English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Remote sensing and satellite geodetic observations are capable of hydrologicmonitoring of freshwater resources. Although satellite radar altimetry hasbeen used in monitoring water level or discharge, its use is often limited tomonitoring large rivers (>1 km) with longer interval periods (>1week) because of its low temporal and spatial resolutions (i.e., satelliterevisit period). Several studies have reported successful retrieval of waterlevels for small rivers as narrow as 40 m. However, processing currentsatellite altimetry signals for such small water bodies to retrieve waterlevels accurately remains challenging. Physically, the radar signal returnedby water bodies smaller than the satellite footprint is most likelycontaminated by non-water surfaces, which may degrade the measurementquality. In order to address this scientific challenge, we carefully selectedthe waveform shapes corresponding to the range measurement resulting fromstandard retrackers for the European Space Agency's (ESA's) Envisat(Environmental Satellite) radar altimetry. We applied this approach to small(40–200 m in width) and medium-sized (200–800 m in width) rivers andsmall lakes (extent <1000 km<sup>2</sup>) in the humid tropics of SoutheastAsia, specifically in Indonesia. This is the first study that explored theability of satellite altimetry to monitor small water bodies in Indonesia.  The major challenges in this study include the size of the water bodies thatare much smaller than the nominal extent of the Envisat satellite footprint(e.g., ~250 m compared to ~1.7 km, respectively) and slightlysmaller than the along-track distance (i.e., ~370 m). We addressedthis challenge by optimally using geospatial information and optical remotesensing data to define the water bodies accurately, thus minimizing theprobability of non-water contamination in the altimetry measurement.Considering that satellite altimetry processing may vary with differentgeographical regions, meteorological conditions, or hydrologic dynamic, wefurther evaluated the performance of all four Envisat standard retrackingprocedures.  We found that satellite altimetry provided a good alternative or the onlymeans in some regions of measuring the water level of medium-sized rivers andsmall lakes with high accuracy (root mean square error (RMSE) of0.21–0.69 m and a correlation coefficient of 0.94–0.97). In contrast toprevious studies, we found that the commonly used Ice-1 retracking algorithmwas not necessarily the best retracker among the four standard waveformretracking algorithms for Envisat radar altimetry observing inland waterbodies. As a recommendation, we propose to include the identification andselection of standard waveform shapes to complete the use of standardwaveform retracking algorithms for Envisat radar altimetry data over smalland medium-sized rivers and small lakes

Satellite radar altimetry for monitoring small rivers and lakes in Indonesia