FLOW REVERSALS IN PEATLANDS INFLUENCED BY LOCAL GROUNDWATER SYSTEMS

Piezometric head data from various depths were examined at two peatlan ds in Ontario, Canada and one peatland in Sweden influenced by small-s cale, shallow groundwater systems. Data from different hydrogeological settings show reversals in groundwater flow leading to discharge in t opographically high regions of peatlands in isolation from large-scale groundwater flow. It is suggested that subsurface flow within peat ca n reverse in direction in response to water deficit and water-table dr awdown. The data presented here refute the assumption that local groun dwater flow in peatlands is unidirectional and further illustrate the fact that measurable subsurface water flow can occur at depth in peat isolated from large-scale groundwater flow systems. In the light of im plicit assumptions made by many workers on water movement in peatlands , especially when connected to small-scale groundwater systems, the co nsequences of such reversals are paramount in understanding the hydrol ogy and biogeochemistry of peatlands. (C) 1997 by John Wiley & Sons, L td.