Thames Water has been allowed to progress a major water resilience scheme to its next development stage, but Ofwat has required further work on the project’s environmental, technical, economic, and strategic case.
The Lower Thames to West London Reservoirs Strategic Resource Option is designed to move water from a new abstraction point on the lower River Thames to the Queen Mary Reservoir, supporting water supply resilience in London and the Thames Valley.
Ofwat has issued a draft decision allowing the project to continue through the Regulators’ Alliance for Progressing Infrastructure Development, known as RAPID, gated process. The process is used to assess strategic water resource schemes as they move towards potential planning and delivery.
The decision does not amount to final approval. Thames Water must address eight priority actions before the next stage, covering environmental impacts, alternative options, costs, and the strategic justification for the scheme.
The project sits within a wider group of strategic water resource options being developed across the sector, including reservoirs, transfers, recycling, and desalination. These schemes are intended to help companies manage population growth, drought risk, environmental pressure, and long-term supply resilience.
Thames Water’s own strategic resource information describes RAPID as a joint team made up of Ofwat, the Environment Agency, and the Drinking Water Inspectorate. The company says RAPID is overseeing more than a dozen projects across several water companies to identify regional solutions that could be started in the 2025 to 2030 period.
The Lower Thames to West London Reservoirs scheme was brought forward after concerns over drought resilience and abstraction constraints. Thames Water has said that during the 2022 drought it experienced constraints on abstraction, implying that less water may be available during future droughts than previously anticipated.
The regulatory decision comes during a period of acute scrutiny for Thames Water. The company’s financial position, environmental record, infrastructure performance, and future ownership have all been under pressure, while the wider sector faces rising expectations for investment, transparency, and customer protection.
Water infrastructure has become a growth issue as well as an environmental one. A recent water capacity breakthrough unlocked almost 19,000 stalled homes, showing how utility constraints can affect planning, development, and local economic activity.
The Thames Water scheme points to a broader challenge: companies must invest in long-lived infrastructure while proving that proposed solutions are environmentally justified, affordable for customers, and robust against future climate and demand scenarios. Reservoir links and transfers can improve resilience, but they also raise questions about river flows, abstraction, ecosystem impact, land use, cost escalation, and regional water planning.
Ofwat’s insistence on further work reflects a more cautious regulatory environment. Water companies are no longer being judged solely on whether they propose large infrastructure projects. Regulators want evidence that options have been tested properly, alternatives considered, costs controlled, and environmental impacts understood.
That scrutiny has intensified as the sector’s investment programme expands. Customers are being asked to fund major upgrades through bills, while pollution performance, executive pay, leakage, and dividends remain politically sensitive. Large schemes have to demonstrate not only engineering ambition, but also necessity, affordability, and a credible link to long-term resilience.
Thames Water’s position makes the test sharper. A financially stressed utility must persuade regulators that it can plan and deliver critical infrastructure while managing cost, performance, and environmental obligations. The company also operates in a densely populated and economically significant region, where supply resilience is tied to housing, business activity, public services, and climate adaptation.
The RAPID process is designed to reduce the risk of weak projects advancing too far before major issues are resolved. By requiring priority actions at this stage, Ofwat is keeping the scheme alive while signalling that progression is conditional. That approach gives Thames Water room to develop the case, but it also prevents a green light from being mistaken for endorsement of the current proposal.
The wider industry will watch how the conditions are handled. Strategic water resource schemes are likely to become more prominent as climate change alters rainfall patterns and as environmental limits constrain abstraction. Companies will need to assemble technical evidence, environmental assessments, customer affordability arguments, and procurement plans well before construction decisions are made.
The decision also reinforces the role of regulators in shaping infrastructure pipelines. In energy, transport, telecoms, and water, long-term resilience projects increasingly sit within formal gate processes, value-for-money tests, and environmental scrutiny. Capital spending alone is not enough; companies must show why a project is needed, how it compares with alternatives, and how risks will be managed.
Thames Water’s next stage will test the strength of its evidence as much as its engineering plans. The scheme remains in development, but its path to approval now depends on whether the company can answer Ofwat’s concerns with a clearer and more robust case.
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