ABSTRACT

The biggest threat to reservoirs after their construction, which reduces their capacity, life cycle and water quality, is sediments carried by the inflowing streams. The study on the assessment of the impact of sediment deposits in water reservoir: a study of the National Root Crop Research Institutes' Dam Umudike was conducted, the impact of sediments on the soil physical and hydraulic properties, the water quality and the storage capacity of the dam reservoir were analyzed. The textural class of the soil was predominantly salty clay, the results of the water quality assessment of the reservoir at the beginning and peak of the rainy season showed that all the parameters analyzed were all within the WHO and FAO prescribed standards. There was no much changes in the physical properties of the water, except the turbidity which increased drastically from the range of 5.ONTU to 7.6NTU towards the downstream at the beginning of rainy season, with mean values of 6.5±O.O7NTU(morning), 6.6+O.O7NTU(afternoon), to the range of 6.ONTU to 8.2NTU towards the downstream at the peak of the rainy season, with mean values of 7.1±O.21NTU(morning), 7.4:EO.21NTU(afternoon). The analysis also showed that E. Coli was detected in a traceable amount, having mean values of 1.87x10 6±9.90x10 8mg/l(morning), 1.73x10 6±9.90x10 8mg/l(afternoon) at the beginnin of the rainy season and mean values of 1.71 xl 06+ 1.41 xl 0 8mg/l(morning), 1 .7x 106± 1.41 xl 0 mg/l(afternoon), therefore renders the water unfit for consumption. The storage capacity at the beginning and peak of the rainy season are 229.78m3and 218.50m3, respectively. It was expected that the volume of water at the peak of the rainy season would be more owing to the fact that more rainfall events had taken place. This is not so because 11.lm of the effective capacity has been occupied h silt and the reservoir have silted by 4.9% throughout this period. The best engineering solution to the problem of the dam is constant monitoring and desalting the dam at regular intervals. This will always maintain the storage capacity of the dam at optimum level and prolong the life of the reservoir. The following methods can be operated to remove sediments from reservoirs: sluicing, dredging, and putting up vegetation at reservoir area. Water from NRCRI Dam reservoir may undergo sedimentation, filtration and chlorination processes as the case may be, so as to disinfect the water from any form of contamination.