Water pH experiment on the Migneint

The river Conwy catchment area is a unique study site as it is solely peatland influenced, there is no mineral soil and therefore any changes that are observed are cannot be caused mineral soil.  

The Migneint is a blanket bog in southern Gwynedd in North Wales, within the Migneint/Arenig/Dduallt SAC. Blanket bog habitats are vitally important as carbon storage sinks and therefore for climate regulation as they store vast amounts of carbon a peat

When we arrived at the Migneint, we were presented with a plot scale Defra funded experimental study that is looking at alkalination and acidification in blanket peat. We got to work by continuing this experiment by adding two watering cans of acidic water,  two of basic water and two plain water as a control site to test for the long term effects of pollutants in rain on blanket peat. 

 A view over the northern part of the Migneint. The coloured markers indicate different  treatment plots. Red = Acid, Blue = Alkaline White = Control. Boardwalks make access to the plots easier

 

Over the last 200 years, some great biogeochemical changes have occurred through sulphication of soils as a result of fossil fuel burning leading to the release of Sulphur dioxide forming sulphuric acid on deposition. This was a major problem throughout central Europe and Norther England. Peatlands north east of Manchester were badly affected due the prevailing winds. Acid rain is however not much of the problem anymore in Europe. Greenhouse gas measurements were taken after treatments using the using the static chamber technique and pore water samples were taken using rhizons.

The toolkit of a wetland scientist. Notice the clear chamber to measure gross photosynthetic potential.

  Watering can to add treatment and dark chamber to measure soil respiration

 
We then headed to the Llyn Conwy, the head waters of the river Conwy drain the norther part of the Migneint. Between the 1930s and 1970s, however, the digging of drainage ditches across a large part of the peat area has resulted in widespread water table drawdown, exposing the peat to greater oxygen levels and potentially leading to accelerated decomposition and carbon loss. One of the ditches was about 1 meter in width and drained straight into the lake.  

 Llyn Conwy natural lake managed by Welsh Water as a reservoir supplying the needs of the upper conwy valley including Llanrwst and Betws-y-Coed. It is the biggest lake on the Migneint and the source of the river Conwy.

River Conwy

Ditches were dug in the hope that the less wet surface would facilitate sheep grazing but the theory was abandoned as it did not seem to work. It is proposed that these these ditches should now be in-filled as rising levels of DOC leaching into the water can have serious cost implications for Welsh Water who manage the water treatment works and health implication for the public. Natural streams do not leak as much DOC as mad-made ditches. It is hoped that restoring the Migneint by blocking drainage ditches will alleviate flooding in the upper Conwy valley as 5 million has been spent on flood defences in recent years. Bog restoration is a relatively cost effective method of flood control.

Drainage ditch sometime called a "grips" have been subject to widescale blocking over the northern part of the Migneint to reverse oxidation and DOC losses.