Drought in the Delta: Socio-ecological Impacts, Responses, and Tools

Droughts are frequent events in the western US, and can disrupt water supply and degrade water quality, challenging water management in the Sacramento–San Joaquin Delta. This chapter for the State of Bay–Delta Science report describes what drought means for the Delta, how drought is managed in the Delta, and how drought management has changed over time. Projections of future climate indicate the possibility of increased frequency and severity of droughts, which would increasingly affect California’s water system, society, and ecological functions within and beyond the Delta. California has experienced several major droughts in the 20th and 21st centuries, each of which has caused significant social and ecological effects, and has motivated improvements in water management. Droughts decrease native fish populations, increase harmful algal blooms, and promote the spread of many invasive plant and animal species. For people living within the Delta and those that rely on Delta water exports, droughts increase drinking water costs and decrease agricultural production, negatively affecting agricultural economies and labor markets. Tools developed in response to droughts include actions that increase supply (such as building water infrastructure), actions to reduce demand (such as water-conservation campaigns), and mitigation actions (such as monetary relief for drought-affected impacted communities. Improving drought resilience requires development of additional drought responses, increased forecasting accuracy, and increased awareness of effects on vulnerable communities and ecosystems. Even with development of additional management actions, strategies, and regulations, meeting the current levels of demand for water will likely be difficult. Drought conditions already cause conflict between human and environmental uses, and—with more extreme droughts possible in the future and projected increases in demand—providing for all users’ needs, even with major changes to water management in the Delta, will be challenging.