Temperature Variability and Trends in Nzoia River Basin, Kenya

Abstract

Nzoia River Basin is one of the regions that is highly vulnerable to climate change in Kenya. Many attempts have been made to identify and quantify the impact of climate change on socio-economic sectors and ecosystems using global studies resulting into recommendations on policy changes aimed at generating sustainable mitigation and adaptation strategies. This top-down approach by using global studies lacks the required local and regional climate change specificities to address the regional and local climate change challenges. Temperature is one of the most important components of the climatic parameters widely measured as a starting point towards the apprehension of climate change courses. This study aims at filling the top-down approach knowledge gaps in Nzoia River Basin by assessing temperature variability and trends at three stations for the period 1979 to 2014, using Linear regression analysis and Mann-Kendall statistical test. Monthly maximum and minimum temperature data for Kitale, Kakamega and Eldoret stations was obtained from Kenya Meteorological Department, Nairobi, Kenya. The main findings reveal that Kakamega has highest temperatures, followed by Kitale and the lowest temperatures are found at Eldoret. This trend seems to go with altitude as the lowest temperatures are found at highest altitudes and highest temperatures at lowest altitudes. There are significant increases in annual temperatures for Kitale and Kakamega stations, with Kitale showing annual maximum temprature rising at 0.0006260 C/year; annual minimum temperature rising at 0.0011630 C/year and the annual mean temprature rising at 0.0008940 C/year. Kakamega shows annual maximum temperature rising at 0.0007710 C/year; annual minimum temperatures rising at 0.0004710 C/year and the annual mean temperatures rising at 0.0006230 C/year. Eldoret shows falling maximum temperature at - 0.002020 C/year; rising minimum temperature at 0.0008130 C/year and falling mean temperatures at - 0.001420 C/year. The results for Kitale and Eldoret stations show statistically significant trends whereas those for Kakamega station were statistically insignificant. Eldoret annual minimum temperatures are rising faster than the maximum whereas in Kakamega it’s the annual maximum temperatures that are rising faster than the minimum. Kitale and Kakamega show annual mean temperatures rising at about 0.10C per century which compares well with IPCC Third Assessment Report estimated global warming rate of 0.6 0C during the twentieth century and other studies from the African continent and East African region.