GDrought-related vulnerability and risk assessment of groundwater resources in Belgium
Proposal summary
Proposal summary
Drought can be described as a temporary decrease in water availability over a significant period of time. In contrast to e.g. flooding, which has a direct and visible effect, drought is a creeping natural hazard. In the first place drought is a direct result of deficient precipitation and as such it is mainly a meteorological-related hazard. In case the water shortage affects groundwater bodies the term groundwater drought is used. Groundwater droughts develop slowly but can have considerable socio-economic and environmental effects. Groundwater drought is a complex phenomenon and is hard to identify. To describe groundwater drought three main variables are important: groundwater recharge, groundwater level and groundwater discharge. Groundwater recharge is important as it is the source (inflow) of all groundwater. The groundwater table gives an idea of the storage, while groundwater discharge represents the outflow from the groundwater system.
Next to natural meteorological variations also human induced factors play a role. In the Belgian context the main influencing factors, determining the inflow and potentially resulting in a recharge deficit and an overall deterioration of groundwater resources are: climate, land-use/land cover (LULC) and groundwater demand for human activities. The combined effect of these factors makes that some groundwater bodies are under pressure. In these groundwater bodies the outflow exceeds the inflow generating a reduction in storage and hence an unsustainable situation.
A thorough knowledge of all three influencing factors and their interaction or combined effect is essential for a reliable estimate of the groundwater budget and a sustainable management. Especially because expected changes in climate, land-use and demand are likely to even reinforce these negative effects, having substantial socio-economic and environmental impacts. Hence there is a need for an improved understanding of climate-related and human-induced effects of groundwater drought. This should form the basis for an integrated approach which allows tackling these negative effects and safeguarding sustainability of groundwater resources.
The overall objectives of this project are:
- Increasing policy-relevant understanding of influencing factors (climate-LULC-demand) determining,groundwater drought.
- Obtaining reliable spatially distributed timeseries for groundwater recharge and water table levels, enabling to describe where (space) and when (time) groundwater drought occurred/occurs.
- Assessing the socio-economic and environmental impacts of groundwater drought at a large catchment scale for the present and future situation (coming 30 years).
- Mapping the individual and combined vulnerability of groundwater resources.
- Assessing the risk as a monetary loss in order to enable objective evaluation and reduce the groundwater drought risk towards the future.
- Developing a methodology and supporting quantitative tools aimed at planning and decision support with respect to (ground)water management, applicable at the level of river basins in Belgium and beyond.
- Informing the public, consisting of domain specialists and lay persons about the results of the analysis carried out in the case region, by means of an Internet-based indicator atlas.
In this project a combined water balance and groundwater modelling strategy is applied to obtain a reliable spatially distributed recharge and water table timeseries. The study area is the Dijle and Demer catchment in central Belgium, which correspond more or less with the underlying vulnerable Brulandtkrijt groundwater system.
The first step is a groundwater drought hazard assessment to increase knowledge and understanding of groundwater drought in a Belgian context. Starting point is a thorough analysis of the main influencing factors. Regarding the climate factor, a hydro-meteorological time-series analysis combined with a drought index approach enables the identification and characterization of historical and recent drought hazards. Land-use/land-cover characterization focuses on the estimation and mapping of agricultural land use change and change of impervious fraction cover, which are very sensitive and determining parameters for recharge estimation.
Once the spatially distributed recharge and water table timeseries is obtained the baseline scenario, which represent a sustainable groundwater system, is defined. Using the threshold method the “rules” to maintain the groundwater system sustainable are set. This baseline scenario forms the basis for the final groundwater drought risk assessment.
Based on groundwater simulations the baseline (reference) and current status of agriculture (crop yield), natural ecosystems and water supply are determined. A next step is to study the impact of changing influencing factors on the total system. Readily available socio-economic and climate scenarios (SRES from IPCC) for the future are combined with specific demand scenarios and used in a land-use change model. Using the water balance and groundwater model the individual and overall impact can be assessed, not only on groundwater resources, but also on future agricultural production, natural ecosystem health and water supply. This impact analysis forms the basis for vulnerability mapping for each of the separate aspects.
Finally the baseline scenario (sustainable system) and the defined threshold functions (“rules”) are used in combination with the scenario simulations to determine the separate risk for relevant socio-economic activities (agriculture, industry, etc.) and to represent this risk as a monetary loss. Also a combined risk is calculated using a multi-criteria approach. A loss of ecological values is considered as a limiting factor in the monetary risk calculation. Uncertainty of the influencing factors on the groundwater recharge and groundwater table simulations will be taken into account in the risk assessment.
The outcomes of the project will serve concerned authorities and those responsible for operational management in setting priorities for an integrated sustainable management and a reduced risk for groundwater resources in Belgium. Moreover such an approach is essential in meeting the requirements of the EU Water Framework Directive (WFD) towards EU member states to describe and monitor their groundwater resources.
Next to natural meteorological variations also human induced factors play a role. In the Belgian context the main influencing factors, determining the inflow and potentially resulting in a recharge deficit and an overall deterioration of groundwater resources are: climate, land-use/land cover (LULC) and groundwater demand for human activities. The combined effect of these factors makes that some groundwater bodies are under pressure. In these groundwater bodies the outflow exceeds the inflow generating a reduction in storage and hence an unsustainable situation.
A thorough knowledge of all three influencing factors and their interaction or combined effect is essential for a reliable estimate of the groundwater budget and a sustainable management. Especially because expected changes in climate, land-use and demand are likely to even reinforce these negative effects, having substantial socio-economic and environmental impacts. Hence there is a need for an improved understanding of climate-related and human-induced effects of groundwater drought. This should form the basis for an integrated approach which allows tackling these negative effects and safeguarding sustainability of groundwater resources.
The overall objectives of this project are:
- Increasing policy-relevant understanding of influencing factors (climate-LULC-demand) determining,groundwater drought.
- Obtaining reliable spatially distributed timeseries for groundwater recharge and water table levels, enabling to describe where (space) and when (time) groundwater drought occurred/occurs.
- Assessing the socio-economic and environmental impacts of groundwater drought at a large catchment scale for the present and future situation (coming 30 years).
- Mapping the individual and combined vulnerability of groundwater resources.
- Assessing the risk as a monetary loss in order to enable objective evaluation and reduce the groundwater drought risk towards the future.
- Developing a methodology and supporting quantitative tools aimed at planning and decision support with respect to (ground)water management, applicable at the level of river basins in Belgium and beyond.
- Informing the public, consisting of domain specialists and lay persons about the results of the analysis carried out in the case region, by means of an Internet-based indicator atlas.
In this project a combined water balance and groundwater modelling strategy is applied to obtain a reliable spatially distributed recharge and water table timeseries. The study area is the Dijle and Demer catchment in central Belgium, which correspond more or less with the underlying vulnerable Brulandtkrijt groundwater system.
The first step is a groundwater drought hazard assessment to increase knowledge and understanding of groundwater drought in a Belgian context. Starting point is a thorough analysis of the main influencing factors. Regarding the climate factor, a hydro-meteorological time-series analysis combined with a drought index approach enables the identification and characterization of historical and recent drought hazards. Land-use/land-cover characterization focuses on the estimation and mapping of agricultural land use change and change of impervious fraction cover, which are very sensitive and determining parameters for recharge estimation.
Once the spatially distributed recharge and water table timeseries is obtained the baseline scenario, which represent a sustainable groundwater system, is defined. Using the threshold method the “rules” to maintain the groundwater system sustainable are set. This baseline scenario forms the basis for the final groundwater drought risk assessment.
Based on groundwater simulations the baseline (reference) and current status of agriculture (crop yield), natural ecosystems and water supply are determined. A next step is to study the impact of changing influencing factors on the total system. Readily available socio-economic and climate scenarios (SRES from IPCC) for the future are combined with specific demand scenarios and used in a land-use change model. Using the water balance and groundwater model the individual and overall impact can be assessed, not only on groundwater resources, but also on future agricultural production, natural ecosystem health and water supply. This impact analysis forms the basis for vulnerability mapping for each of the separate aspects.
Finally the baseline scenario (sustainable system) and the defined threshold functions (“rules”) are used in combination with the scenario simulations to determine the separate risk for relevant socio-economic activities (agriculture, industry, etc.) and to represent this risk as a monetary loss. Also a combined risk is calculated using a multi-criteria approach. A loss of ecological values is considered as a limiting factor in the monetary risk calculation. Uncertainty of the influencing factors on the groundwater recharge and groundwater table simulations will be taken into account in the risk assessment.
The outcomes of the project will serve concerned authorities and those responsible for operational management in setting priorities for an integrated sustainable management and a reduced risk for groundwater resources in Belgium. Moreover such an approach is essential in meeting the requirements of the EU Water Framework Directive (WFD) towards EU member states to describe and monitor their groundwater resources.
