Project Tethys

Alex McKay

Partnering for River Restoration on Salisbury Plain

Wessex Rivers Trust will be working with Wiltshire Wildlife Trust and the Defence Infrastructure Organisation (DIO) of the Ministry of Defence on a project to revive river habitats across the upper Hampshire Avon river catchment. This partnership tackles the challenge of balancing sustainable water use associated with military activity, and the conservation of the Hampshire Avon’s unique chalk river ecosystem.

The first phase will involve a comprehensive River and Floodplain Rehabilitation Plan to identify restoration opportunities across both winterbourne and perennial river systems, with delivery to follow from 2027.

Addressing Groundwater Challenges
Salisbury Plain and its surrounding areas provide potable water for military garrisons, the Salisbury Plain Training Estate, and Dstl Porton Down—all of which depend on groundwater abstraction. Since 2003, regulatory changes have aimed to protect river systems from over-abstraction. However, unlicensed abstraction has continued to affect river flow and chalk stream habitats in the upper Hampshire Avon catchment, a designated Site of Special Scientific Interest (SSSI) and Special Area of Conservation (SAC). 

Discussions with the Environment Agency (EA) and Natural England (NE) in 2022 confirmed that groundwater use was impacting this globally rare habitat. A Habitats Regulations Assessment (HRA) outlined the need for action, prompting renewed efforts to sustainably manage water use while protecting this delicate ecosystem.

Enter Project Tethys
Project Tethys is designed to tackle these challenges head-on, blending research with hands-on river habitat conservation. Key elements include:

• Habitat restoration on the upper Avon, lower Wylye, Ebble, or River Frome (Dorset)
• Winterbourne habitat restoration on the upper Ebble, Nine Mile River, Allen, or Crane (Dorset)
• Targeted restoration inside and outside the River Avon SAC to support vulnerable species, including the Desmoulin’s whorl snail.

Why Collaboration Matters
Project Tethys brings together the Defence Infrastructure Organisation’s operational expertise, the Wiltshire Wildlife Trust’s conservation experience, and our own knowledge of river systems to create lasting benefits for both people and wildlife.

This initiative reflects a broader commitment to rethink how we manage water in stressed catchments like the Hampshire Avon. Restoring flow, habitat connectivity, and natural hydrology isn’t just about conservation; it’s about resilience. Healthy rivers buffer communities against drought, flooding, and biodiversity loss—challenges we can’t afford to ignore.

As Project Tethys unfolds, we’ll be sharing stories from the field, insights from our research, and ways you can get involved.