Rewetting of a drained peatland – implications for water quality

Rewetting of previously drained peatlands in boreal regions has become a highly promoted solution to combat rising carbon dioxide emissions. By plugging drainage ditches and by raising the water table of peatlands, carbon storage is enhanced, and biological breakdown of stored organic carbon is halted. However, how the rise in water tables affects downstream water quality is not yet fully clarified. Possible effects on downstream water quality include increased mercury leaching, increased phosphorous leaching, increased dissolved organic matter and dissolved organic carbon concentrations in runoff, especially during rain events, as well as browning of downstream water bodies. These adverse effects on water quality may have implications for recipient ecosystems and drinking water production. Here we are presenting a field investigation in southern Sweden, that aims at clarifying the effects of peatland rewetting on downstream water quality. In addition to water quality parameters, we propose to measure peatland hydrology and water table depth, both before and after rewetting. The goal of the project is to inform policy makers of best monitoring practices for peatland rewetting efforts. Care must be taken to conduct thorough baseline studies at least during one - preferably two -years before rewetting. To understand the long-term effects of rewetting on downstream water quality, long time series are imperative. Monitoring should thus be continued for multiple years to decades after rewetting.