The Friends of the Ems (FOTE) campaigns to improve flow in the river, which also supports threatened wildlife.
Formed in August last year, the group is now welcoming the planned review of Portsmouth Water’s pumping licence.
This licence governs the process of abstraction: how much the company can remove from the river’s underground sources.
It also governs how much it should pump into the river at times of low flow, a process known as augmentation.
In a meeting with FOTE, the Environment Agency said it wants to review the licence to make it more sustainable.
A FOTE spokesman said that this was an ‘encouraging pledge’ from the agency: ‘We are still cautious and will wait and see what happens. But after only a year of campaigning for our beautiful river this is a major piece of good news.
‘Local people have joined us in our fight for the Ems, as have our councillors and MP, and it seems our voices are being heard.
‘It is still important to remember that while water flow is crucial – otherwise there would be no river – we also need improvements to the Ems as a wildlife habitat and to the quality of the water.’
In the meeting, Simon Moody, area director for the Environment Agency, said he would like to see better augmentation in place before next summer, when the river is at greatest risk.
An Environment Agency spokesman added: ‘We share the ambition for the River Ems to be a thriving, diverse ecosystem and are working with the local community, Portsmouth Water and other groups to achieve this.
‘By working with others we hope to see an improved and more effective scheme in place to support flows in the River Ems during the summer months when the river is at greatest risk.
‘Only by working in partnership can chalk streams be improved and preserved for future generations.’
In September last year, a failure of Portsmouth Water’s augmentation system left large sections of the river dry, with fish stranded and dying.
FOTE believes the current licence is totally inappropriate for the Ems, which has a variable flow.
In February, when the river is usually at its peak, there can be 700 times as much water flowing as in a typical September - but the company’s licence allows it to remove the same amount of water every day of the year.
A Portsmouth Water spokeswoman said: ‘After two years of study, carried out in conjunction with the Environment Agency and the Friends of the Ems, we are aware that an element of our abstraction from our nearby boreholes, where we feed water into the River Ems to augment the natural flow has not been as effective as originally intended when this arrangement was agreed and put in place in 2016.
‘We believe the reason for this relates to unexpected chalk formations under the bed of the river which are causing this additional water to drain downwards into the chalk aquifer.’
Portsmouth Water says it is looking at sustainability and to make changes, but has a primary legal responsibility to supply water.
The spokeswoman added: ‘We will be working with the Environment Agency to make the necessary changes to the river flow augmentation elements of these licenses.
‘This will ensure we protect the integrity of the River Ems to the very best of our ability and should result in a more consistent flow of water in the river.’