Estimation of Crops Water Consumptions Using Remote Sensing with Case Studies from Egypt

Abstract

Actual evapotranspiration (ETa) represents crop water consumption in consideration, the water conserved in plant tissue structure representing about 1% or less. Many researchers understood the importance of ETa, and they did their best to measure or calculate ETa. Tens of experimental and mathematical models were used to calculate evapotranspiration in last century. Many weather, plant, and soil parameters were inserted in these models. Most of these models were acceptable for local scale and used for certain climate. Only a very few models were used on a global scale but need a lot of parameters and well-distributed weather stations. The crop pattern was the main obstacle to using these models on a large scale. The early satellite age was the beginning of the development of global-scale models through using satellite images to calculate ETa and manage crop water consumption. Triangle and crop water stress index (CWSI) methods were used and developed in the 1970s and the 1980s, respectively. In 1990s and beginning of 2000s, the SEBAL and SEBS models represent a new step in the way of evapotranspiration development models. In the last decade, METRIC, ETLook, Alexi, and ET watch models were developed to fill the gaps of SEBAL and SEBS models. Researchers around the world still try to modify these models to improve the results.