Multi-decadal oscillations in the hydro-climate of the Okavango River system during the past and under a changing climate

► Multi-decadal oscillations in the Okavango River basin, southwestern Africa. ► Weak multi-decadal rainfall signal magnified by catchment processes. ► GCMs simulate multi-decadal oscillations in 20th century. ► Oscillations in 21st century similar in magnitude but superimposed on drying trend. ► Mu...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 2012-12, Vol.475, p.294-305
Main Authors: Wolski, P., Todd, M.C., Murray-Hudson, M.A., Tadross, M.
Format: Article
Language:English
Subjects:
Climate
Climate change
Climate variability
Deltas
Drying
Earth sciences
Earth, ocean, space
Exact sciences and technology
Freshwater
Hydrology
Hydrology. Hydrogeology
Multi-decadal
Oscillations
Rivers
Trends
Water resources management
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Summary:► Multi-decadal oscillations in the Okavango River basin, southwestern Africa. ► Weak multi-decadal rainfall signal magnified by catchment processes. ► GCMs simulate multi-decadal oscillations in 20th century. ► Oscillations in 21st century similar in magnitude but superimposed on drying trend. ► Multi-decadal oscillations affect climate change assessments and require alternative water management approaches. The focus of this paper is to understand the multi-decadal oscillatory component of variability in the Okavango River system, in southwestern Africa, and its potential evolution through the 21st century under climate change scenarios. Statistical analyses and hydrological modelling are used to show that the observed multi-decadal wet and dry phases in the Okavango River and Delta result from multi-decadal oscillations in rainfall, which are likely to be related to processes of internal variability in the climate system, rather than external natural or anthropogenic forcing. Analyses of changes in this aspect of variability under projected climate change scenarios are based on data from a multi-model ensemble of 19 General Circulation Models, which are used to drive hydrological models of the Okavango River and Delta. Projections for the 21st century indicate a progressive shift towards drier conditions attributed to the influence of increasing temperatures on water balance. It is, however, highly likely that multi-decadal oscillations, possibly of similar magnitude to that of 20th century, will be superimposed on the overall trend. These may periodically offset or amplify the mean drying trend. This effect should be accounted for in water and catchment management and climate change adaptation strategies.
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2012.10.018