Evapotranspiration from a stand of saltcedars

Abstract

A comprehensive study to determine the application, reliability and efficiency of aerodynamic and energy budget methods in computing evapotranspiration during September and October 1962 over a stand of saltcedars at Buckeye has been done. Computed evapotranspiration is evaluated against evapotranspiration measured through water budget control and compared with that obtained by climatological methods. Conclusions: 1. Average evapotranspiration rates computed by aerodynamic, energy budget and climatological methods are respectively +20%, -3 to +8% and +5% of the measured evapotranspiration rates. 2. Mass-transfer equations which are generalized for stability and instability cannot be applied in the present situation. 3. The Thornthwaite-Holzrnan equation in adiabatic form promises good results for calculating evapotranspiration over a period of a day or so. 4. The Bowen ratio method has given the best results with KH/KV=0.53. 5. The energy budget method yields more consistent results than the aerodynamic method. Recommendations: 1. Hourly measurements of the water consumption should be made and a range of the values of 'constants B1 and δ1 in Rossby and Deacon's approaches should be examined against stratified conditions. 2. Using hourly measurements of water consumption the ratio under KH/KV different conditions of stability should be further examined. 3. Climatological methods have yielded good results and should be tried as a control.