Abstract A proper prediction of the water table (WT) depth in hydrological models highly depends on the accuracy of evapotranspiration (ET) estimation. In this study, the response of WT fluctuations to changes in ET was investigated involving the DRAINMOD water management model. The WT depth data were measured during three canola growing seasons (2011-12, 2015-16 and 2016-17) in a paddy field with two subsurface drainage systems (drain depth of 65 cm with two spacing of 15 m and 30 m) in the north of Iran. For the growing seasons, ET was estimated through 17 equations including five temperature- based, four radiation- based, three pan evaporation- based, four combination- based and one mass transfer- based equations. The estimated ET values was then applied in the calibrated DRAINMOD model to simulate the corresponding WT depths in the drainage systems. The reliability of various ET estimation methods and the model predictions were evaluated using determination coefficient (R2), root mean square error (RMSE), error percentage (PE) and mean absolute deviation (MAD). Compared to the FAO- Penman-Monteith equation, the FAO-24 radiation (R2 = 0.90, RMSE = 0.31 mm d-1, MAD =0.71 mm d-1 and PE = - 0.95%), Blaney- Criddle (R2 = 0.93, RMSE = 0.38 mm d-1, MAD =0.76 mm d-1 and PE = - 6.24%), Irmak (R2 = 0.87, RMSE =0.87 mm d-1, MAD =0.41 mm d-1 and PE = - 11.09%) and FAO- 24 pan (R2 = 0.86, RMSE =0.45 mm d-1, MAD =0.80 mm d-1 and PE = - 16.18%) provided the best estimations of ET. However, the best prediction of the WT depths were obtained for the Rohwer and pan evaporation- based equations. These methods considerably improved the reliability of the DRAINMOD predictions in comparison with the Thornthwaite method which is a default method for ET calculation in the model. Based on the results, the Rohwer and FAO-24 pan equations are recommended as suitable methods for estimating ET in the DRAINMOD model for the study area.

中文翻译：

---

使用 DRAINMOD 模型分析地下水位深度波动对蒸散的响应

摘要 水文模型中地下水位（WT）深度的正确预测在很大程度上取决于蒸散量（ET）估计的准确性。在这项研究中，涉及 DRAINMOD 水管理模型研究了 WT 波动对 ET 变化的响应。WT 深度数据是在三个油菜生长季节（2011-12、2015-16 和 2016-17）期间在具有两个地下排水系统（排水深度为 65 cm，两个间距为 15 m 和 30 m）的稻田中测量的。伊朗北部。对于生长季节，ET通过17个方程估算，包括5个基于温度的方程，4个基于辐射的方程，3个基于蒸发的方程，4个基于组合的方程和1个基于传质的方程。然后将估算的 ET 值应用于校准的 DRAINMOD 模型，以模拟排水系统中相应的 WT 深度。使用决定系数 (R2)、均方根误差 (RMSE)、误差百分比 (PE) 和平均绝对偏差 (MAD) 评估各种 ET 估计方法和模型预测的可靠性。与 FAO-Penman-Monteith 方程相比，FAO-24 辐射（R2 = 0.90，RMSE = 0.31 mm d-1，MAD =0.71 mm d-1 和 PE = - 0.95%），Blaney-Criddle（R2 = 0.93 , RMSE = 0.38 mm d-1, MAD =0.76 mm d-1 和 PE = - 6.24%), Irmak (R2 = 0.87, RMSE =0.87 mm d-1, MAD =0.41 mm d-1 和 PE = - 11.09 %) 和 FAO-24 pan (R2 = 0.86, RMSE =0.45 mm d-1, MAD =0.80 mm d-1 and PE = - 16.18%) 提供了对 ET 的最佳估计。然而，WT 深度的最佳预测是通过基于 Rohwer 和 pan 蒸发的方程获得的。与模型中 ET 计算的默认方法 Thornthwaite 方法相比，这些方法大大提高了 DRAINMOD 预测的可靠性。根据结果​​，推荐 Rohwer 和 FAO-24 泛方程作为估算研究区 DRAINMOD 模型中 ET 的合适方法。