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What do we want to know?

The main contribution of this case study to MEDIATION is to develop and test an improved methodology for the identification of impact and adaptation thresholds, key risk factors and potential adaptive responses. The improvements focus on two important aspect: 1) impacts of and adaptation to the full distribution of climatic conditions (including (changes in) variability and extremes), 2) identification of and responding to adaptation thresholds.

In this case study MEDIATION aims to address the following research or policy question:

  • Are there salient adaptation thresholds in agriculture, nature and tourism sectors in the Rhine-Meuse Delta in the Netherlands triggered by climate change induced changes in the water system and/or proposed adaptation measures?
  • Does recognition of potential thresholds change the requirement for water policy?

 

What do we know?

The Rhine-Meuse Delta in the Netherlands is important as strategic freshwater reservoir, for river-discharge regulation (peak discharges of the Rhine-Meuse are diverted from the port and city of Rotterdam), for recreation, aquaculture (shellfish, lobster, etc.), nature (especially intertidal areas), and as gateway to the port of Antwerp (Wester Schelde). While the Deltawerken are still an international icon for Dutch water management, current land-use and water-management plans put emphasis on their environmental impacts (water quality), as well as their appropriateness under climate change. Currently, water management strategies and land-use plans are reconsidered in order to minimize flood risks, optimize freshwater availability, reduce salinisation, and improve water quality and biodiversity. This reorientation is explored in the National Water Plan (2008) and the Delta Program (2010).

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Illustration of the proposed case study. Source: Wageningen UR, IMARES (2010)


Some extra background

For long water impact assessments and adaptation studies have focussed on selecting the most cost effective measure to cope with a specific quantified stress. In the Netherlands, for example, water management is tailored to perform under a specific design discharge of 16,000 m³/s at Lobith where the River Rhine enters the Netherlands. Flood strategies (e.g. Ten Brinke and Bannink, 2004; Hoes, 2007) and drought strategies (e.g. Projectgroep Droogtestudie Nederland et al., 2005) are elaborated independently, each with their own water management interventions and scenarios. Modelling studies strongly focus on assessing conditions at the design discharge (e.g. Parmet et al., 2001; Silva, 2002; Schielen and Gijsbers, 2003; van Schijndel, 2005; te Linde et al., 2008) and models are often unsuitable for operating outside a narrow range of extreme conditions for which they were designed. The underlying structure of how diverse water and land-use systems interact with the full range of climatic conditions has been addressed rarely. In addition, the methodologies and models underlying impact assessments assume a smooth continuous relationship between climate stress and impact. More extreme outcomes of a changing climate and cases where key thresholds are exceeded (tipping points) are typically not considered.

Examples of (human induced) shifts and thresholds in socio-ecological systems in the region include: The Delta Works closed two estuaries, that subsequently turned into freshwater bodies: the Haringvliet and the Volkerak-Zoom lake. The seemingly unlimited fresh water availability created opportunities for the development of agriculture and drinking water supply, thereby boosting economic development. At the same time water quality of the new fresh water lakes deteriorated. Algal blooms and fish migration barriers especially are identified as a problem. The strategy is debated whether to restore estuarine dynamics (i.e. a saline gradient). Re-introduction of a saline-freshwater gradient may reduce the occurrence of algae blooms, but it also reduces freshwater availability for agriculture, drinking-water supplies and greenhouse horticulture in the region. The discussions on partially opening the estuaries and reintroducing a saline-freshwater gradient are linked to the debates on using the estuary for discharging future Rhine peak flows, whereby relieving the Rotterdam / Rijnmond area. The effect of peak flow discharge on the region’s socio-ecology is a new topic for debate.

References

Hoes, O. (2007). Aanpak wateroverlast in polders op basis van risicobeheer. Technische Universiteit Delft, Delft, NL.

te Linde, A. H., J. C. J. H. Aerts, R. T. W. L. Hurkmans and M. Eberle (2008). Comparing model performance of two rainfall-runoff models in the Rhine basin using different atmospheric forcing data sets. Hydrol. Earth Syst. Sci. 12 (3), 943-957.

Parmet, B. W. A. H., W. van de Langemheen and E. H. Chbab (2001). Analyse van de maatgevende afvoer van de rijn te lobith: onderzoek in het kader van het randvoorwaardenboek 2001. 2002.12. RIZA rapport. Ministerie van Verkeer en Waterstaat, Directoraat-Generaal Rijkswaterstaat (RWS), Arnhem, NL, 50.

Projectgroep Droogtestudie Nederland, RIZA, HKV, Arcadis, KIWA, Korbee en Hovelynck, D. Klopstra, R. Versteeg and T. Kroon (2005). Water shortages in the Netherlands: its nature, seriousness and scope (in Dutch). RIZA-rapport 2005.016; ISBN 9036957230. Ministerie van Verkeer en Waterstaat, Directoraat Generaal Water, Lelystad, NL, 120.

Schielen, R. M. J. and P. J. A. Gijsbers (2003). DSS-large rivers: developing a DSS under changing societal requirements Physics and Chemistry of the Earth, Parts A/B/C 28 (14-15), 635-645

van Schijndel, S. A. H. (2005). The Planning Kit, a decision making tool for the Rhine branches. In Floods, from Defense to Management (eds Alphen, J. v., E. v. Beek and M. Taal), pp. 763-769. Taylor & Francis Group, London.

Silva, W. (2002). How much (high)water can enter our country through the Rhine at Lobith, now and in the future. RIZA rapport 2003.015; ISBN 903695494. Institute for Inland Water Management and Waste Water Treatment (RIZA), Lelystad, NL, 44.

Ten Brinke, W. B. M. and B. A. Bannink (2004). Risico’s in bedijkte termen. RIVM rapport 500799002. RIVM, Bilthoven, NL.

 

 

 

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