Exploring Anglian Water’s water resource extremes using novel techniques

Climate change projections show UK rainfall patterns are expected to shift, placing extra challenges on regional water companies seeking security of supply for their customers.

One of the regions that could potentially be most affected is East Anglia, where much of the region’s water supply is provided by Anglian Water.

Lincolnshire chalk stream

With just under 630mm of rainfall annually, East Anglia is the driest region in the UK. Remarkably East Anglia is renowned for its diversity of wetland features and landscapes, including the Fens, the Broads and chalk streams, such as this example in Lincolnshire. Picture: Anglian Water

Geoff Darch is Water Resources Strategy Manager for Anglian Water. He said: “Our region is in a unique situation as the majority of water supplies come from significant aquifers and reservoirs that are slow to recharge. As such, the region is particularly vulnerable to droughts arising from multi-month to multi-year rainfall accumulation deficits.

“A few months of below average rainfall is manageable, but below average rainfall spanning one to two years can lead to significant drawdown of stored water.

“To ensure water resource risk is appropriately quantified, there is a requirement for these drought characteristics to be represented in the data used for our planning. This is where Anglian Water and the Met Office have been working together to explore novel approaches and datasets.”

UK annual average rainfall 1991-2020

UK annual average rainfall 1991-2020

The Industry Consultancy team at the Met Office has been supporting Anglian Water in key components of its Water Resource Management Plan (WRMP), further strengthening understanding of drought risk. Quantifying drought extremes – both today and in a future, warmer world – allows Anglian Water to enhance resilience.  It also supports key aspects of Anglian Water’s Drought Plan.

Dr Joe Osborne is a senior climate consultant at the Met Office. He said: “As part of this work, the Industry Consultancy team has developed a statistical model to enhance Anglian Water’s understanding of extreme events. The model is used to generate 1,000 alternative realisations of a 105-year historical period (1914-2018), with outputs on a 5-km grid over the region. The output validates rainfall and drought behaviour well.

“These simulations can be thought of as alternative historical outcomes allowing Anglian Water to test different and more extreme drought events. The work has also been extended to incorporate the effect of climate change, using climate model data from the UKCP18 climate projection dataset to allow for simulation of future rainfall at a number of key global mean warming levels.”

The Met Office has explored other emerging science on behalf of Anglian Water. For example, by exploring multi-year drought over the Anglian Water region.

Geoff added: “This activity helps us to deliver our stated purpose: to bring environmental and social prosperity to the region through our commitment to ‘Love Every Drop’. Understanding the investment decisions that are required to protect our customers against future weather and climate extremes is paramount.

“We need to make decisions based on robust and defendable science, and this requires us to ensure the robustness of our current assets and future systems to a wide range of potential droughts and climate scenarios. Undertaking this challenging work with the Met Office means that data-driven investments are made where appropriate, ensuring that we better protect our customers and the environment we serve in the face of an ever-changing climate.”

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