Modelling the impact of drainage and drain-blocking on dissolved organic carbon release from peatlands

It has been hypothesized that the trend in increasing DOC concentration in rivers draining from peat catchments is enhanced by drainage of the peat. It follows that blocking of drainage ditches could stabilise or decrease concentrations of DOC in stream water flowing from peat catchments. This study develops a model for the flux of DOC from a peat catchment in the North Pennines, UK. This model is used to predict the future DOC flux for an undrained and a drained catchment and for one where the drains were blocked. The model predicted that: i. For a pristine catchment the DOC concentration will continue to rise at an average rate of 3% per year; ii. Drained catchments export more DOC and increases are of the order of 15–33% over a 10-year period depending upon the drainspacing; iii. When drainage is blocked improvements in DOC export are predicted but the magnitude of the decrease is critically dependent upon the drain-spacing and for the larger drain-spacings no decrease may be observed. Over time, the improvements in DOC export are shown to lessen as formerly drained catchments revert to behaviour like that of a pristine catchment. Since pristine catchments are predicted to continue to lose DOC at an increasing rate the blocking of peat drains can only be considered as a medium term strategy for mediating the problem.