Using satellite-based estimates of evapotranspiration and groundwater changes to determine anthropogenic water fluxes in land surface models

摘要

Irrigation is a widely used water management practice that is often poorlyparameterized in land surface and climate models. Previous studies haveaddressed this issue via use of irrigation area, applied water inventorydata, or soil moisture content. These approaches have a variety of drawbacksincluding data latency, accurately prescribing irrigation intensity, and alack of conservation of water volume for models using a prescribed soilmoisture approach. In this study, we parameterize irrigation fluxes usingsatellite observations of evapotranspiration (ET) compared to ET from a suiteof land surface models without irrigation. We then incorporate the irrigationflux into the Community Land Model (CLM) and use a systematictrial-and-error procedure to determine the ground- and surface-waterwithdrawals that are necessary to balance the new irrigation flux. Theresulting CLM simulation with irrigation produces ET that matches themagnitude and seasonality of observed satellite ET well, with a meandifference of 6.3 mm month?1 and a correlation of 0.95. Differencesbetween the new CLM ET values and satellite-observed ET values are alwaysless than 30 mm month?1 and the differences show no pattern withrespect to seasonality. The results reinforce the importance of accuratelyparameterizing anthropogenic hydrologic fluxes into land surface and climatemodels to assess environmental change under current and future climates andland management regimes.