Impacts of reduced flows on the macroinvertabrates and riverside resources in Malibamatšo river; lesotho

Construction of large dam on river has detrimental effect on the aquatic ecosystem thus impacting the river health and availability of other riverine resources. This study aims to determine the effects of the regulated flows on the macro-invertebrates and riverine resources in the Malibamatšo River. The study determines the changes in abundance of the riverine resources as well as the macroinvertabrates with respect to discharge before and after contraction of Katse Dam. Data about the invertebrates was collected and analysed by South African Scoring System (SASS) and by Ms Excel 2007, the indigenous knowledge about the river conditions before and after the construction of the Katse dam on the Malibamatšo River was collect by questionnaire-based interview and there after analysed using Statistical Program for Social Sciences (SPSS) and Ms Excel 2007. More than 70% the indigenous community indicated that most invertebrate are present in summer (which is the rainy season). The community also uses the river for several purposes such as fishing, making laundry, drinking water for animals and swimming. About 50% of the population argued that the river and invertebrates conditions have not changed since the construction of the dam. However the historical data indicates that’s the trend of the Average Score Per Taxa (ASPT) calculated from the SASS results indicate that both upstream and downstream is decreasing, which simply implies that the river condition is deterioration although it is at a slow rate. Nonetheless, management actions have to be put in place for maintaining the river health before it is completely beyond restoration to the healthy state. That is, there need to be change in the operation of the dam releases to fulfill the downstream requirements so as to give room for improvement of the river health.