Climate adaptation in Aa of Weerijs catchment: web application from EIFFEL project

Description

This web application is an outcome from one EIFFEL project  pilot, dealing with climate adaptation in the river catchment of Aa of Weerijs, focused on water shortages / droughts and soil carbon. The catchment is transboundary, with its upstream part located in Belgium (199 km2) and the downstream part, which is the focus of this pilot, located in the Netherlands (147 km2). As agriculture is man activity in the area, the water shortages and  droughts that have occurred in recent years led to requirements for adaptation measures and strategies for increasing water retention and availability. Climate adaptation planning is led by two key stakeholders in the area: the Province of Noord Brabant (PNB) and the Water Board Brabantse Delta (WBD). The research undertaken within EIFFEL project contributed to such ongoing plans by developing adaptation strategies based on Nature Based Solutions (NBSs) that could be implemented in the Dutch part of the catchment. For design and development of these strategies, an integrated hydrological model has been set up using a combination of GEOSS and local data. In consultation with the main stakeholders, during several stakeholder workshops and meetings, Key Performance indicators (KPIs) were identified, related to water availability, which were then used to assess the effectiveness of the proposed adaptation strategies under scenarios of climate change. Several of these strategies were also tested for their effectiveness in soil organic carbon sequestration, using a dedicated soil carbon model that was coupled with the hydrological model. All results are provided in the associated web application. Brief summary of the key components is provided below:

Hydrological and soil carbon models

The Aa of Weerijs hydrological model has been set up using the MIKE SHE modelling system of DHI, Denmark. The model is with horizontal discretization of 500 x 500 m, and it is a fully integrated model that couples surface and sub-surface hydrology. It provides spatially distributed modelling outputs such as river discharges, groundwater levels, soil moisture, actual evapotranspiration, and others. These outputs have been used to calculate values of the KPIs for assessing the effectiveness of the adaptation strategies. The model has been calibrated and validated using measured data (river discharge, groundwater levels and actual evapotranspiration) from the period 2010-2019, which represents the current hydrological conditions in the catchment..

The soil carbon model (named CARBI), has been developed partly based on the Daisy plant production model, and uses inputs such as soil moisture and temperature, soil clay content, current soil organic carbon and vegetation (land use), to simulate modifications in soil organic carbon when alternative land use (resulting from NBS-based adaptation strategies) is implemented. The model is loosely coupled with the hydrological model which provides soil moisture output as input to CARBI, which in return provides modified soil organic carbon content as output to modify the soil hydraulic properties to the MIKE SHE hydrological model.

Climate change scenarios

Climate change scenarios for the Netherlands have been used for the analysis, as developed most recently (in 2023) by the Royal Dutch Meteorological Institute - KNMI. Two scenarios of greenhouse gasses emissions have been considered: 'H' (High - increase at the same rate until 2080 and then levelling off, resulting in global warming of 4.9°C by year 2100, compared to pre-industrial era) and 'L' (Low - in line with the Paris Agreement to limit global warming to well below 2°C, resulting in global warming of 1.7°C by year 2100). These emission-related scenarios are then combined with two scenarios of 'wetness': 'wet' scenario (denoted by 'N', from 'nat' in Dutch), in which the winters are much wetter and the summers slightly drier, and 'dry' scenario (denoted by 'D'), in which the winters are slightly wetter and the summers much drier. These combinations lead to the four climate change scenarios: 'HN', 'HD', 'LN' and 'LD', considered in the analysis of the Aa of Weerijs catchment, by taking the near future into account, namely the decade 2050-2059.

Key performance indicators

In consultation with the main stakeholders, the following KPIs have been identified for assessing the performance of the adaptation strategies:

• Surface water availability
• Groundwater availability
• Soil moisture index
• Groundwater dynamics parameters
• Localized model outputs (river discharges and groundwater levels)
• Soil organic carbon difference

The values of these KPIs have been calculated for specific locations within the catchment, or for the whole domain, depending on the type of KPI. Initially these have been calculated for comparing their values under current conditions and the four climate change scenarios.

Nature based solutions for climate adaptation

Based on investigations in previous projects, the following NBSs have been considered:

• Ditch blocking
• Wetlands restoration
• Infiltration ponds
• Heathlands restoration
• Tree planting
• Brook bed barriers

Initially, single-measure adaptation strategies have been simulated for each of these NBSs, using spatial distribution from previously developed 'opportunity maps'.

Adaptation strategies

Two drought-related adaptation strategies have been designed consisting of mixture of NBSs, by selecting best performing NBS at given location with respect to groundwater availability (considered to be most important KPI by the stakeholders). The overall spatial coverage of these strategies was based on existing plans for nature development in the area. The performance of these strategies was assessed by comparing HD climate change scenario with and without adaptation strategies.

Modification of soil organic carbon was tested for single measure strategies with land use change, namely wetlands restoration, heathlands restoration and tree planting. One additional strategy of extreme reforestation in the whole catchment was also tested.

All results in terms of the KPIs are available in the associated web application. 

Further data used for setting up the hydrological and soil carbon models are also provided under the 'Models and data' section in the same web application.  

Knowledge Resources

Related links

Additional details