Discharge estimates with stage-fall-discharge rating curves and ICESat-2
altimetry at backwater-affected virtual stations
Satellite altimetry has become an important data source for discharge
estimation. Stage-fall-discharge (SFQ) rating curves are necessary for
discharge estimation at backwater-affected river reaches because of
non-uniqueness of stage-discharge (SQ) relationships. We used a
hydrodynamic model to simulate stage, water surface fall, and discharge
at six backwater-affected reaches and generated SQ/SFQ rating curves
everywhere along the river. The simulated SQ rating curves showed that
the uncertainties of the estimated discharge were on the order of 150%.
The uncertainties were reduced to less than 35% when using SFQ rating
curves in rivers with significant falls. We used ICESat-2 laser
altimetry, which synchronously measures stage and fall, to estimate
discharge with the simulated SFQ rating curves in the Missouri River.
The study highlights the importance of backwater effects for discharge
estimation, particularly for VS located upstream of major tributary
junctions, and showcases the possibilities of ICESat-2 laser altimetry
for EO-based discharge estimation.