Abstract
Abstract. This study presents an approach to determining the volume of water in small lakes (<100 ha) by combining satellite altimetry data and high-resolution (HR) images. In spite of the strong interest in monitoring surface water resources on a small scale using radar altimetry and satellite imagery, no information is available about the limits of the remote-sensing technologies for small lakes mainly used for irrigation purposes. The lake being studied is located in the south-west of France and is only used for agricultural irrigation purposes. The altimetry satellite data are provided by an RA-2 sensor onboard Envisat, and the high-resolution images (<10 m) are obtained from optical (Formosat-2) and synthetic aperture radar (SAR) antenna (Terrasar-X and Radarsat-2) satellites. The altimetry data (data are obtained every 35 days) and the HR images (77) have been available since 2003 and 2010, respectively. In situ data (for the water levels and volumes) going back to 2003 have been provided by the manager of the lake. Three independent approaches are developed to estimate the lake volume and its temporal variability. The first two approaches (HRBV and ABV) are empirical and use synchronous ground measurements of the water volume and the satellite data. The results demonstrate that altimetry and imagery can be effectively and accurately used to monitor the temporal variations of the lake (R2ABV = 0.98, RMSEABV = 5%, R2HRBV = 0.90, and RMSEABV = 7.4%), assuming a time-varying triangular shape for the shore slope of the lake (this form is well adapted since it implies a difference inferior to 2% between the theoretical volume of the lake and the one estimated from bathymetry). The third method (AHRBVC) combines altimetry (to measure the lake level) and satellite images (of the lake surface) to estimate the volume changes of the lake and produces the best results (R2AHRBVC = 0.98) of the three methods, demonstrating the potential of future Sentinel and SWOT missions to monitor small lakes and reservoirs for agricultural and irrigation applications.
Highlights
Water supply issues are creating unprecedented pressures because of increasing population and economic demands
Baup et al.: Combining high-resolution satellite images and altimetry dramatic decrease in the number of in situ gauges used in recent years and the difficulty in modelling water resources on a global scale, measuring water stages by remote sensing and especially by satellite has become a major goal in hydrology for the coming decades (The Ad Hoc Group on Global Water Datasets, 2001; Alsdorf et al, 2007; Duan and Bastiaanssen, 2013)
In the third method (AHRBVC), the lake surface from the HR images was combined with altimetry-based water levels that were acquired quasi synchronously
Summary
Water supply issues are creating unprecedented pressures because of increasing population and economic demands. Water resources can be monitored on a global scale using three approaches: in situ measurements, modelling, and remote-sensing observations (Jorgensen et al, 2005; Harding and Warnaars, 2011; Hall et al, 2011; Duan and Bastiaanssen, 2013). F. Baup et al.: Combining high-resolution satellite images and altimetry dramatic decrease in the number of in situ gauges used in recent years and the difficulty in modelling water resources on a global scale (because of complex mixing between inflows and outflows), measuring water stages by remote sensing and especially by satellite has become a major goal in hydrology for the coming decades (The Ad Hoc Group on Global Water Datasets, 2001; Alsdorf et al, 2007; Duan and Bastiaanssen, 2013)
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