A review of the effects of dams on the hydrology, water quality and invertebrate fauna of some Nigerian freshwaters

Abstract

In this paper, the effects of dams on the hydrology, water quality and invertebrate fauna of some Nigerian inland waters were reviewed. The freshwaters considered include Awba Reservoir (Oyo State), Shiroro Lake (Kaduna State), Moro Lake (Kwara State), Aiba Reservoir (Osun State), Ikpoba Reservoir (Edo State), Onah Lake (Delta State), Tiga Lake (Kano State), Alau Lake (Borno State), Kainji Lake (Niger State) and Pan Lake (Plateau State). Dams negatively impacted the hydrology of the downstream waters by obstructing the flow of water from the reservoirs and quantitatively reducing the discharge (volume) of the receiving waters. The physico-chemical water quality of the surface freshwaters was enhanced as water flowed towards the dams and sediments were trapped in the reservoirs. In terms of biodiversity of invertebrates, dams positively enhanced the community structure of zooplankton but adversely affected that of the benthic macro-invertebrates at the deepest point of the reservoirs/lakes. On a general note, the dams can be considered as conservation apparatus for water quality and freshwater invertebrates in spite of their short comings. Their continued significance along a river course should however be periodically evaluated through environmental audits, and when necessary, decommissioned in the overall interest of conserving freshwater biodiversity in their respective ecological systems.

Keywords: biodiversity, conservation, dams, hydrology, invertebrates, water qualities