The Nile hydroclimatology : impact of the Sudd wetland

Hydroclimatology emerges as a new discipline because of the increasing recognition of the coupled nature of landsurfaceatmopshere processes. Land use change affects the atmospheric moisture conditions, not only locally but also at continental scales. Similarly climate change influences river basin hydrology and water resources. Good understanding of the atmospheric part of the regional water cycle is important for sound (integrated) water resources planning and management at river basin scale. The Nile Basin is characterized by increasing water demands in the downstream areas and large evaporation from the Upper Nile swamps (Sudd, Bahr el Ghazal, and Mashar marshes). This led to the planning and construction of river short cut channels to intercept the water feeding the wetlands (e.g. the uncompleted Jonglei canal). Despite the importance of the wetlands to the local environment, and as an expected supplier of additional Nile water, its hydrology and its interaction with the climate is not known precisely. How large is the wetland? How much does it evaporate? What is the impact on the regional hydroclimatology? These have been strongly debated issues over the last decades. This study aims at a better understanding of the Sudd hydrology in relation to the regional hydroclimatology, and to provide quantitative answers to the above questions. The impact of the Sudd wetland on the Nile hydroclimatology has been studied by comparing two regional climate model scenarios: the present climatology, and a drained Sudd scenario. Remote sensing techniques have been utilized intensively to derive evaporation and related biophysical properties over the wetlands. The derived results from this study (e.g., changes in microclimate, additional river flow, etc.) can also serve as boundary conditions for related impact assessment models (ecological, water resources planning, socio-economic, etc.