An improved methodology to estimate river stage and discharge using Jason-2 satellite data

- An improved methodology is developed to retrieve water level using altimetry.
- New methodology has improved the results for the braided reaches.
- We have also compared our results with Hydroweb data product.
- River flow characteristics are estimated using satellite altimetry.

SummarySatellite altimetry over inland water bodies is a technique to estimate water level of rivers, lakes and reservoirs. In this study river flow characteristics such as water level and discharge is estimated using Jason-2, 20 Hz waveform data. An improved approach is adopted to retrieve the water level information over the braided reaches of the Brahmaputra river. The morphological dynamics of braided rivers often makes it difficult to retrieve water level accurately. In the proposed methodology, supplementary information from microwave and optical images of monsoon and non-monsoon seasons is used to establish the virtual stations over the main channel of the river. A nested approach is adopted to create dynamic virtual stations to address the frequent channel shifting phenomena over the braided reaches of the river. The results indicate that, there is high variation in backscattering coefficient, which ranges from mean value of 35 dB during the non-monsoon season to 48 dB during the monsoon season. It clearly highlights the seasonal variability of river flow in the Brahmaputra. The water level retrieval is done using Ice-1 retracking algorithm. The statistical analysis of retrieved water level have shown good agreement with in situ (observed) water levels when compared for Jason-2 satellite tracks 53, 166, 231 and 242 passing over the Brahmaputra river. The water level information is converted into discharge time series for the satellite 166 using the rating curve of Guwahati gauge station. The root mean square error of retrieved water levels is in the range of 50-55 cm. Water level retrieved using proposed methodology are compared with Hydroweb and DAHITI water level product. It was found that proposed methodology has enhanced the altimeter derived water level accuracy for the different reaches of the braided Brahmaputra river.