HYDRAULIC CHARACTERISTICS OF FOUR PEATLANDS IN MINNESOTA

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Abstract
A field study in northern Minnesota was conducted to assess the relative importance of factors that control lateral water movement in peatlands. Hydraulic gradients and groundwater velocities were measured for one mined and three unmined peatlands. Groundwater velocities were measured at shallow depths in the organic soil using the point dilution method. Hydraulic conductivities at different soil depths were estimated by applying the field measurements to Darcy's Law. Hydraulic gradients were persistent from early summer through fall and were generally less than 0.1%, a major factor governing rates of lateral water movement in undisturbed peatlands. Maximum groundwater velocities averaged 0.49 cm h−1 in the upper and least decomposed peat layers and diminished dramatically with depth and increasing decomposition. The von-Post scale of peat decomposition was found to be useful in predicting the hydraulic conductivity of peat layers. The rate of water movement at depths below 35 cm in the natural peatlands averaged less than 0.03 cm h−1. The data contribute to a better understanding of the hydrologic function of peatlands. Key words: Organic soils, peatlands, groundwater velocity, hydraulic conductivity, hydraulic gradient