Peatland Hydrology: Stopping the Bleed
Degraded peatlands are a massive source of UK greenhouse gas emissions. Restoring them via hydrological intervention (drain blocking) shifts them from net-emitters to net-sinks.
The Grips Problem
Post-WWII agricultural policy incentivised the digging of 'grips' (drainage channels) across upland peat bogs to 'improve' them for sheep grazing and grouse moors. This lowers the water table, exposing anaerobic peat to oxygen. The result is rapid oxidation and the release of massive quantities of CO₂ and dissolved organic carbon (DOC) into the water supply.
| Condition | Estimated Flux (tCO₂e/ha/yr) | Primary Mechanism |
|---|---|---|
| Actively Eroding / Hagg | +15.0 to +24.0 | Particulate organic carbon loss, massive oxidation |
| Drained (Grips) | +10.0 to +12.0 | Lowered water table, oxidation |
| Modified (Grass dominated) | +3.0 to +5.0 | Lack of peat-forming sphagnum |
| Restored / Near Natural | -0.5 to -3.0 | Anaerobic sequestration via Sphagnum growth |
Intervention: Drain Blocking
The primary mechanical intervention is blocking the grips to raise the water table to within 10cm of the surface.
- Peat Dams: The most cost-effective method on slopes < 3%. An excavator uses local wet peat to create impermeable plugs every 10-20 meters.
- Plastic/Timber Piling: Necessary on steeper gradients or where flow rates are high, to prevent blowout before the hydrology stabilizes.
- Coir Rolls & Sphagnum Inoculation: In severe gullies, coir rolls slow the water flow, creating silt traps which are then manually inoculated with Sphagnum moss plugs (e.g., S. papillosum, S. capillifolium).
Peatland Code (UK)
Unlike the Woodland Carbon Code, the Peatland Code currently only pays for emissions reduction, not sequestration. If you move a hectare from Drained (+10t) to Restored (-1t), you generate 11t of avoided emissions per year. Run the Flux Model.