BATHYMETRIC MAPPING AND VOLUMETRIC ANALYSIS FOR SUSTAINABLE MANAGEMENT; A CASE STUDY OF ERELU RESERVOIR, OYO, OYO STATE

ABSTRACT Sustainability of any serving waterbody remains paramount to the community benefiting from it, therefore needs to be managed. Erelu reservoir has been in existence since 1960s for the supply of potable water as a primary purpose with fishing as a secondary, however thorough evaluation has not been done to test its capacity to solve the problem of rising in water scarcity due to continuous increment of Oyo populace day by day especially in newly developing areas and places where hygienic water are not available. This project therefore aimed to look for a possible way to combat the challenge using bathymetric information as a base data. South SDE-28S+ Echo sounder plus a GPS were used for simultaneous determination of depths and positions; thereafter a data processing with the aid of Hypack, ArcMap and Surfer to produce bathymetric chart and 3D surface maps, determine depths values, Surface area and the reservoir volume. And from the processed data, it was discovered that the maximum and minimum depths were 5.89m and 0.64m respectively, with 2.11m as an average depth while the volume was 2,297,357.119792m3 as at the time of observation. This available volume can only sufficient for 16 days usage by the present populace of Oyo metropolis and can serve for months if properly manage by dredging, monitoring and expanding the tributaries entrances, continuous replacement of water back to the reservoir and rainfall effect as an addition, although the service tank is 4800m3 and cannot serve the metropolis for a day, increasing the tank to 600,000m3 is highly recommended to serve Oyo for three days consecutively and save stress of having to pumping 31times daily and 93 times in three days and also reduce unnecessary expenses. The entire area of the reservoir could not be covered during the bathymetric survey due to the presence of aquatic weeds along the shoreline and shallow areas, making them to be unnavigable. It is therefore recommended that the shoreline should be cleared from time to time to permit easy navigation and dredging exercise should be taken into consideration to increase the volume capacity of the reservoir.