Sentinel 3 Ruaha River Water Levels
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Last Updated 1 month ago
A first verification (below) of the Sentinel-3 remote river water level data from Hydroweb from two virtual stations (VS) of the Ruaha River in the Ruaha National Park, justifies further follow up.
The frequence of the Hydroweb data selected is not adequate to replace the current zero flow methodology for the Ruaha River (MajiYetu) but if reliable the method can be applied for verification and used elsewhere in Tanzania. Potential applications are remote Lake/Reservoir water level storage monitoring and remote flow estimates of ungauged rivers. Minimum width of water surfaces for VS in a study (download) testing a method to record seasonal flooding in Zambezi Wetlands, shows a minimum water surface of 35 m with good results.
The accurracy and flexibility of the location of the VS will matter while the Ruaha riverbed is dynamic and channels can re-route with the VS left on a dry river- or sandbank. This may have been the case with the second VS in the Ruaha River with coordinates lat:-7.5668 and lon:35.0347.
In this post we look into the VS with id “105849” with an uncertainty of min. -/+ 1cm to max. +/-83cm. among 42 records.
The difference between flow and no-flow in the VS section of the Ruaha River is a remotely recorded water level difference of just 26 cm. On December 5th, 2021 the water level (“no flow”) is 931.01 m (to vertical reference point) while on December 19, 2020 with “flow” in the river the level is 931.27 m.
The data in the graph for the VS (105849) provide ranges for a zero flow threshold. Assuming the uncertainties of respectively +/- 0.06 and +/- 0.14 for both critical values, gives a min. range 6cm between 931.15m (flow) and 931.21m (no-flow) and max. range (54cm) between 931.33m and 930.87m for the threshold.
The Sentinel-2 satellite images related to the Sentinel-3 water level altimeter records, for both dates of the threshold assessment are within a few days. The original data are found here. (a free account is required).
