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Universiteit Gent (2011)

Drought assessment in Zambia in the face of climate change

KALUBA Peter Kasolota

Titre : Drought assessment in Zambia in the face of climate change

Auteur : KALUBA Peter Kasolota

Université de soutenance : Universiteit Gent

Grade : Master of Science (MS) Physical Land Resources 2011

Over the past three decades, the frequent drought and flood have characterized most countries in southern Africa and Zambia is not an exception. Normal weather rarely occurs countrywide due to these extreme weather events. Droughts have had the biggest shock to the country’s food security since they are more frequent than floods. This has manifested in form of poor economic performance due to over reliance on rainfed agriculture reducing the chances of achieving the national development goal of strengthening agricultural and rural income. Thus drought assessment was carried out to find the magnitude and areal extent of droughts capable of affecting Zambia, since knowledge of their expected frequency for a variety of durations is imperative, if they are to be well managed. Based on monthly rainfall data from 34 widely distributed weather stations in Zambia, the Index Flood Regional Frequency Analysis based on L-moments (RFA-LM) was applied. Discordancy values as a first step were used in screening whether the site L-moments ratios were within range of the average L-moments of a group of similar stations forming a subregion. Homogeneous sub-regions were formed by grouping stations within a similar range of mean annual precipitation (MAP) and was validated by the heterogeneity test. Based on the criteria of the goodness-of-fit test statistics (Z|DIST| = ± 1.64), the Generalized Extreme Value (GEV) distribution was the best regional distribution. To produce maps, regional predictor equations for L-moment ratios and MAP were developed for the study area. Finally the spatial mapping of at-site means and regional statistical parameters were inputted in L-map to produce spatial maps of drought recurrences. Droughts of magnitude 20, 30 and 40% deficit of normal rainfall were found to correlate to return periods of previous droughts reported for the country. The 20% and the other two deficits were synonymous to moderate and severe drought, respectively. The higher the magnitude of drought, the lower was the return period. The RFA-LM analysis showed the return period of droughts to increase from south to north of Zambia. The area with the most frequent return periods of drought is the extreme south of Zambia (Sesheke and Livingstone) in the agroecological zone I. The narrow range and generally widely spread pattern in return periods in the Southern Province confirmed earlier studies why the province is the most susceptible to drought. Despite showing susceptibility to drought, the Southern and Eastern Province contribute substantially to food production, giving reason that more attention is required to soil management measures such as conservation farming.

Source : Pedon 23 - Physical Land Resources - Universiteit Gent

Page publiée le 31 décembre 2015, mise à jour le 24 janvier 2018