Wetland hydrology indicators of Maluti Mountains wetlands in Lesotho

Abstract

Hydric soil morphological features are generally accepted to be reliable indicators of wetland hydrology. The relationship between soil water saturation and soil morphological indices is evaluated in this study from bi-weekly water level data taken over a period of two years. The hydrological behaviour of the Bokong wetlands is described by recession in hydrographs during the low rainfall season. However, the fens and hillslope seeps (PW08, PW19, PW21, PW24 and PW32) indicate spikes under the low rainfall period, associated with subsurface flow from the surrounding catchments and streams. Wetlands PW06, PW07 and PW27 were bogs and had soil organic carbon higher than 12%. The falling water levels in the bogs suggest that the wetlands are mainly recharged by precipitation and runoff. The water level resides within the 0–500 mm depth for 80% of the monitoring time. Strong correlations are observed between soil morphological indices and cumulative water saturation. The coefficients of determination (r 2) for depth to gley matrix, depth to chroma 3 or 4, and profile darkening index were 0.74, 0.77 and 0.88, respectively. These hydric indicators therefore can be used to determine wetland hydrology. Histisols, histic epipedons, umbric surfaces, thick dark surfaces and loamy gleyed matrix occur.

Keywords: cumulative saturation, hydric soils indicators, morphological indices, wetland hydrology