Groundwater-dependent agricultural intensification has led to unsustainability of groundwater systems in many parts of the world. The unconfined aquifers in the Eastern Indo-Gangetic Plains (EIGP) of India are one of the most extensive aquifer systems in South Asia and are prone to ever intensifying agricultural systems. This paper aims at evaluating the long-term impacts of agricultural intensification on groundwater dynamics in an agriculturally important sub-region of EIGP. The study proposes a multi-model approach, combining the capabilities of vadose zone model (HYDRUS-1D) and aquifer simulation model (MODFLOW) to analyse the recharge and discharge mechanisms in the alluvial Gangetic Plains. The study mathematically reconstructed the vadose zone and aquifer geometry and implemented them into flow models. We demonstrate that the loosely coupled vadose zone and groundwater flow modelling framework is highly suitable for simulating the impact of changed cropping intensity on groundwater dynamics. The recharge estimates from HYDRUS-1D and calibration of regional groundwater flow model offered a robust set of parameter values for the prevalent conditions of EIGP. The results show good correspondence between the observed and simulated water table levels during calibration, with RMSE = 0.56–0.59 m, NSE = 0.76–0.99 and R² = 0.83–0.91, all within acceptable limits. Projections showed that although the water table in the region would remain fairly stable under lower levels of cropping intensity (135–150%), further increase to 200 and 300% would lead to water table decline at the rate of 0.87 and 1.83 m per year, respectively. These changes could therefore impact future groundwater risk management in EIGP. This reinforces the view that groundwater-dependent intensification may be sustainable in long term only if adaptation strategies and compensatory measures are adopted.

依赖地下水的农业集约化导致世界许多地区地下水系统不可持续。印度东部印度恒河平原 (EIGP) 的非承压含水层是南亚最广泛的含水层系统之一，并且倾向于不断强化农业系统。本文旨在评估农业集约化对 EIGP 农业重要子区域地下水动态的长期影响。该研究提出了一种多模型方法，结合包气带模型 (HYDRUS-1D) 和含水层模拟模型 (MODFLOW) 的功能来分析冲积恒河平原的补给和排放机制。该研究在数学上重建了包气带和含水层的几何形状，并将它们应用到流动模型中。我们证明松散耦合的包气带和地下水流建模框架非常适合模拟种植强度变化对地下水动态的影响。来自 HYDRUS-1D 的补给估计和区域地下水流模型的校准为 EIGP 的普遍条件提供了一组可靠的参数值。结果显示校准期间观测到的和模拟的地下水位水平之间具有良好的对应关系，RMSE = 0.56–0.59 m，NSE = 0.76–0.99 和R ²  = 0.83–0.91，都在可接受的范围内。预测显示，虽然该地区的地下水位在较低的耕作强度水平（135-150%）下保持相当稳定，但进一步增加到200和300%将导致地下水位以每年0.87和1.83 m的速度下降， 分别。因此，这些变化可能会影响 EIGP 未来的地下水风险管理。这强化了这样一种观点，即只有采用适应战略和补偿措施，依赖地下水的集约化才能长期可持续。