Abstract
he quantification of river discharge is essential for
understanding a broad range of scientific questions
focused on hydrology, hydraulics and water resource
management. However, the Global Runoff Data Center
(GRDC) data set has faced a decline in the number of
active gauges since the 1980s, leaving only 14% of
gauges active as of 2020. For extending the discharge
estimates of inactive GRDC stations, we develop the
Remote Sensing-based Extension for the GRDC (RSEG)
data set that can ingest legacy gauge discharge and
remote sensing observations.
First, we evaluated the feasibility of extending discharge
estimates of gauges in the GRDC dataset benefiting
from river water height time series obtained from
satellite altimetry missions (2000--2020) and river width
estimates obtained from Landsat 4-8 mission images
(1984–2020). Then we employ a stochastic
nonparametric mapping algorithm to extend the
discharge time series for inactive GRDC stations,
benefiting from satellite imagery- and altimetry-derived
river width and water height observations. Finally, we
conduct a rigorous quality assessment on our discharge
estimates, involving statistical validation, tests and
visual inspection, resulting in the salvation of discharge
records for 3377 out of 6015 GRDC stations with an
average discharge exceeding 10 m^3/s. The quality of
discharge estimates for the rivers with a large or
medium mean discharge is quite satisfactory (average
KGE value > 0.5) however for river reaches with a low
mean discharge the average KGE value drops to 0.33.
The RSEG data set regains monitoring capability for 83%
of total river discharge measured by GRDC stations,
equivalent to 7895 km^3/month, providing valuable
insight into Earth’s river systems with comprehensive
and up-to-date information.
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