Three Valleys Water - Great Britain

In Great Britain, the Environment Agency (EA) asks the water companies to assess their longterm risks on available water resources in their capital programs.

The South-East of England is particularly affected by the growing urbanization of the Greater London area on the one hand and by the consequences of climate change on the other hand. Three Valleys Water, one of the Veolia Water's subsidiaries in the United Kingdom, operating the water services for the Northern and the Western suburbs of London, is therefore particularly concerned by this issue and had to produce a risk assessment for the 25-year Water Resource Plan asked by the EA.

The main objective of the analysis conducted at Three Valleys was to study the impact of climate change in the long-run on the two main aquifers, providing 70% of the raw water treated by the company.

To this end,Veolia Water specialists implemented new tools allowing the company to operate the results of the IPCC Global Climate Models (GCMs), to adapt them to the regional scale and to generate the forecasted impacts on the evolution of the groundwater resource in 25 years time. Technically, a climate series generator was used to study the daily temperatures and rainfall patterns. From a synthesis sequence, a hydraulic model for the aquifer was implemented to simulate the water balance and the water table level.

This work was conducted in association with the French Laboratory of Dynamic Meteorology, the Ecole Polytechnique and the French National Research Center for Scientific Research.

The results show a general drop of the groundwater levels, affected by climate change. But the most important thing is that the behaviour of the chalk aquifer is likely to change on an inter-annual basis, with more variability. The peaks of groundwater levels are likely to become more important and more frequent, with values outside the range already observed, especially in the lowest levels.