On assesssing water supply availability, land idling and economic impacts of agricultural droughts: Cases studies from recent California climate extremes

Climate extremes bring both challenges and opportunities for increasing resilience in agriculture and communities. Drought impact assessments are useful to identify systemwide vulnerabilities and downstream effects from water shortages to agriculture, and aid governments, irrigation user organizations and farmers in both short-term response and planning. The recent climate extremes in California, USA over the past 2012-2022 decade provide a useful case study as one of the largest irrigated agricultural systems which are applicable to other semi-arid areas in the world. We present a framework to gather water supply availability for irrigation in California’s large and complex water supply system, estimate idle land, potential cropping patterns response and economic costs to irrigated agriculture, downstream food processing sectors and regional economies. Recent groundwater regulation forcing sustainable pumping rates at a local level bring additional challenges to cope with water scarcity. We employ regional water balances which consider diverse water supply portfolios for agriculture, remote sensing, and economic models which estimate profit-maximizing crop response and economic costs of water shortages to agriculture and related sectors. We also discuss data challenges in quantifying ultimate impacts of low precipitation, surface water reserves and groundwater restrictions, in a highly engineered and diversified water supply system.  Estimated impacts on agriculture and regionwide income and employment from the 2012-2016 and the more recent 2019-2022 drought in California are discussed along with insights for short-term response, and longer-term water management, planning and policy.