Stochastic Variability of Rainfall and its Impact on the Flooding Regime of the Zambezi Flood Plain

Joseph T. Mwale, Idani Lichilo, Racheal Luneta

This research assesses the impact of rainfall variability on the flooding regime of the Zambezi floodplain as part of the scientific endeavour to understand the dynamics of hydrologic variability in natural systems such as riverine and floodplain ecosystems. In the context of global environmental change, hydro-climatic fluctuations are observed to be intensifying in magnitude and frequency with notable impacts on both human and natural systems. Understanding variability is important for the effective management of ecosystems which sustain human livelihoods. The study was conducted on a temporal scale of 50 years from 1965 to 2014 based on observed discharges and rainfall at the Chavuma National Gauge Station in the Zambezi district of Zambia. The research was guided by the hypothesis that there were no significant variations in the discharge on account of rainfall variability. Statistical methods of data analysis employed included exploratory, frequency and sensitivity analysis techniques. The results of the analysis revealed significant inter-annual variation of 21% in the discharge time series with a dominant periodicity of 10 years in its sinusoidal discharge signal. The sensitivity of the discharge to rainfall was found to be insignificant with a very low precipitation elasticity of streamflow of 0.03. In view of these findings, the conclusion of the study is that the flooding regime of the Zambezi floodplain is seemingly robust against the variability of rainfall. However, further research needs to be undertaken to provide deeper insight into the changes in the flooding regime of the Zambezi floodplain taking into account a broader spectrum of natural and anthropogenic forcing, and to quantify the flooding regime for integrated wetland management linking the dynamics of flooding to the biological diversity in the ecosystem.

https://doi.org/10.31871/WJRR.3.5.34