UC Merced

The multi-billion-dollar agriculture industry of California's San Joaquin Valley relies heavily on irrigation, which is influenced by hydro-climatological processes varying across time and space. This sector faces significant challenges in water availability due to droughts, regulatory changes, and land conversions, which are expected to worsen with climate change. These factors create uncertainties in understanding future water demand, availability, and resource planning. There is a need for a comprehensive examination of the combined effects of climate change and elevated CO2 on understudied crops, the seasonal variability in water demand and supply, and the long-term impacts of land repurposing on water conservation. This dissertation addresses these uncertainties and fills research gaps related to the impact of climate change on agriculture and water management in the region. The research first explores how climate change and elevated atmospheric CO2 affect water use and phenology in almonds and pistachios, two significant water-consuming yet understudied crops. The results suggest notable changes in phenology, irrigation needs, and reveal their vulnerabilities to climate change. Next, the study scales to seven major crops to investigate the future water demand-supply gap in SJV agriculture at basin scales. The outcomes reveal a widening demand-supply gap for water during critical crop growth stages, particularly highlighting the susceptibility of perennial crops, and emphasizing the need for basin-scale management strategies. Finally, the research evaluates proposed conservation strategies through land repurposing under climate change scenarios. The findings demonstrate the effectiveness of land repurposing strategies in reducing water demand, with habitat restoration and groundwater recharge showing the highest potential for water savings, particularly for perennial crops like almonds. Future studies may explore long-term impacts and economic implications of the proposed adaptive strategies, including the integration of advanced irrigation technologies and crop selection based on climate resilience. These studies provide a comprehensive understanding of how climate change will affect water use in SJV agriculture and provide insights for developing adaptive strategies to implement sustainable water management and agricultural productivity in the region.