Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California

California's climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US This, combined with chronic groundwater overdraft of 0.6-3.5 km3 yr-1, creates the need to identify additional surface water sources available for groundwater recharge using methods such as agricultural groundwater banking, aquifer storage and recovery, and spreading basins. High-magnitude streamflow, i.e. flow above the 90th percentile, that exceeds environmental flow requirements and current surface water allocations under California water rights, could be a viable source of surface water for groundwater banking. Here, we present a comprehensive analysis of the magnitude, frequency, duration and timing of high-magnitude streamflow (HMF) for 93 stream gauges covering the Sacramento, San Joaquin and Tulare basins in California. The results show that in an average year with HMF approximately 3.2 km3 of high-magnitude flow is exported from the entire Central Valley to the Sacramento-San Joaquin Delta often at times when environmental flow requirements of the Delta and major rivers are exceeded. High-magnitude flow occurs, on average, during 7 and 4.7 out of 10 years in the Sacramento River and the San Joaquin-Tulare Basins, respectively, from just a few storm events (5-7 1-day peak events) lasting for 25-30 days between November and April. The results suggest that there is sufficient unmanaged surface water physically available to mitigate long-term groundwater overdraft in the Central Valley

The California drought: Coping responses and resilience building

Building resilience to extreme events is very complex. It involves consideration of climatic and non-climatic factors, human and natural environments and their dynamics, and governance systems that include groups with wide-ranging authorities, influence and interests. In this article, we analyse the effects of the latest multi-year drought (2011–2016) in agricultural production in California; impacts on food security; and coping responses of several actors. We found that despite the drought and water shortages, California continued to be the leading state for fruit and tree nuts and that it did not affect food security. We also found that these results were strongly influenced by the numerous policy, regulatory, institutional, and management decisions taken at the local, state and federal levels, as well as to availability of groundwater, the primary drought reserve. The California case can be considered an example for the rest of the country, and the world, that extreme events require extraordinary preparedness and response measures just to cope with them, not to mention adapting to them, and that building resilience is a long-term process