Hydrologic and land-energy feedbacks of agricultural water management practices

Recent studies demonstrate strong interdependence between groundwater dynamics, land surface water and energy fluxes over some regions, including significant negative correlation between latent heat flux and groundwater depth. Other studies show that irrigation increases latent heat flux and decreases the Bowen ratio (ratio of sensible to latent heat flux), with subsequent feedbacks on local and regional climate. We use an integrated hydrologic model to evaluate impacts of groundwater pumping, irrigation, and combined pumping and irrigation on groundwater storage, land surface fluxes, and stream discharge over the Little Washita River watershed in the Southern Great Plains of North America. Pumping and irrigation are shown to impact simulated water and energy fluxes at local and watershed scales, with the magnitude of impacts governed by local water table depth. When pumping and irrigation are combined, irrigation has a dominant impact on spatially distributed surface energy processes while pumping has a dominant impact on basin-integrated hydrologic conditions.