On using water surface slope for estimating discharge in critical backwater conditions: case study of the Poyang lake, China.
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science IV: 25 years of satellite altimetry for Cryosphere and Hydrology: from experimental to emerging operational applications
Presentation type: Type Poster
In this study, we estimated the discharge at the Poyang Lake mouth using Manning-based formulations of the stage-discharge-slope relationship and both in-situ and satellite datasets. The results show that a classical two-variable (H-Q) power equation is not able to reproduce properly the temporal variations of the discharge. Conversely, use of the daily WSS (Water Surface Slope) estimated from gauge stages as a third parameter in the formulation improved dramatically the fit between observed and estimated discharges. We used 3 Virtual Stations (VSs) from past Nadir altimetry missions (ENVISAT and SARAL) to estimate the WSS at the mouth of the Poyang Lake on a monthly time step. The WSS taken from satellite altimetry also improved the discharges estimates at the Poyang Lake’s mouth.
This result illustrates the importance of using the surface slope together with stages and discharges to build a reliable rating curve –hence predict discharge- in such a critical backwater situation. The future SWOT mission will provide an improved (both in frequency and precision) estimate of the WSS. Our capability to estimate discharge in such complex contexts should benefit largely of these new observations.