Using Coupled Subsurface-Atmospheric Simulations to Investigate the Impact of Irrigation on Atmospheric Response in the San Joaquin River Basin, California

Abstract:

Observational and modeling studies are continually improving our understanding of terrestrial and atmospheric process interactions over natural and managed systems. Recent studies have implicated irrigation as a strong factor in perturbing land-atmosphere coupling, although the details of this interaction are not fully characterized. Therefore, in this study we seek to better understand the role of subsurface flow under conditions of groundwater extraction and irrigation on resulting atmospheric states. We use an ensemble of coupled ParFlow-WRF simulations over the San Joaquin River Basin in California to identify the type and character of land-atmosphere interactions for a set of irrigation scenarios. Ensemble members include selected boundary layer schemes, land surface model configurations, and initial and boundary condition perturbations. Variability in atmospheric response, particularly in boundary layer height and precipitation patterns, under high water table (characteristic of predevelopment conditions) and lowered water table (resulting from historic groundwater extraction) conditions are evaluated in the context of the uncertainty resulting from choice of model physics and atmospheric perturbations. Hydrologic alterations associated with lowered water table elevation appear linked to the atmosphere via changes in boundary layer height.