WATER

The water resource system model simulates (i) present and future needs for water, by homes, industry and farmers (ii) the system of water withdrawals (from rivers and groundwater), reservoirs, water transfers, treatment works (including desalination and waste water reuse), and water discharges back into rivers. The quantity of water that is available in rivers is estimated from historical records and future climate simulations. The model is a ‘simulation’ model, meaning that it simulates the movement of water around the system and can be used to estimate how frequently water shortages might occur in future. The model is used to test what infrastructure investments (e.g. to reduce leakage or build new reservoirs) and policies (e.g. to reduce demand) may be needed in order to ensure resilient water supplies.

Future climate simulations are provided by the Weather@Home climate modelling work and we use the DECIPHeR model to transform rainfall into runoff – and thus provide us with the flow inputs we require. The water supply system model framework was developed in close collaboration with water utilities. Because it is a national scale model, NISMOD cannot represent every detail of Britain’s water supply system, but it has been verified to be a reasonable approximation.

By simulating Britain’s water resource system we can answer a range of important questions. Which cities are likely to face shortfalls in supply? How far do the impacts of specific assets spread throughout the system (e.g. can expanding a reservoir in Wales increase supply reliability in London?)? How resilient is our water supply to changes in climate and demand? What are the benefits of national scale infrastructure projects that cross the boundaries of existing water companies and regions?