Abstract
Water scarcity is one of the main challenges posed by the changing climate. Especially in semi-arid regions where water reservoirs are filled during the very short rainy season, but have to store enough water for the extremely long dry season, the intelligent handling of water resources is vital. This study focusses on Lac Bam in Burkina Faso, which is the largest natural lake of the country and of high importance for the local inhabitants for irrigated farming, animal watering, and extraction of water for drinking and sanitation. With respect to the competition for water resources an independent area-wide monitoring system is essential for the acceptance of any decision maker. The following contribution introduces a weather and illumination independent monitoring system for the automated wetland delineation with a high temporal (about two weeks) and a high spatial sampling (about five meters). The similarities of the multispectral and multi-polarized SAR acquisitions by RADARSAT-2 and TerraSAR-X are studied as well as the differences. The results indicate that even basic approaches without pre-classification time series analysis or post-classification filtering are already enough to establish a monitoring system of prime importance for a whole region.
Highlights
It is well known that the global warming predicted for the coming decades goes along with an increasing severity of weather phenomena
Though this allows a near-real time measurement of the water level at a certain point, and modelled water volumes, it provides no reliable information about the remaining water resource, for wetlands like Lac Bam where siltation rates are so high that the lake floor topography is constantly changing (Moser et al, 2016)
The turbid and sediment-rich water bodies show very high reflectance values in the visual part of the spectrum, similar to bare soil, and much higher than usual reflectance in the near infrared part, which is favoured for water detection because almost all the radiation is absorbed, resulting in very low values over surface water
Summary
It is well known that the global warming predicted for the coming decades goes along with an increasing severity of weather phenomena. The current standard is the installation of water gauges at selected locations, e.g. dams Though this allows a near-real time measurement of the water level at a certain point, and modelled water volumes, it provides no reliable information about the remaining water resource, for wetlands like Lac Bam where siltation rates are so high that the lake floor topography is constantly changing (Moser et al, 2016). Optical remote sensors share three main problems: First, they require cloud-free conditions and sufficient sun illumination They only report the reflectance directly on the illuminated surface, i.e., water covered by plants will be detected as green canopy (vegetation). The turbid and sediment-rich water bodies show very high reflectance values in the visual part of the spectrum, similar to bare soil, and much higher than usual reflectance in the near infrared part, which is favoured for water detection because almost all the radiation is absorbed, resulting in very low values over surface water
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