Long-Term Monitoring of Lakes and Wetlands With Satellite Data and GIS.

There is a need for simple and cost/effective techniques to monitor the long-term changes of wetlands and lakes over large or remote regions. Because of its synoptic capacity and numerous archives remote sensing offers an appropriate means for this purpose. However, through the examples of large regions of Central Africa and South East Australia, it is shown that some difficulties still need to be overcome. In the Lake Chad basin, Central Africa, large water bodies are characterised by extremely variable extents and often covered by fast growing vegetation. In the Glenelg and Hopkins basins, numerous small wetlands can easily be confused with irrigated areas. This poster presents how a combination of remotely sensed data from passive sensors (vegetation index, thermal and near-infrared data) together with information from GIS (digital elevation model, drainage network) offers a suitable system for the long-term monitoring of wetlands and lakes extent. It also highlights that the thermal band conveys crucial information and has too often been neglected. For the two regions, this methodology enables to analyse in detail and over several decades the changes that have affected the wetlands and lakes.