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Observing Rivers With Varying Spatial Scales
Ernesto Rodríguez1, Michael Durand2, Renato Prata de Moraes Frasson1,2
1Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA.
Water Resources Research
|October 12, 2020
Summary
The Surface Water and Ocean Topography (SWOT) mission uses remote sensing to estimate river discharge. River slope measurement dictates observable river dynamics, impacting discharge estimation accuracy.
Area of Science:
- Earth Science
- Hydrology
- Remote Sensing
Background:
- The Surface Water and Ocean Topography (SWOT) mission aims to estimate global river discharge using remote sensing.
- Remote sensing offers synoptic data but has lower accuracy than in situ measurements.
Purpose of the Study:
- Determine the scales for observing river dynamics with remote sensing, considering spatial sampling and measurement noise.
- Develop an equation for spatially averaged rivers using remote sensing-derived hydraulic quantities.
Main Methods:
- Utilized calibrated hydraulic models to analyze power spectra of momentum equation terms.
- Introduced reach-averaged Saint Venant equations incorporating a variability index.
- Derived an exact expression for the effective friction coefficient increase.
Main Results:
- River slope measurement defines the scale of observable river dynamics.
- The variability index, multiplying the friction coefficient, accounts for within-reach variability.
- The effective friction coefficient is proportional to riverbed elevation variance and inversely proportional to depth.
Conclusions:
- The derived reach-averaged Saint Venant equations enable discharge estimation from remote sensing data.
- The approximated variability index is most accurate for lognormal river parameter distributions.
- Findings have significant implications for SWOT mission data interpretation and discharge estimation.
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