A new method to derive river discharge from satellite altimetry (ENVISAT)

The publicly available global discharge database has been on the decline, lately. In the recent past, satellite altimetry has been investigated as an alternative for monitoring inland water level. In the present study, altimetry footprints in the vicinity of river gauging stations are analyzed for a functional relationship between the water level measurements from altimetry and discharge from the gauging stations. The functional relationship is generally established via a rating curve computed using simultaneous data. This study proposes a new method to infer this functional relation without the need for having synchronous datasets. RMS errors of 0.9-4.3 mm/month for estimated runoff of the rivers under study have been verified by the validation of estimated discharge against the in situ measurements. Further, in order to reduce the noise and cope with the problem of gaps in the estimation, a Kalman filter is used to achieve an unbiased discharge with minimum variance.