Spatial and Temporal Analysis of Evapotranspiration Using Satellite Remote Sensing Data: A Case Study in the Gezira Scheme, Sudan

Abstract

Current methods for estimating evapotranspiration (ET), the essential variable in irrigation performance and water management, largely neglect the spatial and temporal variations in ET. Accurate regional ET maps would provide valuable information on actual crop water use. The objective of this study was mainly to evaluate a Pilot Project (PP) supported by the Food and Agriculture Organization of the United Nations (FAO). In this study, Surface Energy Balance Algorithm for Land (SEBAL) model was used to assist the evaluation attempt. The performance of the ET model was evaluated by comparing the predicted daily ET with values derived by conventional methods based on ground measurements and meteorological data on 6 Sepetmber, 25 Sepetmber, 28 November and 11 December. The ET values from SEBAL showed good agreement with the actual values measured in the field. The amount of water required to satisfy the irrigation needs at canal level was monitored and successfully estimated. However, during November the daily estimated water demand ranged from 15667 m3 for Tereifi minor to 28954 m3 for Heleiwa west minor canal. The average values of relative irrigation supply (RIS) were determined as 0.73 which indicates improvements in operational performance of minor canals. The results of this study demonstrate that remote sensing measurements and limited ground data can be used to successfully estimate ET and assess irrigation performance in areas of poor infrastructure. Results achieved support previous opinion that repeatedly recommended the PP as a crucial step for water management in the Gezira scheme, Sudan.

Keywords: evapotranspiration, irrigation performance, Gezira scheme, remote sensing, SEBAL