Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Attribution of Floods in the Okavango Basin, Southern Africa

TitleAttribution of Floods in the Okavango Basin, Southern Africa
Publication TypeJournal Article
Year of Publication2014
AuthorsWolski, Piotr, Stone Daithi A., Tadross Mark, Wehner Michael, and Hewitson Bruce
JournalJournal of Hydrology
Volume511
Pages350-358
Abstract / Summary

In the charismatic wetlands of the Okavango Delta, Botswana, the annual floods of 2009–2011 reached magnitudes last seen 20–30 years ago, considerably affecting life of local populations and the economically important tourism industry. In this study, we analyse results from an attribution modelling system designed to examine how anthropogenic greenhouse gas emissions have contributed to weather and flood risk in our current climate. The system is based on comparison of real world climate and hydrological simulations with parallel counterfactual simulations of the climate and hydrological responses under conditions that might have been had human activities not emitted greenhouse gases. The analyses allow us to address the question of whether anthropogenic climate change contributed to increasing the risk of these high flood events in the Okavango system.

Results show that the probability of occurrence of high floods during 2009–2011 in the current climate is likely lower than it would have been in a climate without anthropogenic greenhouse gases. This result is robust across the two climate models and various data processing procedures, although the exact figures for the associated decrease in risk differ. Results also differ between the three years examined, indicating that the “time-slice” method used here needs to be applied to multiple years in order to accurately estimate the contribution of emissions to current risk. Simple sensitivity analyses indicate that the reduction in flood risk is attributed to higher temperatures (and thus evaporation) in the current world, with little difference in the analysed domain’s rainfall simulated in the two scenarios.

URLhttps://doi.org/10.1016/j.jhydrol.2014.01.055
DOI10.1016/j.jhydrol.2014.01.055
Journal: Journal of Hydrology
Year of Publication: 2014
Volume: 511
Pages: 350-358
Publication Date: 04/2014

In the charismatic wetlands of the Okavango Delta, Botswana, the annual floods of 2009–2011 reached magnitudes last seen 20–30 years ago, considerably affecting life of local populations and the economically important tourism industry. In this study, we analyse results from an attribution modelling system designed to examine how anthropogenic greenhouse gas emissions have contributed to weather and flood risk in our current climate. The system is based on comparison of real world climate and hydrological simulations with parallel counterfactual simulations of the climate and hydrological responses under conditions that might have been had human activities not emitted greenhouse gases. The analyses allow us to address the question of whether anthropogenic climate change contributed to increasing the risk of these high flood events in the Okavango system.

Results show that the probability of occurrence of high floods during 2009–2011 in the current climate is likely lower than it would have been in a climate without anthropogenic greenhouse gases. This result is robust across the two climate models and various data processing procedures, although the exact figures for the associated decrease in risk differ. Results also differ between the three years examined, indicating that the “time-slice” method used here needs to be applied to multiple years in order to accurately estimate the contribution of emissions to current risk. Simple sensitivity analyses indicate that the reduction in flood risk is attributed to higher temperatures (and thus evaporation) in the current world, with little difference in the analysed domain’s rainfall simulated in the two scenarios.

DOI: 10.1016/j.jhydrol.2014.01.055
Citation:
Wolski, P, DA Stone, M Tadross, M Wehner, and B Hewitson.  2014.  "Attribution of Floods in the Okavango Basin, Southern Africa."  Journal of Hydrology 511: 350-358.  https://doi.org/10.1016/j.jhydrol.2014.01.055.