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Examining trends of hydro-meteorological extremes in the Shire River Basin in Malawi

Journal Contribution - Journal Article

© 2019 Elsevier Ltd Malawi experiences frequent floods and droughts and these hydrological extremes kill and displace people and damage infrastructure. In recent years, the trend of these extreme events has increased in frequency and magnitude and has threatened socio-economic development of the country. Analysis of trends and frequency of hydro-meteorological extremes that cause floods and droughts is very vital in understanding the hydrological systems and this may assist in averting disasters associated with those extremes. For extremes extracted from long-term hydro-meteorological records, a significant trend may indicate a shift from the natural changes to the changes induced by human activities on one hand and on the other hand, decadal or multi-decadal oscillations in the occurrence of hydro-meteorological extremes may demonstrate the influence of the (multi-) decadal persistence of the climate system. In Malawi, studies on trends of hydro-meteorological extremes of rainfall, temperature and streamflows are scanty as most studies have focused on the means. This study, therefore, aimed at examining trends and frequency of these hydro-meteorological extremes in the Shire River Basin in Malawi. Daily scale data from 1961 to between 2005 and 2015 were collected from 22 rainfall stations, 12 temperature stations and 10 river discharge station within the study area. The hydro-meteorological extremes were analyzed using annual maximas and annual minimas of the daily hydro-meteorological data. Significance and direction of trends in these extreme indices were examined using the non-parametric Mann–Kendall test statistic. The Peak-Over-Threshold (POT) approach, applying the Generalized Pareto Distribution (GPD) was used to analyze the distribution of the extremes. Study results have shown that temperature extremes have an increasing trend which is significant at 5% significance level. In terms of streamflows, both the peak and low flow extremes have shown a decreasing trend, which is consistent with the decreasing trends observed in rainfall extremes. Analysis of frequency of extreme events has shown that extremely high rainfall events have a high probability of occurrence while streamflow extremes will not occur frequently. These findings have provided key insights that are key in understanding the temporal occurrence of hydro-meteorological extremes in the basin, which are of benefit to the regional water resources planning and development.
Journal: Physics and Chemistry of the Earth
ISSN: 1474-7065
Volume: 112
Pages: 91 - 102
Number of pages: 12
Publication year:2019
Keywords:Environmental science & technology, Geosciences & technology, Meteorology/atmospheric & aerospace science & technology