Physio-chemical characteristics, isotopic signatures and hydrochemistry of two contrasting wetlands in two agro-ecological zones of Lesotho

Agricultural activities; grazing and cropping are thought to be the major contributors to non-point wetland pollution and other land degradation forms in the highlands and foothills while industrial effluents and domestic waste disposal are thought to contribute significantly to wetlands’ pollution in urbanized and industrialized lowlands. In Lesotho wetlands are important for livestock grazing and the problems related to wetlands management, in particular soil erosion, are related to over- grazing. There is sparse data on the physico-chemical characteristics of wetlands in Khalong-la-Lithunya and Ha-Matela catchments, including, soil organic carbon pools and the vegetation isotopic signatures of the wetlands. Hence an investigation was conducted to assess the soil physico-chemical characteristics and hydrochemistry of the surface waters and vegetation isotopic signatures in order to assess the extent of human induced degradation at Ha-Matela and Khalong-la-Lithunya wetlands. The results indicate that on both sites the soils mostly exhibit a reddish color, which is not typical of wetland soils, except a few points at Ha-Matela. The silt to clay ratios indicate that the Ha-Matela soils are highly weathered while the Khalong-la-Lithunya soils are weakly (or not weathered). The results further indicate that Khalong la Lithunya wetlands are richer in organic carbon (organic carbon ranges between 2.1 and 5.23% and organic carbon pool ranges between 4.0 and 23.9kg/m2) and less degraded ( s13 C= -28.62, S15N= -2.81) compared to Ha-Matela wetlands (organic carbon= 1.18-2.56%, organic carbon pool- 4.65-19.23Kg/m2, s13C = -12.78 and S15N = 3.60). Water quality parameters were found to be below WHO and European Union standards for drinking water (WHO). The results of step multiple regression analysis suggested that in wetlands management close attention should be paid to sand, organic carbon, potassium, bulk density available water holding capacity, available phosphorus and pH for Ha-Matela wetland and for Khalong-la-Lithunya wetland attention should be paid to sand organic carbon and available water holding capacity so as to prevent further degradation of wetlands.