Assessing the Effects of Ditch Blocking on Dissolved Organic Carbon and Rainfall-Runoff Regimes: Results From a Climatically Marginal Shallow Peatland

This study addresses an evidence gap on the restoration potential of climatically marginal shallow peatlands by investigating short-term (five years post-rewetting) effects of ditch blocking on runoff and water quality. Results from two sites in south-west England (UK) showed reductions in peak flows ranging from 29 % to 32 % after rewetting, indicating modifications of rainfall-runoff regime in these catchments as a consequence of rewetting. In addition, a statistically significant reduction in total rainfall-runoff event discharge was observed at one of the study sites. The findings suggest an increase in the temporary storage of flow during rainfall-runoff events and an overall attenuation of storm hydrographs. Water quality responses to rewetting did not show any significant change in either DOC or colour concentrations during rainfall-runoff events. It is likely that such behaviour is due to the spatially limited success of rewetting interventions in significantly raising water tables in these shallow peatlands, and thus to a limited reduction in decomposition of vegetation and peat. No significant changes in DOC loads (normalised by rainfall) leaving the catchments were observed either. It is possible that a longer post-rewetting period will be needed to see any change in water quality, as vegetation responds in the longer (> 5 years) term.