Flow effect of Kainji Dam on the Distribution of Water Hyacinth in Kolo Creek, Bayelsa State of Nigeria

Abstract

Water Hyacinth (Eichhornia crassipes) is an exotic species whose emergence in the Niger Delta region of Nigeria became noticeable at least within the last two decades. The menace of the water weed in the Niger Delta in recent times has been an issue of Global concern. This must have prompted the appearance in the World Bank (1995) reports on the prioritization of major environmental problems in the Niger Delta, of water hyacinth as invasive exotic species together with Nypa palm. The socio‐economic and environmental consequences of this invasive weed to the stream users, as well as to the stream ecosystem, leave much to be done. This study focuses on measuring the flow effect of the Kainji dam on the distribution of water hyacinth in the Niger Delta. Run‐off data were obtained from secondary sources for Onitsha and Lokoja stations. Differences in annual means for pre‐dam and post‐dam run‐off were statistically significant [t‐stat = 2.53 > t‐statcrt(0.05) = 2.228] for Onitsha and [t‐stat=2.96>t‐statcrt(0.05) = 2.228] at Lokoja. The cross‐sectional area of the affected stream, velocity and discharge were measured for each segment of Kolo Creek and Esoghoni creek and correlated with area covered by the macrophyte. Our study showed that flow velocity and discharge negatively correlated with the area covered by macrophyte in both wet and dry seasons. The large hydro power electricity dam has apparently affected the flow regime of the downstream sections of the Niger and consequently altered the discharge and the wetted perimeter of the streams in the area creating an enabling environment for the water hyacinth to strive.