IGCP 565 Project Workshops

IGCP 565 Workshop 4: Integration of geodetic observations and products in models of the hydrological cycle Support for water management through hydrological models and data assimilation November 21-22, 2011 Johannesburg, South Africa

Climatic, hydrological and geomorphological changes in the Okavango Delta

Piotr Wolski
Okavango Research Institute, University of Botswana 

The Okavango Delta is a large, pristine flood-pulsed wetland system located in northern Botswana. Flooding in the Okavango Delta is characterized by variability manifested at a range of temporal scales, from seasonal to multidecadal, with the latter having the dominant influence on the characteristics of the Okavango wetland ecosystems. Additionally, endogenous factors such as geomorphological and tectonic processes and vegetation-hydrology feedbacks contribute to climate-independent transformation of the hydro-ecological system. Results of recent studies are presented that seek to explain the observed hydrological variability in the Okavango Delta in the context of interactions between natural climatic variability, anthropogenic climate change, and endogenous transformation of the wetland. Statistical analyses and hydrological modelling are used to show that multidecadal periodicity in the Okavango Delta results from weak multidecadal periodicity in rainfall, possibly related to global climatic processes represented by the Pacific Decadal Oscillation. GCM-based attribution study indicates that anthropogenic climate change likely moderates the high flood conditions in the Okavango Delta observed in the recent years. A probabilistic model of inundation, based on a time series of satellite images-derived inundation maps, indicates that the entire system is subject to gradual redistribution of water, possibly tectonically-driven. Further research in the context of AfricaArray project is discussed.