[01] Kenny Nyirenda, Department of Geology and Survey, Copperbelt University, Kitwe, Zambia. [02] Emmanuel Sachikumba, Zambia Forestry College, Mwekera, Kitwe, Zambia.

Extreme events are the major cause of droughts, floods and other associated disasters worldwide. Therefore, understanding trends in extreme rainfall events is important in mitigating their impacts on socioeconomic sectors such as health, agriculture, water resources and the environment. Against this background, a study was undertaken to investigate trends in extreme rainfall events in Kasama, Lusaka and Livingstone (representing agro-ecological regions 1, 2 and 3 of Zambia respectively) and their potential implications on water resources and agriculture. Gridded daily precipitation data from National Oceanic Atmosphere Administration (NOAA) with the spatial coverage of 0.50 - degree latitude x 0.50 - degree longitude grid (720x360) and temporal coverage from 1979 to 2017 were used. Eleven extreme precipitation indices were generated from NOAA precipitation data using the RClimDex package in R software. The data was processed by checking the homogeneity, while the trend for each extreme rainfall index was calculated using the Mann-Kendall, a non-parametric test. Results of the study revealed statistically significant decreasing trends in annual total precipitation, Simple Daily Index (SDII), heavy rainfall (R95P, R99P and RX1DAY) and the persistence of intense rainfall events (R10mm, R20mm and R25mm) in Kasama area. Decreasing trends in total annual precipitation and the persistence of intense rainfall events were also observed in Lusaka and Livingstone although were insignificant at 5% significance level. In Lusaka town, statistically significant trends in consecutive dry days (CDD) and consecutive wet days (CWD) were observed. The trend in CDD increases at the rate of 1.3days per year while that for CWD decreases at 0.17days per year. Decreasing trends in CDD and CWD were also observed in Kasama and Livingstone area although not statistically significant at 5% significant level. These trends point to the change towards drier conditions especially in Lusaka area. This coupled with the decrease in total annual rainfall may in the long run impact negatively on groundwater recharge, soil moisture content and surface water resources, and subsequently agricultural productivity especially rain fed agriculture. Improved natural resources management in Zambia especially water resources will be critical in mitigating the aforementioned potential impacts of extreme precipitation events.

Extreme Rainfall, Climate, Water Resources, Agriculture

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