Assessment of the water balance of the Barekese reservoir in Kumasi, Ghana

The Barekese Reservoir constructed across the Offin River provides 80% of the total public pipe borne water supplied to the Kumasi metropolis and its environs. The reservoir was designed to produce both potable water and hydropower, however, the hydropower component has not been implemented since its construction in 1971.There is also reported land cover degradation in the catchment area which has the propensity to alter the hydrologic cycle and hence runoff into the reservoir. A 10 year water balance has been assessed for the Barekese Reservoir using an integrated Remote Sensing and GIS approach for estimation of surface runoff based on Soil Conservation Service Curve Number (SCS-CN). The SCS-CN model was calibrated against observed discharges recorded at Offinso located 10.3km upstream from Barekese and the result of the calibration used to simulate runoff into the reservoir. The SCS-CN model produced an R2 value of 0.84 and an efficiency of 82.68%. Monthly observed reservoir levels were used for the calibration and validation of the water balance model. The water balance model produced an R2 value of 0.84 and an efficiency of 81.9%. The monthly water budget revealed that total catchment runoff and direct precipitation respectively constituted 94.32% and 5.68% of the inflows while spilled water, water withdrawal and evaporation respectively amounted to 72.19%, 20.85% and 6.96% of the outflows. This result reveals that the reservoir is being underutilized. The current average production of treated water is 109,000m3day but the reservoir can safely yield the design capacity of 220,000m3day and an additional average hydropower of 368.6kW in six months during the rainy season provided the economic analysis for the hydropower generation is found to be justifiable.Keywords: Water balance, Barekese Reservoir, SCS-CN model, Offinso, Hydropowe

Effects of Different Solid Loading Rates of Faecal Sludge on the Dewatering Performance of Unplanted Filter Bed.

The aim of this study was to investigate which Solid Loading Rate (SLR) of faecal sludge will best improve the dewatering performance of selected sand with particle sizes range of (? 0.1 ? 0.5) mm raised on bench scale filter beds. Public toilet sludge  and septage collected from suction trucks discharging at Dompoase stabilisation  ponds in Kumasi , Ghana, mixed in the ratio of 1:1, 1:2 and 1:3 by volume representing SLR1, SLR2 and SLR3 respectively, were used for the dewatering. Percolate volume was measured every 24 hour. The faecal sludge of SLR1, SLR2 and SLR3 dewatered at average dewatering times of 7, 5 and 4 days respectively. Removal efficiencies of the different solid loading rates though very high for TS, SS, TVS, COD, DCOD, NH3-N, did not show any significant difference. Organic matter build up in the top 10cm of the filter bed was least in SLR3. Again SLR3 showed the highest potential for annual generation of biosolids at 438, 421 and 379 (kg/m2 year) for SL3, SLR2 and SLR1 respectively. Therefore SLR3 of faecal sludge is recommended for dewatering on the selected filter bed. Key words: Faecal sludge, solid loading rate, dewatering time, filter bed, percolate