Supporting Danish river basin management plans
Ensuring good ecological status in estuarine and coastal areas through mechanistic modelling
Development of the second generation river basin management plans
In Denmark, the Danish Ministry of Environment’s Nature Agency is responsible for implementing the WFD and preparing plans for management and protection of Danish water bodies.
Percentage of summer chlorophyll-a concentrations explained by Danish nitrogen loading. © DHI
Under the WFD, it is compulsory for Member States to draw up RBMPs to safeguard each river district. Denmark’s first generation RBMPs were exposed to extensive criticism – particularly because the applied tools were considered unsatisfactory and implied considerable uncertainties in the defined targets on nutrient loading. In preparation of the second generation of RBMPs, improvements of the applied methods were therefore heavily called for. Along with the Danish Centre for Environment and Energy (DCE), we were commissioned to improve the tools for the second generation RBMPs with a focus on nutrient loading to support good ecological status in the marine water bodies.
Defining RBMPs is a difficult task. The directive is clear: Get all European waters into good ecological status. However, overdoing the effort may have considerable negative economic impact for agriculture – and hence Danish export. The development of strong and scientifically consolidated tools to assess and optimise the RBMPs are therefore highly appreciated by the non-governmental organisations (NGOs), agricultural associations and authorities.
Nitrogen reduction based on mechanistic models
The major objectives of the second generation plans are to set differentiated goals for the water bodies and to account for nutrient loading crossing borders between water bodies and between countries. Our solution was to develop marine modelling tools based on mechanistic regional and local models using MIKE Powered by DHI’s 3D modelling software MIKE 3 and ECO Lab. These mechanistic models describe the causal link between the physical parameters (for example, wind, currents and mixing), chemical parameters (such as nutrients) and the growth and biomass of the biological elements (such as phytoplankton and benthic flora), which are crucial to the overall health of the ecosystem.
Schematic example of a screening tool based on Danish N-loading developed for the authorities as part of the project. © DHI
Meteorological data and information on nutrient input from Denmark – as well as from our neighbours around the Baltic Sea – were entered into the mechanistic models. The modelling results were used to develop specific relationships between the nutrient loading from Denmark and the environmental status of each Danish water body. These relations were then applied to identify requirements for nutrient reductions in order to obtain good ecological status. Our solution provided the Danish water authorities with an improved tool for setting differentiated and optimised estimates of Danish nitrogen target loads for each specific water body.
Customised modelling and screening tool development
The WFD requires that Member States consult the public and stakeholders to identify factors to be included in the RBMPs. Prior to the project, Danish stakeholders had developed a set of ecological factors that needed to be included in the models. Hence, we used ECO Lab – our ecological modelling tool – to develop and adjust templates to meet their exact demand.
Precise basis for water management planning
Our solution supported the preparation, completion and submission of Denmark’s second generation RBMPs – plans estimated to have a direct cost of 200 million euros when fully implemented. Through the development of tools based on mechanistic models, uncertainties related to the estimated requirements for nutrient load reductions have decreased – providing a more precise basis for management planning.
The Danish water authorities now have a strong mechanistic modelling tool which can help assess impacts on the marine ecological status of a number of natural and anthropogenic pressures, such as climate change, fisheries, raw material extraction and dredging. This tool also helps to support decision making on the most optimal measures to invest in.
With the help of our advanced technologies and dedicated consultancy, our work in this prominent project has established us as an important player in Denmark when it comes to determining environmental status and assessing impacts from pressures such as nutrient loading. Additionally, the developed modelling approach can be exported to support consultancy services on ecological water management worldwide.
The Nature Agency is an organisation under the Danish Ministry of Environment, consisting of 23 nature management units across Denmark. The organisation implements the government’s policies regarding nature and the environment while aiming to secure clean water, protect nature, plan activities and provide information to the public about nature, forestry as well as land and wildlife management.
