Exploring the Role of Man-made and Natural Storage in the Drought Resilience of Two Semi-arid Catchments

Abstract:

Semi-arid regions have long been home to growing cities and expanding agriculture made possible by human infrastructure. As the demands on water systems have grown, and the impacts of climate change have accelerated over the last several decades, these regions are under particular risk for more frequent and severe droughts with slower recovery times. This study focuses on two characteristic semi-arid regions, the Central Valley (CV) in California and the Heihe River Basin (HRB) in China. These two sites were selected due to their similar climates and demands on water systems, but differing quantities and usage of natural and man-made storage reservoirs. Storage reservoirs considered include groundwater aquifers, surface water reservoirs, snowpack and glaciers. This study uses historic datasets to explore how these storage reservoirs are used during drought and how differences in their usage contribute to recovery and resilience. For example, both regions have large irrigated agricultural systems and populations to support which rely on both surface and groundwater. However, the CV has more extensive surface water storage and delivery infrastructure, as well as pumping greater amounts of groundwater over a longer period of time. The HRB on the other hand has a melting glacial water source, different crop choice and historically less groundwater pumping. In both basins the importance of groundwater increases during droughts. Thus, the role of groundwater storage in the drought response of both human and natural systems is further explored using an integrated hydrologic model of the HRB. Various scenarios using ParFlow as the modeling system are run to examine storage changes under different climate and management regimes. Our analysis highlights the variable roles of different storage reservoirs and how they contribute to a watershed’s response to drought.