Delta Scenarios

All the Preferential Strategies and measures are directed by the Delta Scenarios: plausible views of future climate and socio-economic trends, looking ahead to 2050 and 2100.

The Delta Scenarios work with a range of perspectives that could all actually become a reality. This provides a clear picture of the bandwidth in climate change and other developments. Working with a bandwidth for climate change fits with the insights of the IPCC (Intergovernmental Panel on Climate Change).

The first set of Delta Scenarios was drawn up in 2012. The hydrological conditions were based on the KNMI’06 scenarios of the Royal Netherlands Meteorological Institute, yet anticipate the insights into climate trends published by the IPCC in 2014. The Welvaart en Leefomgeving (Prosperity and the Living Environment, WLO) study conducted in 2006 was used as the point of departure for the potential impact of socio-economic trends on the use of land, water, and space up to 2050. These WLO scenarios have been drawn up by the Netherlands Bureau for Economic Policy Analysis (CPB) and the Netherlands Environmental Assessment Agency (PBL).

In 2015, CPB and PBL updated the 2006 socio-economic scenarios. In December 2015, global agreements were set down in Paris regarding the reduction of global warming to a maximum of 2 degrees Celsius by 2100. The Delta Programme has commissioned Deltares, KNMI, PBL, and CPB to explore the consequences of these agreements for the Delta Programme. Their conclusion was that these new insights still fall within the bandwidth of the Delta Scenarios, and that the impact of the Paris agreements will not be manifest in the water taskings until 2050 at the earliest. Ergo, the Preferential Strategies currently still constitute the proper basis, but incorporation of these new insights into the Delta Scenarios would be advisable when it comes to the selection of the next batch of measures set out in the adaptation tracks, particularly those relating to the freshwater supply.

In 2017-2018, these new insights into socio-economic trends and the Paris climate agreements were incorporated into an interim update of the Delta Scenarios.

The update is based on adjusted expectations regarding the future use of land (larger differences between emerging and depopulating regions), on a more realistic distinction between autonomous developments in sectors (e.g., with respect to the increase in irrigated surface area), and on intended policy (e.g., regarding flushing to combat salinisation). Furthermore, another version has been added to the scenarios: PRESSURE-PARIS, reflecting how a reduction in CO2 emissions can affect the water taskings (for example, with respect to reducing soil subsidence in peat grassland areas). The Delta Plan on Freshwater Supply is using this interim update to update its bottleneck analysis and determine the next step in the adaptation strategies. It can also serve as input for the stress tests being conducted under the Delta Plan on Spatial Adaptation.

Meanwhile, there is growing evidence that with effect from the middle of this century, the sea level may rise faster than has been assumed in the Delta Scenarios. The IPCC is expected to publish a new report in September 2019. The Minister of Infrastructure and Water Management will inform the House of Representatives on this report. The next KNMI climate scenarios are scheduled to be completed by 2023; the Delta Scenarios will be updated accordingly.

General description of the scenarios

The scenarios provide qualitative and quantitative data on the climate, water systems, water consumption, and the use of land. The qualitative information consists of narratives and maps that describe the backgrounds and demonstrate the interconnectivity of the issues. The quantitative data is reflected in the form of indicators, such as those presented in the overview table in the abridged version of the Delta Scenarios. They cover time series for various factors, including temperature, precipitation, and river discharges as well as geographic databases pertaining to the use of space, soil subsidence, and salinisation in the Netherlands. The databases are specifically intended to be used in the quantitative model instruments for long-term policy choices (National Water Model) and the National Hydrology Tools (NHI).