughts and this drought in California
- California has more hydrologic variability than any state in the US, meaning that we have more drought and flood years per average year than any other state. This is a problem, but has also meant that we have designed for droughts, which are always testing us.
- 2021 is the 3rd driest year in more than 100 years of precipitation record. 2020 was the 9th driest year in the precipitation record.
- Much warmer temperatures are further reducing streamflows and aquifer recharge, and has lengthened and deepened the wildfire season.
- Large reductions are occurring in surface water available for agriculture, especially in the San Joaquin Valley, but also in the Sacramento Valley and smaller river valleys statewide.
- Much increased groundwater pumping greatly reduces agricultural impacts, but affects rural wells.
- Major forest and aquatic ecosystem impacts are occurring, especially for wildfires and salmon runs, particularly for winter-run salmon downstream of Shasta Dam.
- A growing number of small communities and towns are being affected, in addition to more common problems for rural household and community wells. Santa Clara Valley (San Jose area) is the most-affected major urban area, seeking 30% water use reductions.
- If next year is also dry, agricultural and environmental impacts will increase and urban impacts will expand.
- Warmer temperatures from climate change are worsening droughts, reducing the amount of precipitation that arrives at reservoirs and aquifers, lengthening wildfire seasons, and worsening conditions for cold-water fish species, such as salmon. We need to further adapt water, land, and environmental management for these changes.
- Another dry year is likely. Very dry watersheds, very low reservoir levels, falling aquifers, and higher temperatures mean more precipitation is needed to make next year not dry.
- Under SGMA, farmers will need to repay additional groundwater pumped during the drought, meaning some reductions in lower-valued crops in wetter years so aquifers can recover to sustain permanent crops in future droughts. Few basins can sustain aquifers with managed aquifer recharge alone; many will need deep reductions in aquifer pumping in wetter years.
- Sizable long-term reductions in irrigated area seem unavoidable in parts of the San Joaquin Valley. Urban water conservation statewide is helpful, and still more conservation will help a bit.
- A more formal state water accounting system is needed to support tighter surface water right administration, SGMA planning and implementation, and environmental uses. Water right curtailments are likely to become routine in more basins.
Arax, Mark (2021), “The Well Fixer’s Warning,” The Atlantic, August 17.
Lund, J.R., J. Medellin-Azuara, J. Durand, and K. Stone, “Lessons from California’s 2012-2016 Drought,” J. of Water Resources Planning and Management, Vol 144, No. 10, October 2018.
Pinter, N., J. Lund, and P. Moyle. “The California Water Model: Resilience through Failure,” Hydrological Processes, Vol. 22, Iss. 12, pp. 1775-1779, 2019.
Jay Lund is Co-Director of the Center for Watershed Sciences and Professor of Civil and Environmental Engineering at the University of California – Davis.