Coupled Groundwater-Surface Water Modeling for Sustainable Groundwater Management

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Mehrdis Danapour
Groundwater is the world’s largest source of accessible freshwater and is crucially important for irrigation, and hence for food security globally. In many regions including Denmark groundwater is the only source of water supply. The society tends to perceive and manage the surface water resources more readily in comparison to the groundwater resources which are hidden and thus more difficult to conceptualize. As a result of growing world population, demand for food, energy, industry and urbanization, in addition to more severe and frequent occurrence of droughts due to climate change, water resources are put under increasing pressure. In the interconnected groundwater-surface water environment, a drop in the groundwater level due to abstractions leads
to decrease of groundwater recharge to streams and alteration of flow regimes. This can potentially have very adverse effects on aquatic ecosystems thus in an integrated and sustainable groundwater approach the link between surface water and groundwater is a matter of utmost concern. With the aid of physically based, dynamically coupled groundwater and surface water the past, current and
future state of water resources as well as implications of management decisions and other imposed changes (such as climate change) in the catchment can be explored and quantified.
The objective of this Ph.D. thesis was to apply a coupled groundwater-surface water hydrologic model for sustainable groundwater management. Special focus was set on an adequate representation of subsurface heterogeneity, roundwater-surface water interaction, and temporal dynamics of hydrological responses at a catchment scale.
The study area is located in the central part of Jutland in Denmark and extends over an area of approximately 4,900 km2. The topography is characterized by a north-south-oriented divide (Jutland Ridge) which corresponds to the maximum advancement of the late Weichselian ice sheet’s front.
The sub-surface geology in this area is characterized with complex glacial formations such as buried valleys. The surface geology in the western side of the Ridge is dominated by Quaternary deposits, mainly consisting of coarse sandy soil whereas the eastern side of the Ridge is dominated by till sediments. Due to the sub-surface geology and high permeability of soil west of the Ridge the
streamflow in this area is mainly groundwater fed and the dominant land use type is agriculture with high irrigation demand.
In order to enhance the physical representation of the system, especially with respect to groundwater flow a regional-scale flow model has been parametrized using Pilot points and geostatistical interpolation method. The model has been calibrated in a multi-objective function framework in which the water balance prediction uncertainty has been quantified with respect to the parameters and observational data worth. The highly parameterized model proved to be successful in terms of meeting different objective functions in addition to estimation of reliable parameters. Moreover, it proved to have exploited the information content available in the existing data set to a higher extent resulting in a more physically meaningful pattern than the model based on a simpler parameterization. The impact of groundwater abstraction on the stream flow alteration has been successfully simulated and evaluated with the coupled groundwater-surface water model.
However, the model grid-size had a significant effect on the model simulated impact on the low flows. The application of empirically-derived ecological indicators combined with the hydrological model indicated a higher degree of vulnerability of aquatic ecosystems in the upstream of the catchment and smaller streams. However, these indicators showed a high degree of complexity when used for the estimation and prediction of groundwater abstraction impact on the stream ecosystems.
A flexible, robust, and yet efficient groundwater optimization framework has been successfully developed by utilizing the transient, distributed nature of a physically based coupled surfacegroundwater model in conjunction with linear programming management optimization algorithm.
The developed optimization framework considers multiple constraints (stream flow criteria at multiple locations) for different management decision variables (e.g. groundwater abstraction for irrigation) at different management scales (from single well to group(s) of well clusters). The combinations of all these techniques have proven to have the potential to guide stakeholders and water resource managers in finding integrated solutions to groundwater-surface water management challenges.
ForlagDepartment of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
Antal sider112
StatusUdgivet - jan. 2020

ID: 239171196