[WATER][RESOURCE][ENVIRONMENT] Trace gas cycling and soil carbon budgets in rewetted upland mires of Exmoor National Park

The uplands of Exmoor National Park receive a considerable proportion of the annual rainfall that supplies water to >500,000 consumers in the River Exe catchment. This area also contains large tracts of degraded peatland that were damaged by drainage and peat cutting in the 19th and 20th centuries. South West Water plc manage the water resources of the Exe Catchment and are investing in mire restoration for the purpose of improving the quality and quantity of water supplies. Amongst the numerous benefits of mire rewetting is the potential to alter the balance of trace gas exchange with the atmosphere to cause a net reduction in Global Warming Potential (GWP). Landowners at present do not receive financial reward for converting degraded moorland back to a natural wet state. They receive no monetary benefit for improvements in water quality or quantity, nor are they paid for enhancing rates of soil carbon sequestration or a net reduction of greenhouse gas emissions. The motivation for this study is South West Water plc's need to quantify net changes in GWP and improvements in water quantity and quality due to rewetting of upland mires for the purpose of securing funds to reward landowners that make areas of degraded peatland available for restoration. A project operated by the Environment Agency and Exeter University (and funded by South West Water plc) is underway to address the water supply and quality questions. The Bristol Open CASE PhD student will study cycling of the infrared absorbing gases carbon dioxide, methane and nitrous oxide in the same two headwater catchments that have been instrumented for the water study. The aim of this project is to quantify atmospheric and fluvial fluxes of these key greenhouse gases before and after ditch-blocking to determine the net impact of mire rewetting on GWP. An important aspect of the study will be to estimate errors and uncertainties in the flux data, more specifically, the timeline for establishing biogeochemical equilibrium in the soils after rewetting and the range of inter-annual variation in pre-restoration baseline fluxes. The former issue will be addressed using changes in the stable isotope composition of methane which varies with trophic and aeration status in peatlands and can be used to monitor the restoration of soil biogeochemical function. During the study, flux measurements will be made at stations in adjacent unrestored catchments to assess inter-annual variability in pre-restoration baseline fluxes because it will be possible to measure only one year of surface and fluvial fluxes before ditch-blocking begins in the test catchments. The PhD student will work with staff at South West Water plc to establish a monetary value (based upon trading of CO2 equivalents) for net changes in GWP. Pending the final outcomes of this study, the information may be used by the CASE Partner to negotiate monetary rewards for landowners in the 2015-2020 water price limits set by the Water Services Regulation Authority (Ofwat). The motivation is to establish a long-term system of incentives that will encourage more landowners to allow areas of degraded peatland to be restored for the wider benefit of society.