Real-time remote sensing driven river basin modeling using radar altimetry

Abstract

Abstract. Many river basins have a weak in-situ hydrometeorological monitoring infrastructure. However, water resources practitioners depend on reliable hydrological models for management purposes. Remote sensing (RS) data have been recognized as an alternative to in-situ hydrometeorological data in remote and poorly monitored areas and are increasingly used to force, calibrate, and update hydrological models.In this study, we evaluate the potential of informing a river basin model with real-time radar altimetry measurements over reservoirs. We present a lumped, conceptual, river basin water balance modeling approach based entirely on RS and reanalysis data: precipitation was obtained from the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA), temperature from the European Centre for Medium-Range Weather Forecast's (ECMWF) Operational Surface Analysis dataset and reference evapotranspiration was derived from temperature data. The Ensemble Kalman Filter was used to assimilate radar altimetry (ERS2 and Envisat) measurements of reservoir water levels. The modeling approach was applied to the Syr Darya River Basin, a snowmelt-dominated basin with large topographical variability, several large reservoirs and scarce hydrometeorological data that is located in Central Asia and shared between 4 countries with conflicting water management interests.Correspondence to: P. Bauer-Gottwein (pbau@env.dtu.dk)The modeling approach was tested over a historical period for which in-situ reservoir water levels were available. Assimilation of radar altimetry data significantly improved the performance of the hydrological model. Without assimilation of radar altimetry data, model performance was limited, probably because of the size and complexity of the model domain, simplifications inherent in model design, and the uncertainty of RS and reanalysis data. Altimetry data assimilation reduced the mean absolute error of the simulated reservoir water levels from 4.7 to 1.9 m, and overall model RMSE from 10.3 m to 6.7 m. Model performance was variable for the different reservoirs in the system. The RMSE ranged from 10% to 76% of the mean seasonal reservoir level variation.Because of its easy accessibility and immediate availability, radar altimetry lends itself to being used in real-time hydrological applications. As an impartial source of information about the hydrological system that can be updated in real time, the modeling approach described here can provide useful medium-term hydrological forecasts to be used in water resources management.

A review of applications of satellite SAR, optical, altimetry and DEM data for surface water modelling, mapping and parameter estimation

“…Owe et al (2001) also compiled papers presented at a conference on applications of remote sensing in many aspects of hydrology. Beyond mapping, satellite data in the form of imagery, a digital eleva- tion model (DEM), altimetry data, etc., can be used as hydraulic model input forcing factors or to constrain model data during calibration/validation/verification (Pereira-Cardenal et al, 2011). Satellite-based estimates of river flow, river width, water levels and flooding extent are used for model calibration/validation/verification.…”

“…Penton and Overton (2007) combined flood mask extents from LandSat ETM of four flood events with a lidar DEM to produce water heights for the floodplain. The heights of the flood mask water points were used to interpolate a water height surface which was subtracted from the DEM to produce the inundation map.…”

“…Hydrological data collection still remains a difficult task nowadays due to non-availability of measurement devices, inaccessibility of the terrain and limitations of space/time (Quin et al, 2010;Pereira-Cardenal et al, 2011). A good alternative to overcome these difficulties is use of satellite remote sensing, which can give a synoptic view of target areas ( Fig.…”

River Discharge Estimation by Using Altimetry Data and Simplified Flood Routing Modeling

“…Few studies dedicated to a thorough assessment of the radar altimetry over rivers, such as Ob, Mekong, Negro, Gange and Brahmaputra, even without comparisons with in situ gauges, have been published [7,[20][21][22][23][24][25]. The accuracy of altimeter water level time series over river and floodplains has been discussed in several previously published papers (i.e., [14,15,26]).…”

“…The high accuracy of altimetry data provided by the latest spatial missions and the convincing results obtained in the previous applications suggest that these data may also be employed for hydrological model calibration [22,23,[28][29][30]. Using hydrological models calibrated with in situ data in other sites in the basin, Leon et al [17] and Getirana et al [22] developed methods to derive rating curves at VS locations based on altimetry levels and modeled discharges.…”