1.5 Objectives of the thesis The overarching aim of the thesis was to understand the potential of water body detections by a wide-field-of-view sensor to indicate ecosystem status in West African drylands. An ecological indicator needs to be based on reliable input data. Thus, the first step was to assess the quality of the novel remote sensing derived water body dataset that is key to this research. The objectives were addressed with two research questions: (1) Are water body observations by wide-field-of-view satellite sensors reliable? Hypothesis: Water bodies can be reliably detected with an optical remote sensing time series at regional scale. Their maximum extent can be mapped and information about inter- and intra-annual seasonal changes can be identified based on the time series of water body detections. (2) What are the relationships between surface water, vegetation cover and rainfall at the ecosystem (or catchment) level and at the regional scale? Hypothesis: Relationships and interactions exist between the seasonality and extent of temporary water bodies, rainfall and vegetation cover. Changes in one factor lead to changes in one or more of the other factors. These changes can be quantified, localized and the relative contribution of each factor can be evaluated. A positive answer to the second hypothesis would imply that the spatial and temporal behaviour of temporary water bodies is a reliable ecological indicator for the state of an arid and semi-arid ecosystem. Thus, it will be possible to generate additional information on drought condition, fire risk, disease risk, land degradation risk, climate change, and biomass production (grazing potential) based on regional scale time series of remote sensing derived temporary water body maps. Actually, if the first hypothesis is supported, temporary water bodies would be relatively easy to monitor and more directly observable in real-time than the other factors mentioned.

HAAS Eva Maria; 

2010-12-21

Université catholique de Louvain

JRC56215

https://publications.jrc.ec.europa.eu/repository/handle/JRC56215,