Versions Compared

Old Version 3

changes.mady.by.user Frederika Mourot

Saved on

compared with

New Version Current

changes.mady.by.user Frederika Mourot

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

🛰 Satellite(s)

ENVISAT, Jason-2 and -3, Sentinel-3A, CryoSat-2, and AltiKa. Landsat-8.

📊 Monitoring element

Water surface height and water slope.

🧰 Description technique

Zakharova et al. (2020) use a water mask defined from Level 1 Landsat 8 images using a Modified Normalized Difference Water Index.

They combine two methods to estimate discharge from altimetric measurements: the rating curve and the Manning methods.

📏 Accuracy / Resolution

  • Accuracy of the water height estimated combining CryoSat-2, AltiKa, and Sentinel-3A altimeters: 0.49 m for the Ob River (~2 km in width).

  • The accuracy of altimetric daily Q discharge estimates is 5–10% for the largest rivers (annual flow > 1000 km31000km3), ; 10–25% for large rivers (annual flow of 200–1000 km3km3); and 30–40% for medium size rivers (annual flow of 25–100 km325–100km3).

🗺 Case study

Two Arctic rivers (the Ob and Pur), western Siberia.

Tip

Benefits

The method provides higher discharge accuracy than previous studies relying on satellite measurements, on numerical modelling or on their combination.

Note

Limitations

  • The accuracy of altimetric discharge estimations decreases for narrower rivers. Over the years the size of rivers having altimetry-built water level time series has decreased from 2-3 km to 80 m. The errors of level estimates has also been reduced: for large rivers to 0.30 m and for medium size rivers to 0.20 m.

  • The accuracy of water height retrievals depends strongly on river fluvial morphology. Large river width, low banks, and the absence of the sand islands are the main favorable conditions for precise estimation of water level.

Info

Applicability for Northland

Yes, possibly depending on the resolution of imagery available and characteristics of the rivers of interest.

Publication references

📚 Zakharova E, Nielsen K, Kamenev G, Kouraev A. 2020. River discharge estimation from radar altimetry: Assessment of satellite performance, river scales and methods. Journal of Hydrology. 583:124561. doi:10.1016/j.jhydrol.2020.124561.

🔗 https://orbit.dtu.dk/en/publications/river-discharge-estimation-from-radar-altimetry-assessment-of-sat

(info) Other comments or information

The accuracy of discharge estimation from altimetric satellite observations depends on the accuracy of the satellite-retrieved variables (water height and water slope), the accuracy of the algorithm parameterisation
and the degree of simplification (generalisation) of the hydrological processes within the applied algorithms.

Other references

📚 Hou J, van Dijk AIJM, Beck HE. 2020. Global satellite-based river gauging and the influence of river morphology on its application. Remote Sensing of Environment. 239:111629. doi:10.1016/j.rse.2019.111629.
🔗 https://www.sciencedirect.com/science/article/pii/S0034425719306492

📚 Feng D, Gleason CJ, Yang X, Pavelsky TM. 2019. Comparing Discharge Estimates Made via the BAM Algorithm in High-Order Arctic Rivers Derived Solely From Optical CubeSat, Landsat, and Sentinel-2 Data. Water Resources Research. 55(9):7753-7771. doi:10.1029/2019WR025599.

🔗 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019WR025599

...