Spatial and temporal variability analysis of green and blue evapotranspiration of wheat in the Egyptian Nile Delta from 1997 to 2017

Abstract

Assessing green and blue water evapotranspiration (GWET and BWET) is the key to water resources management and improving water productivity. This study focuses on assessing, evaluating and managing evapotranspiration in Egyptian Nile Delta over 1997–2017 for thirteen regions. The monthly data of minimum and maximum temperatures, precipitation and solar radiation from November to May were derived from open access data for calculation of reference evapotranspiration and rainfall accounts. Wheat crop coefficient (Kc) values were estimated using the air temperature and base temperature of crop. GWET and BWET were calculated and mapped for each region in the ArcGIS environment. Land use land cover (LULC) was analyzed during 1997, 2005, 2011, and 2017 using Landsat images. The main findings of the research are as follows: (1) average values of crop coefficients Kc-init, Kc-mid and Kc-end were 0.72, 1.13, and 0.41 through initial, middle, and end growing seasons, respectively; (2) the best regions for saving green and blue water were Sidi-Salim, Bilqas, Ar-Riyad, Al-Hamul, and Biyala; (3) the total water saved was 4.80% and 53.12% of blue and green water accounts; (4) high coefficients of determination between precipitation, GWET, and BWET proportions were 0.99 for both. Furthermore, relative irrigation supply is a good indicator for predicting GWET and BWET with determination coefficients of 0.99 and 0.76, respectively. It can be concluded that the data integration of geographic information and LULC changes is the best way for water management and sustainable agro system development under limited water resources.