Wales’ largest water company Dŵr Cymru Welsh Water said it made “good progress” on improving its services in the 2023/24 financial year.
Just 107 pollution incidents were logged in the year, it said, adding this was 'only 20% higher' than the previous year.
Ofwat classifies a ‘pollution incident’ as “a discharge or escape of a contaminant from a water company sewerage asset affecting the water environment”.
Annual leakage increased to 251.7 megalitres daily, up 4% year-on-year.
Ofwat described leakage as “the water that companies cannot account for; so water that has entered their system but has not been delivered to homes, businesses or used in their operations”.
One megalitre is equivalent to one million litres, meaning Welsh Water lost 91.87 billion litres of potable water in the year (compared to Thames Water’s estimated 228.3 billion litres).
A typical Olympic-sized swimming pool holds 2.5 million litres, meaning just 36,848 Olympic-sized swimming pools worth of water was lost in the leap year.
Internal sewer flooding incidents, classified by Ofwat as “flooding which enters a building or passes below a suspended floor”, increased 19% to 201.
“Looking to 2024/25, the company will continue to deliver on the promises set out in its Manifesto,” said Welsh Water.
The group spent £483m “to maintain and improve its assets in the last 12 months”.
“Our plans have to find the right balance of being financeable, deliverable and affordable for our customers without storing up problems for future generations. Whilst there's still much more to do, we are making good progress against the commitments we've made," said chair Alastair Lyons.
Tackling phosphorus
Welsh Water is implementing plans to reduce phosphorus in rivers via a 1.8-hectare wetland project that will serve as a “green filtering system for stormwater discharged from the nearby storm overflow during heavy rain”.
Chief executive Peter Perry said: "We're delighted to be creating this innovative wetland that will mitigate the effects of wastewater from a storm overflow by naturally removing the phosphorus.
“In line with Welsh Government policy, we are prioritising investment in the storm overflows that cause environmental harm rather than those which spill the most.”