基于SEBAL模型和环境卫星的区域蒸散发量及灌溉水利用系数估算研究

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

【目的】探索基于遥感技术建立准确快捷评估区域蒸散发量和灌溉水利用系数的方法。【方法】以河套灌区义长灌域为研究区,基于SEBAL(Surface Energy Balance Algorithm for Land)模型和较高时空分辨率的环境卫星影像,建立了SEBAL遥感蒸散发估算模型,并与降水量、灌水量和地下水位数据结合,计算了研究区的灌溉水利用系数。【结果】SEBAL模型反演的作物蒸散发量的平均绝对误差在5%以内;2013—2017年研究区灌溉水利用系数在0.427~0.572之间,平均值0.492,高于河套灌区的平均水平。人民支渠区的灌溉水利用系数在0.447~0.688之间,均值为0.516。研究区地下水补给量均值为52.13 mm,约占灌水量的3%~7%,忽略地下水补给量会对灌溉水利用系数准确计算带来0.03~0.08的误差。【结论】基于SEBAL遥感蒸散发模型快速测算了灌溉水利用系数,计算结果具有较好的精度和可信度。模型尺度差异性较小,在不同空间尺度的适用性较好。

【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.