HYDRO-BIOLOGICAL CHARACTERISTICS OF THE BUI DAM AREA OF THE BLACK VOLTA

Abstract

The hydro-biology of the Black Volta near the Bui Dam was studied during the pre- and post-impoundment periods between February 2011 and December 2012. The primary objective was to assess the ecological impacts of the dam on the hydro-biological factors and to provide data for monitoring the hydro-biological characteristics of the newly created Bui reservoir. Two sampling stations at Bui and Bamboi were selected to represent the upstream and downstream stations, respectively. The phytoplankton and zooplankton groups were significantly (p < 0.05) higher at the upstream station than at the downstream station indicating the impact of the impoundment on the downstream plankton ecology. The study also showed that chlorophyll a and some species of phytoplankton significantly differed (p < 0.05) between the pre- and post-impoundment periods. There was generally a low macrobenthic invertebrate diversity in the Black Volta. Chironomidae dominated the benthic samples. The seasonal distribution showed that the post-wet season recorded the highest invertebrate numbers, while the wet season recorded the lowest numbers. Chironomidae increased from 15 during the pre-impoundment period to 19 during the late post impoundment period. Ephemeroptera numbers, however, increased from 7 during the pre-impoundment period to 11 in the post-impoundment period. There were, however, no significant differences (p > 0.05) in the numbers of the macro-invertebrates between the pre- and post-impoundment periods. Hence, the damming of the Black Volta at Bui had no significant impact on the abundance and distribution of benthic invertebrates. The study, therefore, revealed that out of the 4 hydro-biological factors (chlorophyll a, phytoplankton, zooplankton and microbenthic invertebrates), there was an impact of the impoundment on chlorophyll a and phytoplankton abundance.