Effects of Wildfire on the Water Balance of the Arid Shrublands in the Western United States

In the western US, intensifying wildfire regimes imply that an increasing fraction of land will exist in a post-fire recovery state at any given time. While much prior work has focused on how forest fires can lead to temporarily suppressed evapotranspiration (ET), few studies have focused on how fire changes the water balance in the shrublands that dominate the arid interior of the western US. There, changes to the water balance are especially important because nearly all precipitation is lost to terrestrial ET, and thus reductions in ET may have especially large effects on streamflow and groundwater recharge. In this presentation, I will show results from a field study in which energy-balance stations in paired post-fire and control plots were used to estimate the relative reduction in ET in the decade following shrubland wildfires; mid-summer ET was often >30% lower in the post-fire plots. I will also show results from a similar analysis at a much greater spatial extent that uses ET values estimated from products developed through NASA’s ECOSTRESS mission; again, these data show reduced ET persisting after wildfires for decades. I will use these findings to discuss the large-scale implications of wildfire on the water balance of the Great Basin region of the western US.