Palustrine wetlands in Lesotho are vulnerable to vegetation loss due to overgrazing and the nature of the topography, the latter leading to gully erosion exacerbated by a degraded soil structure. Degraded soils are not able to adsorb pollutants; neither can they support vegetation growth. The presence of degraded soils in wetlands thus contributes towards leaching of pollutants into nearby streams and groundwater resources. Khubelu wetland (which was the focus of this study) is a palustrine wetland that discharges water into the Khubelu stream in Lesotho. The water purification function of this wetland is pertinent since Khubelu River is one of the tributaries at the headwaters of the shared Orange-Senqu basin. This function is threatened by vegetation loss and soil degradation through overgrazing and environmental conditions like extreme climatic variations. Consequently, water released into adjacent streams from the wetland could be of low quality, further putting at risk the health of this ecosystem and users of these streams due to toxicity caused by the polluted water from the wetland. With predicted floods and/or droughts and intense heat, water temperatures may rise by up to 70% in the 21 st century according to researchers. It is believed that floods would lead to shorter residence time of water within wetlands, washing away soil with pollutants into surrounding streams before any geochemical processes that would sequester them occurs. Droughts on the other hand would lead to failure of dilution of polluted waters. Excessive evaporation due to intense heat would also leave pollutantconcentrated water behind. Since these wetlands are the headwaters of an international river, the problem of water pollution and deteriorated water resources might be regional.

The main aim of the study was to characterise the extent of soil degradation and water quality in the Khubelu wetland and assess the water purification ability in an endeavour to understand the role the wetland plays in the quality of water in rivers and streams fed by the Khubelu wetland, and also to understand how changes in climate would impact on the wetland characteristics. In situ analyses of soil and water were done followed by sampling of the same for further analysis in the laboratory using standard methods. Surface water samples were collected from two sampling points in the Khubelu stream, whereas water in the wetland was sampled from seven piezometers installed in the wetland. Three replicates of water samples were collected from each sampling point monthly over a period of one year. The water properties determined included pH,