Abstract
Abstract. The current generation of large-scale hydrological models does not include a groundwater flow component. Large-scale groundwater models, involving aquifers and basins of multiple countries, are still rare mainly due to a lack of hydro-geological data which are usually only available in developed countries. In this study, we propose a novel approach to construct large-scale groundwater models by using global datasets that are readily available. As the test-bed, we use the combined Rhine-Meuse basin that contains groundwater head data used to verify the model output. We start by building a distributed land surface model (30 arc-second resolution) to estimate groundwater recharge and river discharge. Subsequently, a MODFLOW transient groundwater model is built and forced by the recharge and surface water levels calculated by the land surface model. Results are promising despite the fact that we still use an offline procedure to couple the land surface and MODFLOW groundwater models (i.e. the simulations of both models are separately performed). The simulated river discharges compare well to the observations. Moreover, based on our sensitivity analysis, in which we run several groundwater model scenarios with various hydro-geological parameter settings, we observe that the model can reasonably well reproduce the observed groundwater head time series. However, we note that there are still some limitations in the current approach, specifically because the offline-coupling technique simplifies the dynamic feedbacks between surface water levels and groundwater heads, and between soil moisture states and groundwater heads. Also the current sensitivity analysis ignores the uncertainty of the land surface model output. Despite these limitations, we argue that the results of the current model show a promise for large-scale groundwater modeling practices, including for data-poor environments and at the global scale.
Highlights
Groundwater is a vulnerable resource, and in many areas, groundwater is being consumed faster than it is being naturally replenished (e.g. Rodell et al, 2009; Wada et al, 2010)
The model may not be suitable for karstic aquifer areas – for which MODFLOW
Is not suitable for modeling groundwater flow – PCRGLOBWB-MOD can be applied in several areas that contain large sedimentary basins or pockets, such as the basins of Nile, Danube, Mekong, Yellow and Ganges-Brahmaputra Rivers
Summary
Groundwater is a vulnerable resource, and in many areas, groundwater is being consumed faster than it is being naturally replenished (e.g. Rodell et al, 2009; Wada et al, 2010). Given increased population and heightened variability and uncertainty in precipitation due to climate change, the pressure upon groundwater resources is expected to intensify These issues make monitoring and predicting groundwater changes, especially over large areas, imperative. Some existing large-scale groundwater models, such as in the Death Valley area, USA (D’Agnese et al, 1999), and in the MIPWA region, the Netherlands (Snepvangers et al, 2007), were developed on the basis of highly detailed information (e.g. elaborate 3-D geological models). Such information may be available in developed countries but is seldom available in other parts of the world
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