The Heath of the River

While the River Sid faces many physical and invasive threats, local volunteers and scientists constantly monitor its "vital signs." Understanding the water quality helps us protect the delicate ecosystem that remains.

1. The "Canaries in the Coal Mine": River Flies

To assess if the water is healthy, the Sid Valley Biodiversity Group conducts regular surveys of river fly invertebrate populations.

• Biological Indicators: Nymphs and larvae of species like mayflies, stoneflies, and caddisflies act as indicators of river health.

• Current Status: Recent surveys have yielded healthy populations of these target species, suggesting a functioning ecosystem that is "reasonably healthy," though not pristine.

• Predators: The presence of kingfishers is a positive sign, as they require clean, well-oxygenated water with a steady supply of small fish.

2. Measuring Water Quality: TDS and Temperature

Beyond biology, chemical and physical measurements provide a clearer picture of the river’s condition.

• Total Dissolved Solids (TDS): This measures the concentration of dissolved substances in the water. Levels generally increase as the river flows downstream.

  • Upper Catchment (Plyford): Low readings, usually under 70 ppm.

  • Mid-River (Sidbury/School Weir): Higher readings, often between 150–200 ppm.

  • Trouble Spots: Burscombe Brook and Woolbrook often record highs of 270–288 ppm.

• Temperature Spikes: In July and August, water temperatures have been recorded reaching 18^ to 20^ on certain tributaries, which can stress aquatic life.

• Turbidity: While normally low, the water becomes highly "turbid" (cloudy) after heavy rain as soil washes in from steep fields.

3. Sources of Pollution

The river acts as a collection point for both rural and urban runoff.

• Agricultural Runoff: Pesticides, herbicides, fertilisers, and silt from poor maize cropping or "contract farming" practices.

• Urban Runoff: Road salt, vehicle tire abrasion, garden chemicals, and potential issues from historical landfill sites or sewage.

• The "Red Sid": Intense rainfall on steep gradients washes soil and nutrients into the system, turning the river its iconic red colour.

4. The Biodiversity Crisis: Species in Decline

Despite the "reasonably healthy" water rating, several key species have vanished or are in serious decline due to habitat loss and physical barriers.

• Missing Mammals: Water voles are now considered a lost species along the Sid.

• Vanishing Birds: Snipe and water rail populations have declined.

• The Fish Barrier: School Weir prevents Atlantic Salmon, Sea Trout, and European Eels from reaching upstream spawning grounds.

5. Managing the Future: Opportunities for Change

There are several proposed ways to improve the River Sid for future generations:

• Removing Barriers: Experts suggest removing or modifying barriers to ensure unimpeded fish passage.

• Natural Solutions: Implementing SuDS (Sustainable Drainage Systems) like rain gardens and water butts in Sidmouth to reduce urban runoff.

• Habitat Restoration: Replanting hedgerows and creating new wetland habitats to replace those lost to development.

• Coastal Management: Shortening coastal structures to allow natural sediment (sand and gravel) to move back onto East Beach.