14 research outputs found
A review of the potential to establish a global, operational river monitoring based on Sentinel-3 water surface elevation observations
Informing a hydrological model of the Ogooué with multi-mission remote sensing data
Remote sensing provides a unique opportunity to inform and constrain a hydrological
model and to increase its value as a decision-support tool. In this study, we
applied a multi-mission approach to force, calibrate and validate a
hydrological model of the ungauged Ogooué river basin in Africa with
publicly available and free remote sensing observations. We used a
rainfall–runoff model based on the Budyko framework coupled with a Muskingum
routing approach. We parametrized the model using the Shuttle Radar
Topography Mission digital elevation model (SRTM DEM) and forced it using
precipitation from two satellite-based rainfall estimates, FEWS-RFE (Famine
Early Warning System rainfall estimate) and the Tropical Rainfall Measuring
Mission (TRMM) 3B42 v.7, and temperature from ECMWF ERA-Interim. We combined
three different datasets to calibrate the model using an aggregated objective
function with contributions from (1) historical in situ discharge
observations from the period 1953–1984 at six locations in the basin,
(2) radar altimetry measurements of river stages by Envisat and Jason-2 at 12
locations in the basin and (3) GRACE (Gravity Recovery and Climate
Experiment) total water storage change (TWSC). Additionally, we extracted CryoSat-2
observations throughout the basin using a Sentinel-1 SAR (synthetic aperture
radar) imagery water mask and used the observations for validation of the
model. The use of new satellite missions, including Sentinel-1 and CryoSat-2,
increased the spatial characterization of river stage. Throughout the basin,
we achieved good agreement between observed and simulated discharge and the
river stage, with an RMSD between simulated and observed water amplitudes at
virtual stations of 0.74 m for the TRMM-forced model and 0.87 m for the
FEWS-RFE-forced model. The hydrological model also captures overall total
water storage change patterns, although the amplitude of storage change is
generally underestimated. By combining hydrological modeling with
multi-mission remote sensing from 10 different satellite missions, we obtain
new information on an otherwise unstudied basin. The proposed model is the
best current baseline characterization of hydrological conditions in the
Ogooué in light of the available observations
Monitoring of surface water resources in East Africa using CryoSat-2 radar altimetry and Sentinel-1 SAR imagery
Technical note: Bathymetry observations of inland water bodies using a tethered single-beam sonar controlled by an unmanned aerial vehicle
High-quality bathymetric maps of inland water bodies are a common
requirement for hydraulic engineering and hydrological science applications.
Remote sensing methods, such as space-borne and airborne multispectral
imaging or lidar, have been developed to estimate water depth, but are
ineffective for most inland water bodies, because of the attenuation of
electromagnetic radiation in water, especially under turbid conditions.
Surveys conducted with boats equipped with sonars can retrieve accurate water
depths, but are expensive, time-consuming, and unsuitable for unnavigable
water bodies.We develop and assess a novel approach to retrieve accurate and high-resolution bathymetry maps. We measured accurate water depths using a
tethered floating sonar controlled by an unmanned aerial vehicle (UAV) in a
lake and in two different rivers located in Denmark. The developed technique
combines the advantages of remote sensing with the potential of bathymetric
sonars. UAV surveys can be conducted also in unnavigable, inaccessible, or
remote water bodies. The tethered sonar can measure bathymetry with an
accuracy of ∼ 2.1 % of the actual depth for observations up to
35 m, without being significantly affected by water turbidity, bed form, or
bed material.</p