Using SEBAL Model and HJ Satellite Data to Calculate Regional Evapotranspiration and Irrigation Water Use Efficiency

Abstract

【Objective】 Irrigation water use efficiency is an important parameter to evaluate agricultural water usage efficiency, but traditional methods to measure it were tedious and costly. This paper aims to present an efficient method to estimate regional crop evapotranspiration (ET) and irrigation water use efficiency based on remote sensing imageries. 【Method】 We took the Yichang sub-irrigation district in Hetao irrigation district in Inner Mongolia as an example, and the HJ satellite imageries were preprocessed to identify the planted areas of wheat (Triticum aestivum L.), maize (Zea mays L.) and sunflower (Helianthus annuus L.) using the decision tree method with supervised classification. These data were used to develop a surface energy balance algorithm for the land model (SEBAL) based on the platform of ENVI and IDL, as well as the digital elevation model (DEM) and Landsat data, to estimate ET for each crop from 2013 to 2017. Irrigation water use efficiency during this period was evaluated using rainfall, irrigation, and groundwater data measured in the district. 【Result】 The relative errors of the classification were less than 5% for the sunflower and less than 20% for the wheat and summer maize. The ET calculated from the SEBAL model was accurate with an average relative error of less than 5%, indicating that remote sensing imageries with high spatiotemporal resolution significantly improved ET estimation. The ET of maize, sunflower, and wheat was >600 mm, 500 mm and 450 mm respectively. The irrigation water use efficiency calculated using meteorological data, irrigation and drainage data varied between 0.427 and 0.572 with an average of 0.492 for Yichang sub-district, and between 0.447 to 0.688 with an average of 0.516 for Yonglian sub-district. 【Conclusion】 The SEBAL model is efficient and accurate for estimating regional ET and calculating irrigation water use efficiency. The average groundwater recharge in the study area was 52.13 mm, accounting for 3%~7% of total irrigation water. Without considering groundwater recharge could result in a 0.03~0.08 error in calculating irrigation water use efficiency. There was no noticeable difference in irrigation water use efficiency between the two study sub-districts of different scales.

Keywords

• irrigation water use efficiency
• sebal model
• hj satellite
• regional evapotranspiration