The trial period, which starts on 12 January and runs for five years, will see the company release water from its Grimworth reservoir to help improve the ecology in the River Dibb, in north Yorkshire.
The flow through that river is inconsistent, preventing native wildlife from establishing itself and thriving in the area.
The Water Framework Directive states that at least 32 per cent of water bodies will be required to reach ‘good’ classification by 2015, and for all water bodies to achieve this status by 2027.
Yorkshire Water said it will be monitoring the river to understand the impact the trial has.
Yorkshire Water’s environmental assessment team leader Mark Tinsdeall said: “This project will benefit an important river that hasn’t had a reliable flow since the reservoir was first constructed 150 years ago, resulting in it regularly running dry.
“This project is great news for wildlife in the area, giving it a real chance to flourish.”
The scheme is part of a wider programme of work being conducted by Yorkshire Water to improve more than 100km of rivers over the next five years.