Southern Water sewers sealed across Andover Pan Parishes

This forms part of the £1.5bn Clean Rivers and Seas Plan, preventing more than 700 storm overflow releases in the last 12 months.

In the next five years, £341m will be invested in reducing overflow from almost 100 storm overflows in Hampshire and the Isle of Wight.

Southern Water carrying out work on a sewer sealing programme in Penton Mewsey and Appleshaw. (Image: Southern Water)

To address the rising public concern over storm overflows, more than £70m has already been spent on sustainable solutions, infrastructure upgrades and cutting-edge AI.

A Southern Water spokesperson said: "These early results show the plan beginning to make a difference even as the scale of the challenge remains significant.

"Storm overflows remain a major issue nationally, and Southern Water acknowledges that sustained, long‑term action is needed to deliver the step‑change customers and communities expect."

Southern Water said a key part of tackling storm overflows is understanding why they happen.

In many areas, rainwater from roofs, roads and hard surfaces still flow into the same pipes that carry wastewater.

In others, particularly in chalk landscapes, rising groundwater enters the sewer system during wet months.

When these flows overwhelm the network, storm overflows act as a safety valve to prevent flooding in homes, schools and streets. 

The spokesperson added: "This doesn’t make storm overflows acceptable, but it does show that the root challenge is managing and stopping rainwater and groundwater entering our sewers.

"Without addressing this, we cannot reduce storm overflows in a lasting way."