Producing time series of river water height by means of satellite radar altimetry—a comparative study

Abstract

Satellite radar altimetry is complementary to in situ limnimetric surveys as a means of estimating the water height of large rivers, lakes and flood plains. Production of water height time series by satellite radar altimetry technology requires first the selection of radar ground target locations corresponding to water body surfaces under study, i.e. the definition of "virtual limnimetric stations". We propose to investigate qualitative and quantitative differences between three representative virtual station creation methodologies: (a) a fully manual method, (b) a semi-automatic method based on a land cover characterization that allows the water body surface under study to be located; and (c) an original fully automatic procedure that exploits a digital elevation model and an estimation of the river width. The results yielded by these three methods are comparable: maximum absolute magnitudes of water height differences being 0.46, 0.26 and 0.15 m for, respectively, 95, 90 and 80% of the water height values obtained. Moreover, more than 67% and 92% of time series jointly produced by the methods present root mean square differences lower than 20 and 50 cm, respectively. The results show that the fully automatic method developed herein provides as reliable results as the fully manual one. This opens the way to use of satellite radar altimetry for the generation of water height time series on a large scale, and considerably extends the applicability of satellite radar altimetry in hydrology. Key words

Correction of Interferometric and Vegetation Biases in the SRTMGL1 Spaceborne DEM with Hydrological Conditioning towards Improved Hydrodynamics Modeling in the Amazon Basin

“…Many studies have now shown the great ability of radar altimetry missions for retrieving river stages [53][54][55][56][57]. In this study, we used data from three different radar altimeters, namely ENVISAT/RA-2, T/P and ICESat/GLAS, available through the CTOH website (Centre de Topographie des Océans et de l'Hydrosphère) [58].…”

“…Satellite radar altimetry provided 5 additional virtual stations from the T/P and ENVISAT missions. The manual method described in [53,59] was used to build the virtual gauges, which can be defined as any intersection between a water body surface and radar altimetric ground tracks. Three virtual stations were gained from the ENVISAT mission ( Figure 1): SV2 (3.493˝S, 60.253˝W) in the upstream zone, SV1 (3.392˝S, 60.239˝W) in the downstream zone and SVR (3.325˝S, 60.220˝W) in the Solimões.…”

Monitoring water level in large trans-boundary ungauged basins with altimetry: the example of ENVISAT over the Amazon basin

“…In all other situations, manual extraction has been performed, with results slightly better (lower standard deviation and more cycles sampled) than the automatic one. The automatic extraction has been found to be more reproductible, and not statistically different than the manual one 16 . The reproductibility criteria is certainly best fulfilled by the automatic method, but it seems that in the cases where the river is mostly perpendicular to the flow direction, with small width, and extensive floodplain, the manual extraction can be the best method to employ.…”

An improved methodology to estimate river stage and discharge using Jason-2 satellite data

“…Hence, many methodologies have been developed for selection of waveform over the inland water bodies, i.e. defining the virtual station (Berry et al, 2005;Leon, 2006;Kouraev et al, 2004;Zakharova et al, 2006;Roux et al, 2010). In many of the research studies over large rivers, virtual stations are defined using the satellite information of river flow characteristics.…”