The sediment dynamics in a small 2nd order catchment of River Awba in the territory of the University of Ibadan, Nigeria was investigated between January and December 2012. The river was gauged by daily measurements of water level as well as sampling of water for determination of suspended sediment load. In this regard, apart from weekly sample, twelve (12) storm flow events which occurred during the day were sampled for determination of suspended sediment concentration. The results showed that during the storms the suspended sediment concentration varied between 636 mg/l in May and 3641.5 mg/l in September, with a mean of 2136.8 mg/l. Also, the value of monthly suspended sediment yield ranged from 10.85 kg in January to 288.4 kg in October with a mean of 89.5 kg. The variability in monthly sediment load closely followed the trend of monthly rainfall in the study area. However, in order to minimize the storm runoff and sediment load generated from the rainstorms events, the paved surfaces within the study catchment should be grassed with the planting of some few tree species. This could further reduce the rate of floods occurrence.
High demand for water is driving potentially unsustainable practices and competition for water resources between various sectors in developing areas. As a result of improved quality of life and population growth, increase in demand for fresh water is anticipated in all African countries in all sectors, over the next 10 years. This study examines the effects of dry season irrigation farming (fadama) on the physical and chemical quality of the River Osin which receives both surface and subsurface flow from irrigated areas in the Upper Osin Catchment, Kwara State, Nigeria. A total of 90 samples were obtained from Upstream (UPS), Irrigated area (IRG) and Downstream (DNS) segments of the river in the dry and rainy seasons. Water samples were analysed for pH, conductivity, total dissolved solids (TDS), suspended solids, dissolved organic matter (DOM), pesticides (ionic basic type), Na+, K+, Mg2+,Cl-, NO3-, PO43-, Ca2+ and HCO3-. The results indicate that values of agricultural pollutants such as pesticides (CuSO4), NO3- and PO43- were significantly higher at IRG than at UPS, and decreased slightly at DNS, while all other anions and cations except DOM reached peak values at DNS. Agricultural pollutants (NO3-, PO43- and pesticides) contributed significantly to poor water quality observed at IRG and DNS segments but the values are within acceptable tolerance range at UPS. The findings further indicate that irrigation practice degrades the quality of water at IRG and DNS segments. As a result, a holistic approach to agriculture and water resource management is recommended to ensure sustainable water resources development in the catchment.
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