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Swiss Federal Institute of Technology (Zurich) (2007)

Climate change affecting the Okavango Delta

Burg, Vanessa

Titre : Climate change affecting the Okavango Delta

Auteur : Burg, Vanessa

Etablissement de soutenance : Swiss Federal Institute of Technology (Zurich)

Grade : Master Theses 2007

Résumé
The vast Okavango Delta, Northern Botswana, with its outstanding wetland flora and fauna, is under potential threat from climate change and local development. This thesis presents the possible impacts of global climate change on both the hydrology and the vegetation of the Delta. The investigation was done over two future time spans (20502080 and 2070‐2100) using the IPCC emission scenario A2, and five different climate models (CCC, CCSR, CSIRO, GFDL and HadCM3). In addition, a development scenario was determined to get an idea of the extent of the effects of global climate change in comparison to those of local human interventions. Modifications of the hydrological characteristics were estimated by modifying the past time series of runoff, rainfall and potential evapotranspiration and running a hydrological model of the Okavango Delta using those inputs. Simulations of climate change predict a drying‐up of the Delta ; i.e. deeper groundwater levels and lower inundation frequencies. The impacts of global climate change are expected to be much more important than those of the regional developments. In any case, deforestation along the Okavango River leads to an augmentation of the inflow to the delta, mitigating the local effects of climate change. Vegetation will have to adapt to the new hydrologic conditions. In this thesis, the distribution of the vegetation cover was analysed on the basis of flooding frequency and mean depth to the groundwater level. It was found that almost each vegetation type had a distinct preferred groundwater depth of occurrence. The trend of the effects of future climatic change and development on the different vegetation types can be simulated with this single parameter. The area covered by vegetation types that require rather wet conditions is expected to decrease. As there are many not widely spread vegetation types, which cover wet areas of the Delta, the decrease of the groundwater level will lead to a depletion of biodiversity.

Mots clés : GLOBAL WARMING, CLIMATOLOGY, CLIMATIC FLUCTUATIONS, RAINFALL-RUNOFF RELATION, HYDROLOGY, MAXIMUM RUNOFF, FLOODS, FLOOD RUNOFF, DELTAIC ENVIRONMENT, SEDIMENTARY, ENVIRONMENT, RIVER MOUTHS, ESTUARIES, GEOMORPHOLOGY, SPECIES DIVERSITY, BIODIVERSITY, BIOLOGY, AFRICAN RIVER, BOTSWANA, SOUTHERN AFRICA. REPUBLIC OF BOTSWANA

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