Remote sensing estimation of actual evapotranspiration and crop coefficients for a multiple land use arid landscape of southern Iran with limited available data

The Gareh Bygone Plain is an arid area, south of Zagros Mountains, in Southern Iran, where a floodwater spreading project has been implemented for artificial recharge of groundwater. Knowledge/mapping of actual evapotranspiration for the mainland uses (natural pasture, irrigated crops and tree plantations) is of major importance for water management in this remote area. The Surface Energy Balance System (SEBS) model was used to estimate actual evapotranspiration (ET) using non-cloudy images for 32 dates of Landsat 5 TM from May 2009 to October 2010. Various improvements were required for ET computations, including relative to the very high wind speed observed. Reference ET was computed with observed weather data and SEBS products. Thus, crop coefficients (K_c) were obtained as the ratios of actual to reference ET relative to the main types of vegetation. The mid-season K_c generated with SEBS were compared with those previously obtained in the region and with those published in literature. Consumed water by cultivated crops based on SEBS compared well with applied water measurements. Coherent results were obtained which allow validating the SEBS approach for conditions of limited available data.