Preprints
https://doi.org/10.5194/hess-2017-217
https://doi.org/10.5194/hess-2017-217

  06 Jun 2017

06 Jun 2017

Review status: this preprint was under review for the journal HESS but the revision was not accepted.

Water levels of the Mekong River Basin based on CryoSat-2 SAR data classification

Eva Boergens1, Karina Nielsen2, Ole B. Andersen2, Denise Dettmering1, and Florian Seitz1 Eva Boergens et al.
  • 1Deutsches Geodätisches Forschungsinstitut der Technischen Universität München, Arcisstr. 21, 80333 München
  • 2Div. of Geodesy, DTU Space, National Space Institute, Kgs. Lyngby, Denmark

Abstract. In this study we use CryoSat-2 SAR (Delay-Doppler Synthetic Aperture Radar) data over the Mekong River Basin to estimate water levels. Smaller inland waters can be observed with CryoSat-2 data with a higher accuracy compared to the classical radar altimeters due to the increased along track resolution of SAR and the smaller footprint. However, even with this SAR data the estimation of water levels over smaller (width less than 500 m) is still challenging as only very few consecutive observations over the water body are present. The usage of land-water-masks for target identification tends to fail as the river becomes smaller. Therefore, we developed a classification to divide the observations into water and land observations based solely on the observations.

The classification is done with an unsupervised classification algorithm, and it is based on features derived from the SAR and RIP (Range Integrated Power) waveforms. After the classification, classes representing water and land are identified. The measurements classified as water are used in a next step to estimate water levels for each crossing over the Mekong River. The resulting water levels are validated and compared to gauge data, Envisat data and CryoSat-2 water levels derived with a land-water mask. The CryoSat-2 classified water levels perform better than results based on the land-water-mask and Envisat. Especially, in the smaller upstream regions the improvements of the classification approach for CryoSat-2 are evident.

Eva Boergens et al.

 
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Status: closed
Status: closed
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Eva Boergens et al.

Eva Boergens et al.

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Short summary
The water levels of the Mekong River are observed with the SAR altimeter measurements of CryoSat-2. Even small rivers in the river system with a width of 50 m can be observed due to the higher resolution of the SAR measurements. To identify the rivers regardless of a land-water-mask we employ an unsupervised classification on features derived from the SAR measurements. The river water levels are validated and compared to gauge and Envisat data which shows the good performance of the SAR data.