Monitoring water level variation in mekong river by satellite altimetry and remote sensing approaches

Water level (WL) and water volume (WV) are indicators of water resource allocation, climate change, and hydrology study. However, it's difficult to obtain in-situ data for remote regions, because it required deployment of infrastructure and regular maintenance. Therefore, satellite altimetry is a potential solution for WL retrieval. Although new generation of altimetry satellites has improved the inland water level accuracy, the resolution still limited by fixed/distant groundtracks and long revisit period. Furthermore, some of the measurements are subject to terrain disturbance. Therefore, we proposed an alternative approach that combined satellite altimetry, remote sensing (RS) images and Digital Elevation Model (DEM) to monitor WL and WV variation. The altimetry data was obtained from Envisat radar altimetry satellite, while RS images were acquired by Landsat-5/-7. We extracted water area (WA) from images by using the Modified Normalized Difference Water Index (MNDWI), combined with altimetry WL measurements and DEM to create WL-WA and WA-WV relational function. Then, the WL could be approximated from optical satellite images, and WV can also obtained from altimetry measurements. We applied this method in Jinghong Dam, one of the dams located in upper Mekong River. The result showed that RS-approach matched pretty well with local information and altimetry data. We further compared the result with local information. The comparison showed that estimated WV matched the storage of Jinghong Dam. In the future, we will test this approach with other study areas, and further combine Tropical Rainfall Measuring Mission (TRMM) data to remove the rainfall effect. Then, we can analyze the impact caused by dam construction.