Severn Trent said it will invest £565mln that will create 2,500 new jobs in the Midlands.
The utility firm will improve river quality by upgrading sewage treatment works, treating and reducing spills from storm overflows, and installing river quality monitoring, while boosting water supplies with systems to cut pollution.
It will also trial the creation of two bathing rivers, including reducing harm from storm overflows by reducing spills into the area during the bathing season as well as enhancing protection for homes from flooding, repairing customer supply pipes and installing smart water meters.
Meanwhile, Pennon has pledged £81mln of extra investment for South West Water to upgrade the Knapp Mill water treatment works and increase water supply resilience by supporting water transfers.
It will also trial ways to help customers save water, use nature-based solutions to avoid flooding and reducing harm from storm overflows.
Finally, United Utilities has allocated £63mln to improve the river environment by increasing sewer capacity, to develop nature-based solutions through partnership working and to investigate ways to reduce harm from storm overflows.
The move comes after regulator Ofwat invited English water companies to submit environmentally-friendly proposals in July 2020.
Pennon and United Utilities dipped 1% to 1,040p and 981.82p respectively, while Severn Trent was flat at 2,504p.