Modelling

The regional scale modelling will build on existing modelling efforts and the research will focus on improving boundary conditions, spatial parameterization and model calibration. Regarding boundary conditions, the main challenges are related to estimating the surface and groundwater inflow to the main alluvial aquifers of NCP, estimating the spatial distribution of actual evapotranspiration and groundwater recharge and quantifying groundwater abstractions for irrigation. We will draw upon existing modelling efforts, on surface water modelling in the upstream mountain regions and previous groundwater models in order to obtain better boundary flows of a coupled modelling system of the NCP. In addition, different methods for quantification of groundwater abstraction for irrigation will be investigated. These could include crop growth modelling and satellite remote sensing based methods. Satellite remote sensing data can also be utilized for improved model calibration, by introducing additional and independent data to constrain the model optimization. Data, such as lumped groundwater storage change data from the GRACE satellite and spatially distributed estimates of actual evapotranspiration, will complement traditional observation data such as groundwater head and river discharge data. Other modelling efforts will be centred around field-scale groundwater models, that are consistent with the regional-scale model, but with a refined spatial grid resolution, detailed geological interpretation and higher density of observed data. These site specific models will be set up for the two MAR installations at the Beijing Beiyun River and Jinan Yufuhe River field sites and will be calibrated to local conditions. The regional hydrological model will be an important tool to delineate areas within the NCP most suitable for MAR application and for scenario testing, while the field scale models are essential for predicting long term efficiency of MAR facilities within the NCP. MAR application scenarios, to be developed in collaboration with stakeholders during workshops and meetings, will be designed for hydrological model application and tested through the modelling tools. Aspects to include in scenario development will be location of MAR installations, amounts of reclaimed water to recharge, changes in aquifer storage characteristics etc.