THE EFFECT OF DRAINAGE BASIN MANAGEMENT ON SEDIMENT DELIVERY BY THE MALMO STREAM, KUBANNI DRAINAGE BASIN, ZARIA, NIGERIA.

Yusuf, Y. O.

The Ahmadu Bello University (ABU) dam receives water and sediments from the upstream catchment area of River Kubanni, which is made up of four tributaries. An earlier assessment of the magnitude of sediment produced by the northernmost tributary of the river was made for one year with data on sediment concentration and stream discharge collected from the gauging station made up of a 120o V-notch weir and a stage used to estimate the discharges. Suspended sediment samples were collected using the USDH 48 sampler for onward analysis in the laboratory to determine the suspended sediment concentration. The rating curve was used to allow a reasonable estimate of suspended sediment yield. A Channel Sediment Yield (CSY) value of 482 tons/yr was derived for the catchment area. This value is high and the information thus provided presents the need for immediate measures to control sediment yield into the ABU reservoir. Owing to the continuous effort of the ABU administration in afforestation with yearly tree planting campaign and reduction of farming activities, the author carried out the same study five years after to observe if there is a significant reduction in the sediment yield of the sub-basin and derived a CSY value of 248 tons/yr indicating a reduction of about 50% which can be said to be statistically significant thus making the efforts of the administration positive and commendable.

Key words: Discharge, Suspended Sediment Concentration, Suspended Sediment Discharge and Channel Sediment Yield.