Abstract
Abstract. The recent availability of freely and openly available satellite remote sensing products has enabled the implementation of global surface water monitoring at a level not previously possible. Here we present a global set of satellite-derived time series of surface water storage variations for lakes and reservoirs for a period that covers the satellite altimetry era. Our goals are to promote the use of satellite-derived products for the study of large inland water bodies and to set the stage for the expected availability of products from the Surface Water and Ocean Topography (SWOT) mission, which will vastly expand the spatial coverage of such products, expected from 2021 on. Our general strategy is to estimate global surface water storage changes (ΔV) in large lakes and reservoirs using a combination of paired water surface elevation (WSE) and water surface area (WSA) extent products. Specifically, we use data produced by multiple satellite altimetry missions (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, and Envisat) from 1992 on, with surface extent estimated from Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 on. We leverage relationships between elevation and surface area (i.e., hypsometry) to produce estimates of ΔV even during periods when either of the variables was not available. This approach is successful provided that there are strong relationships between the two variables during an overlapping period. Our target is to produce time series of ΔV as well as of WSE and WSA for a set of 347 lakes and reservoirs globally for the 1992–2018 period. The data sets presented and their respective algorithm theoretical basis documents are publicly available and distributed via the Physical Oceanography Distributed Active Archive Center (PO DAAC; https://podaac.jpl.nasa.gov/, last access: 13 May 2020) of NASA's Jet Propulsion Laboratory. Specifically, the WSE data set is available at https://doi.org/10.5067/UCLRS-GREV2 (Birkett et al., 2019), the WSA data set is available at https://doi.org/10.5067/UCLRS-AREV2 (Khandelwal and Kumar, 2019), and the ΔV data set is available at https://doi.org/10.5067/UCLRS-STOV2 (Tortini et al., 2019). The records we describe represent the most complete global surface water time series available from the launch of TOPEX/Poseidon in 1992 (beginning of the satellite altimetry era) to the near present. The production of long-term, consistent, and calibrated records of surface water cycle variables such as in the data set presented here is of fundamental importance to baseline future SWOT products.
Highlights
Information about surface water dynamics is required to support monitoring and reporting programs associated with water management as well as to support scientific objectives such as understanding the space–time variability in water stored at or near the land surface (Lettenmaier and Famiglietti, 2006)
With the recent availability of free and open-access satellite remote sensing products, users have access to high-quality, analysis-ready imagery at spatial resolutions that are informative at the relevant scales about variation in water surface elevation (WSE) and water surface area (WSA), and storage, at least for relatively large inland water bodies
Global water dynamics studies that previously would have only been approachable with relatively low spatial resolution data sets or gravimetric remote sensing such as GRACE (e.g., Humphrey et al, 2016) are implemented using high-resolution imagery such as Landsat
Summary
Information about surface water dynamics is required to support monitoring and reporting programs associated with water management as well as to support scientific objectives such as understanding the space–time variability in water stored at or near the land surface (Lettenmaier and Famiglietti, 2006). Surface water storage data are scarce and often inaccessible in many regions of the world due to geographic remoteness and/or closed data policies in addition to the costs associated with maintaining extensive water monitoring programs This is especially the case in areas with sparse populations and in the developing world, limiting our ability to understand the surface water balance at the global scale and its effect on water management planning, global weather forecasting, ecosystem sustainability, and earth system modeling in general (Gao, 2015). With the recent availability of free and open-access satellite remote sensing products, users have access to high-quality, analysis-ready imagery at spatial resolutions that are informative at the relevant scales about variation in water surface elevation (WSE) and water surface area (WSA), and storage, at least for relatively large inland water bodies. Crétaux et al (2016) estimated that the constellation of Jason-2, Jason-3, the France–India SARAL AltiKa mission (Verron et al, 2015), and the European Space Agency’s Sentinel-3 tandem (Donlon et al, 2012) has the potential to capture water surface elevation (WSE) for nearly the entirety of 3720 global lakes with areas larger than 50 km and 71 % of the 14 411 lakes larger than 10 km, for a total of approximately 40 % of the global water storage of lakes on Earth
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