Water-level dynamics in natural and artificial pools in blanket peatlands

Perennial poolsare common natural features of peatlands, and their hydrological functioning and turnover may be important for carbon fluxes, aquatic ecology, and downstream water quality. Peatland restoration methods such as ditch blocking result in many new pools. However, little is known about the hydrological function of either pooltype. We monitored six natural and six artificial poolson a Scottish blanket peatland. Poolwater levels were more variable in all seasons in artificial poolshaving greater water level increases and faster recession responses to storms than natural pools. Poolsoverflowed by a median of 9 and 54 times poolvolume per year for natural and artificial pools, respectively, but this varied widely because some large poolshad small upslope catchments and vice versa. Mean peat water-tabledepths were similar between natural and artificial poolsites but much more variable over time at the artificial poolsite, possibly due to a lower bulk specific yield across this site. Poollevels and pool-level fluctuations were not the same as those of local water tablesin the adjacent peat. Pool-level time series were much smoother, with more damped rainfall or recession responses than those for peat water tables. There were strong hydraulic gradients between the peatand pools, with absolute water tablesoften being 20–30 cm higher or lower than water levels in poolsonly 1–4 m away. However, as peathydraulic conductivity was very low (median of 1.5 × 10−5 and 1.4 × 10−6 cm s−1 at 30 and 50 cm depths at the natural poolsite), there was little deep subsurface flowinteraction. We conclude that (a) for peatrestoration projects, a larger total poolsurface area is likely to result in smaller flood peaks downstream, at least during summer months, because peatland bulk specific yield will be greater; and (b) surface and near-surface connectivity during storm events and topographic context, rather than poolsize alone, must be taken into account in future peatland pooland stream chemistry studies.