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?



The distribution of drought year severity and probability for the historical (a), baseline (b), near future (c) and far future (d) periods. Bars represent the distribution of days of restriction during drought years for a given region – with the box covering the 25th-75th percentile, a vertical line at the median, whiskers extending to 1.5 times the interquartile range and ‘outliers’ indicated by circles. The position on the Y-axis represents the probability of there being a drought year for a given region. Bars are coloured to distinguish between different regions. Regions with three or fewer drought years in that period show points only.


National Infrastructure Commission

An early version of the NISMOD water supply model was used to provide the analysis for the National Infrastructure Commission’s analysis of water infrastructure: Preparing for a Drier Future.


National Framework for Water Resources

The Environment Agency’s National Framework for Water Resources used our model to test the resilience of water supplies in England and Wales.






Weather@home produces the national climate scenarios for water resource system simulation. Weather@home is a modelling framework that consists of a global and a regional climate model, driven with prescribed sea surface temperatures and sea ice projections. Weather@home was used to create ensembles of climate conditions for England and Wales that are large enough to facilitate investigation of drought extremes and their spatial dynamics.


DECIPHeR is a national hydrological model developed at the University of Bristol to enable drought risk analysis and water resource system simulation.



Assessing water resource system vulnerability to unprecedented hydrological drought using copulas to characterize drought duration and deficit

Global climate models suggest an increase in evapotranspiration, changing storm tracks, and moisture delivery in many parts of the world, which are likely to cause more prolonged and severe ... read more

Trading-off tolerable risk with climate change adaptation costs in water supply systems

Choosing secure water resource management plans inevitably requires trade‐offs between risks (for a variety of stakeholders), costs, and other impacts. We have previously argued that water ... read more

Resilience of water resource systems: lessons from the UK, Water Security

We explore the triumvirate of resilience – ‘persistence’, ‘adaptability’ and ‘transformability’ – in the context of England’s water supply infrastructure system. Risk-based decision-making and ... read more

Risk‐based water resources planning in practice: a blueprint for the water industry in England

Resilient water supplies in England need to be secured in the face of challenges of population growth, climate change and environmental sustainability. We propose a blueprint for water resources ... read more

Drought and climate change impacts on cooling water shortages and electricity prices in Great Britain

The risks of cooling water shortages to thermo-electric power plants are increasingly studied as an important climate risk to the energy sector. Whilst electricity transmission networks reduce ... read more

The spatial dynamics of droughts and water scarcity in England and Wales

Water scarcity occurs when water demand exceeds natural water availability over a range of spatial and temporal scales. Though meteorological and hydrological droughts have been analysed over ... read more

Navigating the water trilemma: a strategic assessment of long‐term national water resource management options for Great Britain

Potential increases in water demand, alongside uncertainties in water availability due to climate change, mean that Britain’s water supply system could become increasingly stressed over the ... read more

Risk, robustness and water resources planning under uncertainty

Risk‐based water resources planning is based on the premise that water managers should invest up to the point where the marginal benefit of risk reduction equals the marginal cost of achieving ... read more