Towards effective Hydrological Measurements downstream of Oyan dam
In 2011 the National Water Resources Institute (NWRI), Kaduna developed a Concept Note on Reservoir Sedimentation Study for Bakolori, Goronyo and Oyan dams. The study thrust is in five areas: Reservoir depth sounding, Downstream Studies, Hydrological Studies, Remote Sensing/GIS Applications and Environmental/ Socio-economic impacts assessments. A focus group on each area of the Reservoir Sedimentation study was constituted. NWRI held collaborative meetings with participating staff of selected organizations in Nigeria that are to implement the study. NWRI Management had undertaken a planning visit to these dams and the supports of the River Basin organizations that own the dams was secured. On 24th – 27th. May, 2011, the author participated in the Downstream Study group planning visit to Oyan Dam. During the visit, the downstream study group had a meeting with the Management of the Ogun-Oshun River Basin Development Authority (OORBDA) to discuss the study and obtain relevant documents like rating curves of existing gauging stations, maps etc. Also there was a visit to Oyan Dam reservoir, the GPS readings of benchmarks at the dam site were taken and the Oyan river system downstream of the dam was explored to determine along the main channel suitable sections for discharge measurement and Sediment sampling for onsite determination of sediment concentrations. Ten sites on the Oyan and Ogun rivers system were visited noting their hydro-environmental peculiarities. A brief overview of some of the sites is highlighted in the paper. Five locations were identified as suitable for discharge measurement and sediment sampling.