Controlled drainage (CD) has emerged as an effective strategy to prevent field waterlogging and mitigate drought during crop growth by altering the hydrological process, while few studies have quantified its effect on groundwater-surface water interactions and groundwater recharge at a regional scale. In this study, a new model is developed for the coupled numerical simulation of water flow in ditches, soil, and underground aquifers under CD conditions. The domain is partitioned into horizontal sub-areas and two vertical layers, with ditches discretized into segments based on groundwater flow grids. The Saint-Venant equations, Richards equation, and MODFLOW are applied to describe water movement processes in ditches, soil, and underground aquifers, respectively. The proposed model is calibrated and validated using five years of observations of ditch water levels (DWL) and groundwater levels, demonstrating excellent agreement with observed data. Subsequently, water balance components of the shallow aquifer below 1 m depth (GW), 1 m of root layer soil profile (SW), and ditch water (DW) under seven scenarios with different control schemes during flood and dry seasons are analyzed to quantify variations in hydrological processes caused by CD. The results show that CD significantly impacts water within SW, GW, and DW, soil evaporation, infiltration, and net recharge from GW to SW (GtoS) by altering regional groundwater table depth (GWT) through the exchange between DW and GW (DtoG and GtoD). GWT and DW show moderate correlation with GtoD, while their correlation with DtoG varies significantly under different rainfall conditions. Smaller precipitation results that precipitation and GWT have a higher linear correlation with water balance components during the dry season compared to the flood season. The correlation values (r) between transpiration (T) and GWT range from −0.99 to 0.96 and −1 to −0.85 during the flood and dry seasons, respectively, indicating a pronounced influence of CD on crop growth. On average, a 1 m increase in DWL control scheme leads to a 0.51 m increase in DWL, and regional GWT decreases by 0.35 m and 0.24 m during flood and dry seasons, respectively. Furthermore, for every 1 m decrease in GWT, net GtoS increases by 36.1 mm and 28.1 mm, respectively, resulting in an increase in SW by 13.9 mm and 11.8 mm, respectively. Considering the varying main crop water stress and the impact of CD under different rainfall conditions, an appropriate CD scheme needs to be adjusted accordingly. These findings provide a quantitative reference for the effect of CD on regional hydrological process and serve as a typical case for similar areas aiming to implement CD strategies for waterlogging and drought control.

中文翻译：

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受控排水区水文过程和地下水与地表水相互作用的耦合区域尺度数值模型


控制排水（CD）已成为通过改变水文过程来防止田间内涝和缓解作物生长期间干旱的有效策略，但很少有研究量化其对区域范围内地下水-地表水相互作用和地下水补给的影响。在本研究中，开发了一种新模型，用于 CD 条件下沟渠、土壤和地下含水层中水流的耦合数值模拟。该区域被划分为水平分区和两个垂直层，沟渠根据地下水流网格被离散化为多个部分。 Saint-Venant方程、Richards方程和MODFLOW分别用于描述沟渠、土壤和地下含水层中的水运动过程。所提出的模型使用五年来的沟渠水位 (DWL) 和地下水位观测进行了校准和验证，证明与观测数据非常吻合。随后，对汛期和旱季不同控制方案七种情景下1 m以下浅层含水层（GW）、1 m根层土壤剖面（SW）和沟渠水（DW）的水平衡成分进行分析，量化CD 引起的水文过程的变化。结果表明，CD 通过 DW 和 GW 之间的交换（DtoG 和G 到 D）。 GWT和DW与GtoD表现出中等相关性，而与DtoG的相关性在不同降雨条件下变化显着。 降水量较小，导致旱季降水量和 GWT 与水平衡分量的线性相关性高于汛期。洪水期和旱季蒸腾量（T）和GWT之间的相关值（r）分别为-0.99至0.96和-1至-0.85，表明CD对作物生长有显着影响。平均而言，DWL控制方案每增加1 m，DWL增加0.51 m，洪水和旱季区域GWT分别减少0.35 m和0.24 m。此外，GWT 每减少 1 m，净 GtoS 分别增加 36.1 mm 和 28.1 mm，导致 SW 分别增加 13.9 mm 和 11.8 mm。考虑到主要作物水分胁迫的变化以及不同降雨条件下CD的影响，需要相应调整合适的CD方案。这些研究结果为CD对区域水文过程的影响提供了定量参考，并为类似地区实施CD防涝抗旱策略提供了典型案例。