Sensitivity of evapotranspiration of cotton and sorghum in west Texas to changes in climate and CO2

In regions such as west Texas where water is scarce, changes in the water balance may have a significant impact on agricultural production and management of water resources. We used the mechanistic soil-plant-atmosphere simulation model ENWATBAL to evaluate changes in soil water evaporation (E) and transpiration (T) in cotton and grain sorghum that may occur due to climate change and elevated CO2 in west Texas. Climatic and plant factors were varied individually, and in combination, to determine their impact on E and T. Of the climatic factors, E was most sensitive to changes in vapor pressure, and T to changes in irradiance. Simulations suggest that if warming is accompanied by higher humidity, the impact of climate change may be minimal. However, if the climate becomes warmer and less humid, ET may increase substantially. Simulations also suggest that enhanced growth due to elevated CO2 may have a greater impact on ET than climatic change.