Written submission from Affinity Water (DCU0083)

Affinity Water – Data Centres Position

Introduction

Affinity Water is the UK’s largest water‑only company, supplying drinking water to approximately 3.9 million people across London, the South East and the East of England. Our supply area includes the Slough–West London corridor, which hosts the UK’s highest concentration of data centres.

The rapid expansion of data centre and Artificial Intelligence (AI) infrastructure raises important questions for water security, environmental protection and infrastructure planning, particularly in regions already classified by the Environment Agency as severely water stressed.

This document sets out Affinity Water’s perspective on how data centre growth interacts with statutory water planning frameworks, why current systems are under strain and what changes are required to ensure growth can be delivered sustainably.

Summary of Affinity Water’s position

• Affinity Water does not oppose the expansion of AI and data centre infrastructure but considers that development must be governed by clear environmental and water resource constraints.
• Water availability must be treated as a fundamental consideration in decisions about the location, scale and timing of data centre development.
• The current planning system does not provide sufficient early visibility of data centre proposals or their water requirements.
• Water Resource Management Plans (WRMPs) are not designed to absorb rapid, clustered non‑household demand in water‑stressed regions.
• Without reform to planning guidance, disclosure requirements and integration with water resource planning, data centre growth risks undermining water resilience and environmental objectives.

Data centres and water security

The Government’s growth agenda and commitment to utilise AI to improve efficiency in the public sector will drive further expansion of AI infrastructure, including data centres. In September 2024, the Secretary of State for Science, Innovation and Technology designated data centres as critical national infrastructure alongside energy and water systems. Culham in Oxfordshire, only seven miles from the proposed location of the White Horse Reservoir, has been designated as the country’s first AI growth zone. The Chancellor has also emphasised that the Government would not hesitate to review planning applications where there was a potential gain for regional and national economies.

The majority of the UK’s 500 existing data centres are based in the South East of England – an area identified by the Environment Agency as being severely water stressed. Data centre demand for water for cooling purposes is variable, ranging from a few cubic metres up to potentially 10 million litres per day depending on size and recycling infrastructure. Whilst power can also be used for cooling purposes, water is often regarded as a cheaper option and is therefore preferred.

The rapid expansion of AI infrastructure has not been adequately accounted for in water resource and infrastructure planning at either a regional or company level and the current planning system provides little visibility of where developments are proposed. Current projections do not fully account for emerging sources of demand, including data centres, housing and other growth sectors that government policy is actively seeking to expand, as pressures across these sectors have increased only recently and future demand remains uncertain.

Affinity Water supplies the Slough–West London corridor, which hosts the UK's highest concentration of data centres. Within Affinity's region approximately 125 data centres are either proposed or under construction, with some individual facilities requesting supplies of up to 35 litres per second, equivalent to the peak water demand of 3,500 homes. One proposal sought to consume 21ML/day, equivalent to the water needs of approximately 147,000 people. The planning framework is built around household growth and per‑capita consumption and has not adapted to commercial users whose water needs can match those of a market town.

Why the current system is not working

      Planning visibility and classification

Data centres are not easily identified through the planning process. At present, they are commonly categorised within general industrial or commercial use classes, which limits early visibility of developments with exceptionally high-water demand. This constrains the ability of water companies and regulators to engage early on water availability, infrastructure requirements and environmental impacts.

As a result, data centre proposals can quickly consume resource headroom, which is a particular concern in water‑stressed areas such as the South East. The outcome is a growing gap between available supply, environmental restrictions and actual demand.

      Interaction with Water Resource Management Plans

Water demand from data centres is not currently accounted for in WRMP24 forecast calculations, despite estimates that the UK data centre industry already consumes significant volumes of water annually, with projections suggesting this could increase substantially by 2050 depending on industry growth and the future energy mix of the country.

WRMPs are designed to manage long‑term household growth and uncertainty. They are not designed to absorb rapid, concentrated increases in non‑household demand arising late in the planning cycle, particularly in water‑stressed regions.

Evidence from Affinity Water’s WRMP

Our WRMP24 includes Target Headroom to manage risks that may materialise over the planning period (2025–2075), including outage, maintenance, water quality deterioration and other sources of uncertainty. This volume is calculated in line with Environment Agency guidance and is c.69Ml/d for our Central region and c.77Ml/d for the total company, equivalent to approximately 10% of our total annual average Deployable Output (DO).

The volume that could theoretically be made available for consumption by data centres has been apportioned by water resource zone based on the Water Available for Use (WAFU) in a given year within AMP8 (2025–2030). WAFU is derived by combining surplus water and Target Headroom and applying a factor of 0.1. This approach allocates up to 10% of available water within a resource zone to data centre demand while maintaining a healthy Target Headroom allowance.

Table 1: Water potentially available to meet demand from data centres within AMP8

Supply to a data centre for cooling purposes is only considered viable from a WRMP perspective where the cumulative volume required, including other approved data centres in the same water resource zone, does not exceed the available volume. This is applied as a pass/fail screening metric at an initial stage. Further criteria must also be met, including the location of the data centre and any network upgrades required.

Target Headroom included in WRMP24 is intended to protect system resilience rather than to support structural growth. Where data centre demand draws on this headroom, the margin available to manage drought risk, asset failure or water quality deterioration is reduced.

Key issues for policy and planning

To ensure that the expansion of data centres is environmentally sustainable and compatible with water security objectives, the following actions are required:

• Planning policy must provide early visibility of data centre proposals and their water requirements, including clear identification within the planning system.
• Government should issue guidance on acceptable levels of potable water supply to data centres, particularly in water‑stressed regions.
• Mandatory requirements for water reuse, recycling, demand forecasting and minimum efficiency standards should be applied to data centre developments.
• Water resource planning frameworks should be adapted to reflect rapid, clustered non‑household demand arising outside traditional household growth assumptions.
• Financial contributions toward water infrastructure should be considered where necessary to support regional and local water supply resilience.