DISSOLVED SEDIMENT DELIVERY BY THE SAMARU STREAM INTO THE AHMADU BELLO UNIVERSITY RESERVIOR

(A CASE STUDY OF ZARIA, NIGERIA)

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Author

Presented To

Department of Environmental Design

ABSTRACT
This study assessed the dissolved sediment delivery by the Samaru stream into the Kubanni reservoir by monitoring the stream for seven months. The study assessed the dissolved sediment concentration, stream discharges using the USDH 48 sampler to collect sediment sample, an estimate of the dissolved sediment yield and the dissolved mineral component of the sediment by the use of an XRF analysis.The AV method was employed for the discharge measurement of the Stream which gave a mean value of 0.2528m3/s and an annual total discharge value of 4,850,232m3/yr. The lowest discharge of 0.057m3/s was recorded in April and the highest discharge of 4.133m3/s was recorded in August. Regressing rainfall on discharges shows that there is a strong direct relationship between the two at 0.05 significant levels. The relationship is strong because both r (0.913) and r2 (0.834) values are significantly high. Dissolved sediment concentration (Cd1) values obtained vary from a minimum value of 20mg/l to a maximum value of 120mg/l with a mean value of 58.87mg/l and total sum of 4180mg/l.The rating equation relationship shows that there is a weakbut direct relationship between Cd1 and Q at 0.05 significant level because both values of r (0.122) and r2 (0.015) are low. Derived dissolved sediment discharge (Qd) obtained vary from a minimum value of 1.14mg/s to a maximum value of 325.44mg/s with a, mean value of 44.52mg/s and a total value of 3162mg/s. Relating Qd with Cd1 shows that there is direct relationship between the two with the values of r (0.545) and r2 (0.296) and also, Qd and Q were related and the rating curve gives a very strong relationship with a straight line starting from the origin and both values of r (0.866) and r2 (0.749) are high. A totalvalue of 174,000 kg/yr was produced as the dissolved sediment yield of the stream with a Channel Sediment Yield (CSY) of 174 tons/yr. vii The XRF analysis identified a total of 17 mineral compounds and elements with varying degree of concentrations ranging from as low as 0.001mg/l for Re2O7andV2O5 to 8.88mg/l for CaO in the compounds and as low as 0.0 for Re to 9.50mg/l for Ca in the elements. 11 of the compounds and elements identified are of heavy metals with nickel (Ni) as the most toxic with a mean concentration value of 0.08mg/l while the WHO (2011) and NSDQW recommended standards for drinking and domestic use are 0.02mg/l and 0.07mg/l respectively and the limits to discharges into a stream is below 1mg/l which is therefore, relatively above the recommended standard for drinking and domestic use but below the standard for discharges into the stream. Other elements identified to be above the recommended standard are Iron (Fe) with a mean value of 1.25mg/l and the permissible limits for drinking and domestic use as 0.3mg/l. Also, aluminum (Al) has concentration value of 0.38mg/l while its permissible limit for drinking purpose is 0.2mg/l. Comparing the result of the XRF analysis with WHO (2011) and NSDQW(2007) recommended standards, it was observed that most of the heavy metals identified arebelow the permissible limits for drinking purpose, domestic use and discharges into a stream which implies that the Samaru stream is not very polluted and finally, an F-ratio test (ANOVA) between the compounds of heavy metals and the compounds of non-heavy metalswas conducted and the result gives a significance value of 0.036 to imply that there is a significant difference between the two at 0.05 level of significance. This indicates that there is a difference in the effects of the factors that contributes in dissolve sediments yield to the composition and distribution of the compounds in the sediments of Samaru stream.