Within the framework of the Dutch Delta programme a long term water management plan is prepared to cope with the effects of climate change and socio-economic developments on flood risk management and fresh water supply in the Netherlands. The Delta model has been developed as a tool to support the policy analysis within the framework of the Delta programme. The Delta model combines a range of models to address issues related to flood risk management and fresh water supply. All models have been integrated in the Delta model - using the Delft-FEWS framework - to enhance the consistency in computations for the Delta programme.
Several of the models included in the Delta model existed already. These models were calibrated and validated in earlier stages, and are applied within other projects as well. Although these models were not developed specifically for the national policy analysis in the framework of the Delta programme, they were selected to allow for acceptance and support among the scientific community and the water managers.
In addition, several (regional) models have been extended to other parts of the country to allow for a consistent approach throughout the Netherlands. The acceptance of the models and the consistency of the approach was crucial for the successful implementation of the results of the Delta programme.
The Delta model has been used extensively within the framework of the Delta programme. The temporal and spatial resolution of some of the models appeared to be higher than technically necessary for policy analysis. In future new methods might be developed to reduce the resolution of these models for policy analysis without losing the acceptance of the water managers.
Key words: Delta programme, Delta model, integrated model, policy analysis, flood risk management, fresh water supply, Delft-FEWS, acceptance, consistency, resolution.
Several papers and articles describe the background of the Delta Programme and Delta model, so we will only give an overview here.
When the development of the Delta model started, a lot of different models were available. These models appeared to be not consistent in terms of scope, geographical distribution etc. For the Delta programme it was required to develop a consistent set of models (figure will be included to illustrate this). We will elaborate in this paper how we enhanced the consistency of the models in the Delta model.
The Delta programme also required the models to be accepted by the scientific community and (regional) water managers. During the development of the Delta model we learned that a lot of different stakeholders were involved, and they all had different perspectives (figure will be included to illustrate this). We will elaborate in this paper how we dealt with all different perspectives during the development of the Delta model.
Flood risk management
In flood risk management a lot of detailed models are being used in the Netherlands. The scope of these models is described in Slomp et al, 2014. We will include an overview of all models related to flood risk management in the paper, including a table and workflow indicating the relations between the models.
A dilemma during the development of the Delta model was that -- especially for flood risk management -- the results from the policy analysis had to be consistent with the results of previous studies. As the previous studies focussed on water management, the spatial resolution of these models was very high. For policy analysis less spatial resolution was required, and more (scenario) calculations. We will discuss how we handled this.
Another dilemma was that most models were used only for parts of the Netherlands. To prepare a consistency throughout the entire country we selected one approach for flood risk management in the Delta model and implemented this for all regions.
Fresh water supply
For fresh water supply a nation-wide hydrological model is available in the Netherlands (De Lange et al 2013). In the Delta model, this hydrological model is coupled to a number of impact assessment models. The scope of these models is described in Prinsen et al, 2014. We will include an overview of all models related to flood risk management in the paper, including a table and workflow indicating the relations between the models.
The main dilemma in the implementation for fresh water supply was the use of detailed models for acceptance and implementation of regional measures vs. use of aggregated and summarized results in policy analysis.
Implementation of the Delta model in Delft-FEWS
The Delta model has been implemented as an application of Delft FEWS (Werner et al, 2012). All details are (going to be) described in Verseveld et al, 2015, so we will focus in this paper only on the highlights.
As Delft-FEWS is a tool developed for forecasting, the robustness of the system is valued higher than the flexibility. We will describe in the paper how we allowed for the flexibility required for policy analysis, whilst maintaining the robustness of the system.
Discussion and recommendations
We will elaborate in this section on the issue of consistency, acceptance and flexibility.
The main conclusion is that the development of Delta model was successful, not only as it resulted in a tool that is being used, but also as it supported the process within the Netherlands to achieve commitment on the measures to be taken to cope with climate change and socio economic developments.
DGRW, RWS, IAC, Staf-DC, STOWA Will be added later