Saturated hydraulic conductivity of boreal peat and its relationships with peat properties and sampling depth

The boreal region is a significant peat-forming area. With peat, there lie other natural resources, including mineral ores and fossil fuels needed by our economy. However, mining for mineral resources or any other activity that leads to large-scale groundwater extraction in the near vicinity or underneath the mires can alter the water levels in the overlaying ecosystems and thus have a damaging effect on them, raising concerns about the mires' preservation. Peat itself may isolate surface vegetation from drainage caused by nearby mining when its hydraulic conductivity is sufficiently low. More is known about the hydraulic properties of the uppermost layers of the peat column, but there is very little data about deeper, generally more decomposed peat layers that may potentially act as drainage barriers. Carrying out in situ hydraulic conductivity tests in less conductive peat can be laborious and time-consuming, and not always practical. This research aims to study and verify statistical relationships between easy-to-measure peat properties and hydraulic conductivity over the entire peat column, covering the knowledge deficit that is important in the context of indirect drainage effects related to mining or any other large-scale groundwater extraction. For that, we sampled peat and conducted in situ saturated hydraulic conductivity tests in several mires in northeast Estonia to gather information about the hydraulic properties of boreal peat. Collected data were fitted with linear mixed-effects models to link hydraulic conductivity with the degree of decomposition, dry bulk density, depth of measurement, and peatland growth phase. The results indicate that these parameters are strongly correlated with saturated hydraulic conductivity and can serve as predictors of this parameter. Constructed statistical models exhibit relatively high explanatory power and show potential usage for characterizing the hydraulic conductivity of peat. The findings of this study may be helpful in the efforts of mire conservation.