Environmental impact of rainfall variability In semi-arid areas: a case study of Baringo District, Kenya

Abstract

Studies in climatology have revealed that the weather patterns of the world have become very variable during the last half of the twentieth century. The causes of the variability have identified as sunspot activity, earth's orbit, decline in the solar beam, injection of both natural and man made aerosols in the atmosphere, depletion of the ozone layer and albedo change due to deforestation and increased carbon dioxide in the atmosphere. The most affected weather element by the above mentioned factors is rainfall and the .areas most affected by the sudden changes in rainfall characteristics are the Arid and Semi-arid Lands (ASAL) of the world, which are already moisture constrained. Most parts of Africa suffer from aridity, where for example, 83 percent of Kenya's total area is either arid or semi-arid. . The study generally focussed on the impact of rainfall variability on environmental transformations in semi-arid Baringo district in Kenya. Other objectives include: Identification of rainfall characteristics i.e intensities droughts and trends between 1960- 1995 by use of monthly and annual rainfall totals, identification of the impact of rainfall variability impact on pastoralism, crop cultivation and the general economic status of the people of semi-arid Baringo. In order to achieve the stated objectives, the following hypotheses were selected for testing:- There is no significant difference in rainfall variability between Marigat and Nginyang, there is no significant relationship between rainfall variability and (a) size (b) depth and (c) fish production on lake Baringo and there is no significant relationship between rainfall variability and (a) animal loss (b) crop production in semi-arid Baringo. Methods of data collection in this study include:- Reviewing of the available literature related to the topic, collection of relevant documented data from weather stations, KEMRI, Fisheries department, Ministry of Agriculture and Livestock development, all located within the study area, and Administration of structured and unstructured questions on selected topics (pastoralism, crop cultivation, health). Techniques in climatology such as precipitation Concentration Index (PCK), Coefficient of Variability (CV), Relative Variability (RV) Correlation Coefficient, Student t-test and Time Series analysis were used. Empirical findings established that semi-arid Baringo suffers from erratic and variable rainfall in time and space, such that, there was a significant difference in rainfall between, Marigat and Nginyang where Nginyang was best described as arid while Marigat as semi-arid. It was further established that Marigat experienced frequent droughts lasting between 2-3 consecutive years, while Nginyang experienced prolonged droughts lasting over five consecutive years leading to temporary climate change. The general rainfall trend in the study area pointed towards drier conditions in future. The study also established a strong correlation between rainfall variability, lake Baringo size and depth such that, when rainfall increases the size(surface area) and depth of the lake increases and during droughts, the lake shrinks in size and drops in depth. Surprisingly, there is minimal correlation between rainfall variability and fish production. Rainfall amount has very little influence on fish production. On the other hand, it was established that rainfall variability was responsible for a great percentage of animal loss collapse of rainfall rainfed crop cultivation in Marigat, poor health and school enrolment and attendance. From the findings of the study, was concluded that rainfall variability in semi-arid Baringo was responsible for the economic collapse, poverty and persistent starvation among the residents. In order to alleviate some of the problems caused by rainfall variability in the study area, a holistic approach was recommended where all the relevant personnel must work together towards behavioural change of the residents, technical and scientific improvement of the environment.