The impact of groundwater depletions on groundwater surface water interactions and streamflow across the contiguous US

Abstract:

Over the past 50 years, connections between climate change and streamflow trends have been observed in many regions of the Western US. However, much of the work to detect climate change signals in historical hydrologic records has focused on surface water changes in relatively undeveloped basins. While this is necessary to isolate any climate change signal from uncertain water management operations, it also excludes interactions with the concurrent human development that has occurred over the last 100 years. In highly utilized groundwater systems, such as the High Plains Aquifer, groundwater mining has already been linked to streamflow depletions at local to regional scales; but no prior studies have evaluated the role of groundwater declines in historical changes of groundwater surface water interactions at the continental scale. Here we isolate the influence of groundwater depletions from water management operations (e.g. irrigation and surface water diversions) to systematically evaluate how subsurface storage losses alter large-scale hydrologic interactions. Using a fully integrated groundwater surface water model of the contiguous US we simulate dynamic equilibrium conditions of a predevelopment system and a system with groundwater depletions equivalent to all of the groundwater development of the 20th century. Results illustrate the effect of persistent drawdown on streamflows, recharge and groundwater surface water exchanges across many spatial scales. In addition, we run transient simulations to evaluate the effect of these shifts on seasonal surface water variability. Simulations demonstrate the widespread trends in groundwater surface water interactions that have already resulted from ubiquitous groundwater mining in the United States and the potential for such changes to influence future response to climate variability.