CLIMATE VARIABILITY AND ITS IMPACT ON WATER RESOURCES OF LOWER KADUNA RIVER CATCHMENT NIGERIA

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Department of Engineering

ABSTRACT
Climate Variability in Study Area, located between latitude 10° 15’ and 10° 45’ North and longitude 6° 15’ and 7° 45’ East with an area of 1647 square kilometers in Kaduna State and within the Northern Guinea Savannah Climatic/Ecological zone and its Impacts on Water Resources of the Area were investigated in this report using 47years (1960-2006) record of hydro-meteorological data. The Climate variability was evaluated using a simple approach which considered variability as the difference between the means and standard deviations of climatic elements of two equal -length time periods. Other methods used include coefficient of variation, time series methods and anomaly approach. The impacts of climate variability on water resources of the study area were investigated using comparative and correlation analyses. From the results, the hottest year within the zone was 1993 with day time temperature increase of 15.3? and a zonal average of 0.08?, indicating warming while within the catchment, the highest increase in maximum temperature was 2.6?. The maximum increase in the minimum temperature was 8.2? in 1998 within the zone but 9.2? in the catchment area in 1979.The increase in the annual minimum temperature over the zone averaged 0.26?, indicating warmer nights. The historical observations of temperatures, rainfall and evaporation in the study area indicated annual maximum temperature trend of 0.12?, annual minimum temperature trend of 0.88? ,annual mean temperature trend of 0.48?, annual rainfall trend of 100mm and annual evaporation trend of 99mm which are all statistically significant except for the annual maximum temperature. Based on the coefficient of variation, the variations in the climatic elements ranged from low to moderate. The trend analyses of the discharges for the period, 1960 – 2006, showed that the annual total discharge, the annual maximum discharge and mean discharge have increased significantly during the past 47 years, whereas, the annual minimum discharge during the same period indicated a decline, which is not statistically significant.. From the anomaly analyses of the discharges and rainfall data in the study area, the increased annual rainfall relative to the 1961-1990 mean values between 1998 and 2003 coincided with the high annual discharges of Kaduna River within the same period respectively, which generated excessive surface runoff in River Kaduna system in recent years. This is in addition to the effects of urbanization due to population increase. These periods of excessive rainfalls and discharges, also, coincided with the periods of increases in the annual minimum temperatures, indicating positive impacts. The implication of this is that the tendency for flood events is increased. The declining minimum discharge increases water supply demand for domestic, industrial and agricultural uses especially, during dry season. The presence of positive significant trends in the historic temperature, rainfall and discharges indicate that the hydrologic changes, especially the recent incidences of flood events, in the study area and Kaduna River system may be attributed to Climate Variability. A Programme of monitoring of the Kaduna River system and forecasting should be established so that mitigation action can be planned ahead.