GroMoPo Metadata for Lower Var Valley model

Integrated hydrodynamic modelling is an efficient approach for making semi-quantitative scenarios reliable enough for groundwater management, provided that the numerical simulations are from a validated model. The model set-up, however, involves many inputs due to the complexity of both the hydrological system and the land use. The case study of a Mediterranean alluvial unconfined aquifer in the lower Var valley (Southern France) is useful to test a method to estimate lacking data on water abstraction by small farms in urban context. With this estimation of the undocumented pumping volumes, and after calibration of the exchange parameters of the stream-aquifer system with the help of a river model, the groundwater flow model shows a high goodness of fit with the measured potentiometric levels. The consistency between simulated results and real behaviour of the system, with regard to the observed effects of lowering weirs and previously published hydrochemistry data, confirms reliability of the groundwater flow model. On the other hand, accuracy of the transport model output may be influenced by many parameters, many of which are not derived from field measurements. In this case study, for which river-aquifer feeding is the main control, the partition coefficient between direct recharge and runoff does not show a significant effect on the transport model output, and therefore, uncertainty of the hydrological terms such as evapotranspiration and runoff is not a first-rank issue to the pollution propagation. The simulation of pollution scenarios with the model returns expected pessimistic outputs, with regard to hazard management. The model is now ready to be used in a decision support system by the local water supply managers.集成水文动力模型（Integrated hydrodynamic modelling）是一种高效手段，可使半定量情景足够可靠以支撑地下水管理，前提是数值模拟（numerical simulations）基于经过验证的模型（validated model）。然而，由于水文系统（hydrological system）与土地利用（land use）均存在复杂性，模型构建（model set-up）涉及诸多输入项。以法国南部瓦尔河谷下游的地中海冲积无压含水层（Mediterranean alluvial unconfined aquifer）为案例研究对象，可用于测试一种估算城市背景（urban context）下小型农场未记录取水量（undocumented pumping volumes）的方法。通过对该未记录抽水量的估算，并借助河流模型（river model）校准河-含水层系统（stream-aquifer system）的交换参数后，地下水流模型（groundwater flow model）与实测测压水位（potentiometric levels）的拟合优度（goodness of fit）较高。模拟结果与系统实际行为之间的一致性——针对降低堰坝的观测效应以及此前已发表的水文地球化学数据（hydrochemistry data）——验证了该地下水流模型的可靠性。另一方面，输运模型（transport model）的输出精度可能受诸多参数影响，其中多数参数无法通过野外实测获取。在本案例研究中，河-含水层补给为主要控制因素，直接补给（direct recharge）与地表径流（runoff）之间的分配系数（partition coefficient）对输运模型输出无显著影响，因此蒸散发（evapotranspiration）与地表径流等水文项的不确定性并非污染迁移（pollution propagation）的首要影响因素。利用该模型开展污染情景模拟，所得结果在灾害管理层面呈现出预期的保守性输出。目前该模型已可供当地供水管理者纳入决策支持系统（decision support system）中使用。