Temporal characterization of daily rainfall trends in Zambia from 1983 to 2019: a crop growing season perspective.

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Kapil, Liteta Biggie
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The University of Zambia
Daily rainfall amounts and distribution are known to be highly variable leading to either low crop yields or total crop failure in some parts of Zambia because many small scale farmers depend on it as a main source of moisture to support the growth of crops. Therefore, this study aims to provide improved knowledge and evidence on current (1983-2019) rainfall trends in Zambia using CHIRPS data with the aim of drawing inferences of their implications on the length of crop growing seasons. The study adopted an explanatory sequential embedded mixed method research design that allowed approaching the study problems from different perspectives. Stratified random sampling and purposive sampling methods were utilized to reach the saturation point. Objective one was analyzed with The Mann-Kendall (MK) test, a statistical non parametric test widely used for trend analysis in climatological and hydrological time series data. Mann-Kendall test is advantageous because it does not require the data to be normally distributed. The Standard Precipitation Index technique was employed in determining the characteristics of intra-annual rainfall variability. Furthermore, qualitative data analysis was performed by utilising a rainfall-based criterion which was earlier used by the Famine and Early Warning System (FEWS). Results show that the average rain season onset dates are 19th , 17th , and 16th of November for agro-ecological regions 1, 2, and 3 respectively. Further, with an average withdraw date of 19th March; agro-ecological region 3 experiences the latest cessation of the rainy season. Trends in rainy season length were found to be declining across all agro ecological regions with the steepest slope on the Sen’s estimator (-0.11) being observed over agro-ecological region 2, followed by region 1 (-0.08) and region 3 (-0.06) respectively. The observation that rainy seasons are getting shorter reflects the late onset that has been found across all agro-ecological regions. In conclusion, the observed decrease in the length of the rainy season translates into shorter crop growing seasons. This is likely to affect the choice of crops to be grown in each of the three agro-ecological regions. Therefore, the research recommends farmers in AER 3 potentially to have multiple harvests in any given season or could easily diversify. However, in the case of the Agro ecological Regions 1 and 2 early maturity crops and establishment of irrigation systems are possible solutions to the observed decrease in rainy season length.
Thesis of Masters of Science in Geography