SEDIMENT DELIVERY INTO THE KUBANNI RESERVOIR, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA

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Date
2013-01
Authors
YUSUF, Yakubu Obadaki
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Abstract
In an attempt to assess the sediment delivery into the Kubanni reservoir, a continuous monitoring of the four tributaries contributing sediments into the Kubanni reservoir, Ahmadu Bello University, Zaria from 2011 to 2012 was carried out. The monitoring was done by measuring their discharges using the 1200 and 900 v-notch weirs for the Malmo and Tukurwa streams and the velocity-cross-sectional area method for Maigamo and Goruba streams. Water samples were collected for onward analysis in the laboratory to derive the suspended and dissolved sediment concentrations. Products of the sediment concentrations and discharges gave the sediment loads and a rating relation between sediment loads and discharges was used to determine the sediment yield of the contributory tributaries. A February 2009 NIGERIASAT imagery was used for the classification and characterization of the Land use/Land cover of each sub-basin by supervised classification with maximum likelihood algorithm taking advantage of spectral signatures using ILWIS 3.7 software. The summary statistics including the channel suspended sediment yields of the four tributaries is increasing progressively with the Malmo stream having the least (248.29 tons/yr) and the Goruba stream having the highest (12880.55 tons/yr). The situation is not much dissimilar in the derived dissolved loads where the Malmo stream has the least value of 89.99 tons/yr and the Goruba stream has the highest value of 8654.77 tons/yr. The research revealed that the suspended sediment yield of the Malmo tributary has reduced almost by half tribute to the efforts of the University administration in their afforestation and reduction of farming activities within the sub-basin. There is a - 8 - significant difference between the suspended sediment yields of the four tributaries. There is also a significant difference between their respective dissolved sediment yields and comparing the suspended and dissolved loads of each of the tributaries also revealed a significant difference except for the Goruba stream. It was concluded that there exists significant relationship between land use and sediment yields of the tributaries with the scattered cultivation, apart from increasing progressively, making up the significant part of the LULC subsets for each of the sub-basins. The implication of this is that apart from the Malmo sub-basin, farming is prevalent, and is therefore the major contributor to their sediment yields. This signifies the overwhelming importance of LULC in determining sediment yield of rivers as inferred by previous works. This conclusion is further corroborated with the anomaly observed in the Maigamo sub-basin having the highest Specific Sediment Yield (SSY) as a result of man’s influence farming very close to its gauging station thereby affecting the consecutive increase in the SSY of the sub-basins. Based on the findings, recommendations were made to the Ahmadu Bello University administration among which are enforcement of the ban on farming, grazing and mining strengthened with a legal backing, acquisition of more lands, encouraging annual tree planting, building low check-dams, mounting sediment traps at strategic locations, long term monitoring of the tributaries and dredging of the reservoir.
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A DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA IN PARTIAL FULFILMENT FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN GEOGRAPHY. DEPARTMENT OF GEOGRAPHY AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
SEDIMENT, DELIVERY, KUBANNI, RESERVOIR, AHMADU, BELLO, UNIVERSITY, ZARIA, NIGERIA
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