Evapotranspiration (ET) is an important hydrological variable for better irrigation management, water budgeting, and runoff estimation which should be estimated as precisely as possible both in space and time. However, most of the available crop coefficient-based ET computation methods provide point-scale estimates which need upscaling to apply at the catchment or command area scale. This study evaluates the applicability of the simplified surface energy balance index (S-SEBI) method to compute the spatially distributed daily ET in the Kangsabati reservoir command in eastern India considering the crop coefficient-based coupled Hargreaves–Samani (ETc_HG) method as the benchmark. The study is based on two major crops of paddy and potato in the Rabi season of 2015 at 100 surveyed ground truth locations in the selected command area having different crop growth stages and using the site-specific Landsat 8 images on three cloud-free dates. The S-SEBI method shows improved ET estimates during the crop development stage characterized by higher canopy cover than that during the initial crop development stage with lesser canopy cover that traps less radiation. Results revealed that S-SEBI-based ET estimates correlated well with ETc_HG with r and RMSE value of 0.06 and 1.13 mm/day (initial stage), 0.71 and 0.52 mm/day (development stage) and 0.77 and 0.52 (maturity stage) for paddy. The r and RMSE value for potato is found to be better during the development stage (0.43, 0.69 mm/day) than the initial stage (0.17, 0.64 mm/day) in a similar trend with paddy. Therefore, the crop coefficient-based method could be advantageous at point-scale with adequate data availability conditions, whereas the S-SEBI method could be used in data-scarce areas to estimate the spatially distributed ET values.

中文翻译：

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使用 Landsat 8 影像估算康萨巴蒂水库指挥部实际蒸散量的简化表面能平衡指数 (S-SEBI) 方法评估

蒸散 (ET) 是改善灌溉管理、水资源预算和径流估算的重要水文变量，应尽可能在空间和时间上进行估算。然而，大多数可用的基于作物系数的 ET 计算方法提供点尺度估计，需要放大以应用于集水区或指挥区尺度。本研究以基于作物系数的耦合 Hargreaves-Samani (ETc_HG) 方法为基准，评估了简化表面能量平衡指数 (S-SEBI) 方法在计算印度东部康萨巴蒂水库命令空间分布的每日 ET 的适用性. 该研究基于 2015 年拉比季节的两种主要稻谷和马铃薯作物，在选定的指挥区内具有不同作物生长阶段的 100 个调查地面实况位置，并在三个无云日期使用特定地点的 Landsat 8 图像。S-SEBI 方法显示了作物发育阶段的 ET 估计值有所提高，其特征是冠层盖度高于作物发育初始阶段，冠层盖度较小，捕获的辐射较少。结果表明，基于 S-SEBI 的 ET 估计与 ETc_HG 相关性良好，r 和 RMSE 值为 0.06 和 1.13 毫米/天（初始阶段）、0.71 和 0.52 毫米/天（发展阶段）以及 0.77 和 0.52（成熟阶段）稻田。发现马铃薯的 r 和 RMSE 值在发育阶段 (0.43, 0.69 mm/day) 比初始阶段 (0.17, 0. 64 毫米/天）与稻谷的趋势相似。因此，基于作物系数的方法在具有足够数据可用性条件的点尺度上可能是有利的，而 S-SEBI 方法可用于数据稀缺地区来估计空间分布的 ET 值。