Temporary streams in a peatland catchment: pattern, timing, and controls on stream network expansion and contraction

In peatlands, poorly maintained baseflows mean that network expansion during storm events can be rapid and pronounced, resulting in large changes in catchment connectivity. This has implications for the timing and magnitude of material fluxes from these environments, understanding of which is becoming increasingly important due to peatlands' significance as global carbon stores. In this study, electrical resistance (ER) technology has been used to create sensors capable of detecting the presence and absence of flow in ephemeral portions of the channel network. These sensors provide data on the patterns of network variation in the Upper North Grain research catchment, a small peatland headwater in the South Pennines, UK. Networks of around 40 sensors were deployed in autumn 2007 and summer 2008, giving a total of almost four months of high-resolution monitoring data. Drainage density in the catchment was found to vary between 1.4 and 30.0 km/km(2), suggesting significant differences in connectivity between the expanded and contracted networks. Water table depth was identified as the key factor determining the temporal pattern of streamflow at both the site- and catchment-wide scales. Spatially, network expansion and contraction occurred in a disjointed manner, following a similar pattern between events, suggesting that localized controls are important for flow generation. Spatial controls on flow generation relate to local water table levels, and include drainage area, local dissection, channel slope and gully morphology. The importance of water table as the key control on catchment connectivity suggests that potential future change in catchment water tables, associated with projected climate change or with peatland restoration by rewetting, will modify the frequency of full catchment connectivity. Copyright (c) 2014 John Wiley & Sons, Ltd.