Spatial variability of hydraulic conductivity and bulk density along a blanket peatland hillslope

This article presents the results of a field investigation of saturated hydraulic conductivity K_sat and bulk density (ρ_bd) in an Atlantic blanket bog in the southwest of Ireland. Starting at a peatland stream and moving along an uphill transect toward the peatland interior, ρ_bd and K_sat were examined at regular intervals. Saturated horizontal hydraulic conductivity (Kh_sat) and vertical (Kv_sat) was estimated at two depths: 10–20 and 30–40 cm below the peat surface, whereas ρ_bd was estimated for the full profile. We consider two separate zones, one a riparian zone extending 10 m from the stream and a second zone in the bog interior. We found that the K_sat was higher (~10^–5 m s^–1) in the bog interior than that in the riparian zone (~10^–6 m s^–1), whereas the converse applied to bulk density, with lowest density (~0.055 g cm^–3) at the interior and highest (~0.11 g cm^–3) at the riparian zone. In general, we found Kh_sat to be approximately twice the Kv_sat. These results support the idea that the lower K_sat at the margins control the hydrology of blanket peatlands. It is therefore important that the spatial variation of these two key properties be accommodated in hydrological models if the correct rainfall runoff characteristics are to be correctly modelled. Stream flow analysis over 3 years at the peatland catchment outlet showed that the stream runoff was composed of 8% base flow and 92% flood flow, suggesting that this blanket peatland is a source rather than a sink for floodwaters. Copyright © 2011 John Wiley & Sons, Ltd.