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Near-surface macropore flow and saturated hydraulic conductivity in drained and restored blanket peatlands

Wallage, Z.E., Holden, J.
Soil use and management 2011 v.27 no.2 pp. 247-254
infiltrometers, macropore flow, macropores, peat, peatlands, runoff, saturated flow, saturated hydraulic conductivity, soil water, water management, water table
The impacts of blanket peatland management on water tables, near-surface macropore flow and saturated hydraulic conductivity were investigated using automated dipwells and mini-disc tension infiltrometers. Three neighbouring hillslopes which were undisturbed, drained and restored by drain blocking were studied. Mean water table depths at the undisturbed sites were slightly shallower than at the restored site and water tables at both sites were significantly shallower relative to the drained treatment. Through time, however, the water table at the restored treatment behaved in a markedly different way to that at the undisturbed site. Water tables reached the peat surface for only 2% of the time for the drained and restored treatments compared to 18% for the undisturbed treatment. The proportion of runoff flowing through macropores in the near-surface layers of the peat was found to be large (≥60%) across all three treatments, yet functional macroporosity was found to be significantly greater in the undisturbed peat relative to the two other treatments. Meanwhile, saturated hydraulic conductivity was found to be significantly higher at the restored treatment relative to the two other treatments, with mean conductivities ca. 1.5 times greater, suggesting a form of heightened soil-water interaction. Combined, the results indicate that although restoration by ditch blocking may result in a relatively successful water table recovery, there may not be the full reinstatement of peatland hydrological processes.