Trend Analysis of Hydro-meteorological Data for River Kaduna at Shiroro Dam Site, Niger State Nigeria

Abstract

Variation in the hydro-climatic variables of River Kaduna at Shiroro Dam site, Nigeria is linked to a number of climate change activities around the river. In view of this, the paper aims at examining the trend of stream flow, rainfall, temperature and evaporation. Monthly discharge, rainfall, temperature and evaporation records were obtained for a period of Thirty Three (33) years (1980-2012). These variables were used to examine the trend of the area. Incremental/Reductional analysis was used to determine a positive and negative change with percentage hydro-climatic variables difference. Mann- Kendall test, Turning point test and Kendall’s Rank Correlation were also used to estimate the significance of the trend. The result of the Mann –Kendall shows that the month of September had a value of Zs equals -2.09 (greater than Z_0.025) which makes it statistically significant; the rainfall value has no trend on a long term basis; the month of February and October had values of Zs equal to -2.2 (greater than Z_0.025) which made it statistically significant; the month of October had a value of Zs equal to 2.2 (greater than Z_0.025 ) which makes it statistically significant. Turning Point and Kendall’s Rank correlation Tests indicated that the variables have negative trends. The incremental/reduction analysis indicated that the discharge, rainfall and evaporation have significant trend (10 %, 90 % and 35 %) on the seasonal than the long term basis while the trend of temperature was significant on long term than the seasonal which has little or no trend (0.37%) in the area. The study shows that the trend pattern of stream flow, rainfall, temperature and evaporation from 2002 - 2012 was extremely high compared to 1980 - 1990 and 1991 – 2001. It is thus recommended that River Kaduna should be dredged and channelised so as to reduce depth of runoff during the full wet seasons. Also, deforestation and bush burning activities around the river at Shiroro Dam site should be prohibited.