London faces increased risk of water shortages in the future due to climate change and population growth if no actions are taken to increase supply or reduce demand, according to a new study from Oxford University’s Environmental Change Institute (ECI).

The research presents a new methodology for water managers to incorporate climate change uncertainties into water resources planning.

The study says that while water resources managers have significant experience in planning and operating their systems in the face of hydrological and weather variability, the reality of climate change, however, is posing new challenges.

Whilst the precise impacts of climate change for temperature, precipitation and water availability remain uncertain, water managers still need to take into account these uncertainties in their water plans. In the UK water companies are now legally obliged to evaluate the impacts of climate-related risks on their systems.

To help water managers address the challenge, the study has developed a methodology for incorporating climate change related uncertainties in water resources planning. The methodology uses a risk-based metric to compare different water management options on the basis of their ability to reduce risks of water shortages under continuously changing climate conditions.

The methodology responds to the need in the UK and worldwide for a way of identifying water management investments which are proportionate to the risks the water systems are facing. Supply-side and demand-side management strategies can be compared based on how cost-effective they are at reducing risks to acceptable levels.

The risk-based methodology was applied to the London water supply area to characterise the most important uncertainties and identify water management options that are capable of reducing the harmful impacts of climate change.

Results from the study demonstrate that without further supply or demand interventions, the combined effects of climate change and population growth are projected to increase the risk of water shortages in the future in London.

The research, led by Edoardo Borgomeo and Director of the ECI Professor of Climate and Environmental Risks Jim Hall, was carried out in partnership with Thames Water and the Environment Agency. The study contributes to the ongoing discussion in the UK water sector on whether the current approach to water resources planning should change for the next round of water resources management plans in 2019.

The risk-based methodology presented will be useful to decision makers because it provides a coherent approach for incorporating new information on climate uncertainty into the decision-making process to evaluate the risk of water shortages.

Traditional water planning focuses the water planner’s attention on setting supply-demand balance targets for the future, while the approach in the study shifts the focus onto observable outcomes of concern to water users and their probability of occurrence.

The study shows that probability concepts can help water planners identify which sources of uncertainties are likely to have the greatest impacts on long-term planning and the degree to which they will influence the probability of undesirable outcomes. The new methodology provides a route to transparently structure all the available evidence and compare between different water management actions in a way that is directly relevant to decision makers.

Click here to read the study in full.