Combining multisource satellite data to estimate storage variation of a lake in the Rift Valley Basin, Ethiopia

https://doi.org/10.1016/j.jag.2020.102095Get rights and content
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Highlights

  • Worldwide many lakes are dramatically dwindling or completely drying up.

  • Novel lake monitoring approaches with alternative data sources to overcome the limitations of in-situ data is essential.

  • Integrating satellite imagery and radar altimetry is viable for frequent and accurate lake monitoring and change detection.

  • Since 2009 Lake Ziway in Ethiopia has lost 12.75 % of its water storage volume.

Abstract

Integration of remote sensing data sets from multiple satellites is tested to simulate water storage variation of Lake Ziway, Ethiopia for the period 2009-2018. Sixty Landsat ETM+/OLI images served to trace temporal variation of lake surface area using a water extraction index. Time series of lake levels were acquired from two altimetry databases that were validated by in-situ lake level measurements. Coinciding pairs of optical satellite based lake surface area and radar altimetry based lake levels were related through regression and served for simulating lake storage variation. Indices for extracting lake surface area from images showed 91–99 % overall accuracy. Lake water levels from the altimetry products well agreed to in-situ lake level measurements with R2 = 0.92 and root mean square error of 11.9 cm. Based on this study we conclude that integrating satellite imagery and radar altimetry is a viable approach for frequent and accurate monitoring of lake water volume variation and for long-term change detection. Findings indicate water level reduction (4 cm/annum), surface area shrinkage (0.08km2/annum) and water storage loss (20.4Mm3/annum) of Lake Ziway (2009–2018).

Keywords

Landsat lake surface estimation
Lake level radar altimetry
Water volume variation
Change monitoring
Lake Ziway

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