Surface Water Availability Mapping and Estimating Spatiotemporal Changes by Using Google Earth Engine, Rift Valley Lakes Basin, Ethiopia
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Date
2024-05
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Addis Ababa University
Abstract
The surface water availability in Ethiopia is fluctuating spatiotemporally due to natural and anthropogenic stressors. Previously hydrological models were used to estimate surface water availability at small watershed levels. However, data complexity and processing make them unable to assess at a wider basin level and require high performance computing technology. Therefore, in this study, Google Earth Engine (GEE) platform for surface water availability mapping and spatiotemporal surface water change assessment was carried out using Landsat satellite data and global surface water data for the last 4 decades in the Rift Valley Lakes basin. The research also investigates the impact of natural factors such as rainfall and temperature, as well as human-induced factors including land use and land cover changes, on surface water dynamics. The findings revealed that a significant increase in seasonal surface water accounting for a total area of 10 km2, 48 km2, and 577 km2 for year intervals 1984–2000, 2000–2010, and 2010–2020, respectively. The lost surface water body shows an increment of 63 km2 for the second interval while decrementing of 60 km2 and 41 km2 for the rest of the intervals. Lastly, the permanent water shows an increase by 10 km2, 34 km2 for intervals 1984-2000 and 2010-2020, respectively while decreasing by 56 km2 for the year interval 2000-2010. The analysis of stressors revealed notable changes in rainfall and Land use land cover while the temperature shows steady distribution except for two sub-basins. The rainfall distribution shows a decrease in maximum rainfall by 103 mm, and the minimum rainfall by 8 mm for the first year interval. The increment for the next two intervals, by a maximum rainfall of 241 mm, and a minimum rainfall of 232 mm and 10 mm in the maximum, and minimum rainfall 57 mm, respectively. In addition, the Land use land cover shows the spread in the Farmland areas and urban areas and the fluctuation of forest cover extent as well the replacement of bare lands by other land cover classes. The study revealed that fluctuations in surface water availability are primarily caused by variations in rainfall patterns and changes in land use and land cover. Furthermore, the effectiveness of the Google Earth Engine (GEE) platform in visualizing and analyzing large-scale data was demonstrated, suggesting its applicability in different fields. However, to enhance future research, it is crucial to include additional field verification points and incorporate diverse data sources to improve the accuracy of the findings. These measures are essential for advancing understanding in the field and obtaining more reliable and comprehensive results.
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Surface Water Availability, Spatiotemporal Fluctuations, Natural Stressors