HYDRAULIC CONDUCTIVITY AND RELATED PHYSICAL PROPERTIES OF PEAT, LOST RIVER PEATLAND, NORTHERN MINNESOTA

Abstract

We measured hydraulic conductivity (K), bulk density, and humification of peat in three soil profiles at a spring fen-raised bog complex in the Lost River Peatland, northern Minnesota. Piezometers were installed at saturated depths ranging from 0.5 to 3.0 m on a raised bog, its external fen margin, and an adjacent spring fen, and field K was determined by time-lag methods. Field K ranges from 2.5 x 10−4 to 5.6 x 10−3 cm/s on the bog, from 1.5 x 10−3 to 2.6 x 10−2 cm/s at the fen margin, and from 6.7 x 10−4 to 1.6 x 10−2 cm/s on the spring fen. The K determined for partially decomposed peat deeper than 1 m is 2 to 6 times greater than previously reported in the literature. There appears to be little correlation of K with depth, as suggested by most other workers who have investigated only the uppermost “active‘’ layer, about 50 cm deep. Laboratory analyses of K from peat cores show that the ratio of horizontal K (Kh) to vertical K (Kv) is highly variable throughout the peat column. Kh is generally one to two orders of magnitude greater than Kv. Bulk density values are similar to those found for other moderately decomposed peats in Minnesota, ranging from 0.06 to 0.14 g/cm3. Bulk density and humicity do not statistically correlate with depth or with K for the peats in the Lost River Peatland. This study suggests that humified peat can transmit groundwater more rapidly than previously thought and that the interaction between groundwater in the peat and associated surface waters can be significant.