Abstract
Lakes are key components of biogeochemical and ecological processes, thus knowledge about their distribution, volume and residence time is crucial in understanding their properties and interactions within the Earth system. However, global information is scarce and inconsistent across spatial scales and regions. Here we develop a geo-statistical model to estimate the volume of global lakes with a surface area of at least 10 ha based on the surrounding terrain information. Our spatially resolved database shows 1.42 million individual polygons of natural lakes with a total surface area of 2.67 × 106 km2 (1.8% of global land area), a total shoreline length of 7.2 × 106 km (about four times longer than the world's ocean coastline) and a total volume of 181.9 × 103 km3 (0.8% of total global non-frozen terrestrial water stocks). We also compute mean and median hydraulic residence times for all lakes to be 1,834 days and 456 days, respectively.
Highlights
Lakes are key components of biogeochemical and ecological processes, knowledge about their distribution, volume and residence time is crucial in understanding their properties and interactions within the Earth system
Given the observation that shoreline length is dominated by smaller lake size classes (Table 1; confirmed by Winslow et al.24) we assume that these estimates are significantly underestimating global shoreline length as lakes below 10 ha are not included
Our results depend on map scale that defines how finely the shorelines are resolved, and it has been observed that a doubling of measurement resolution will cause shoreline length to increase by 15%
Summary
Lakes are key components of biogeochemical and ecological processes, knowledge about their distribution, volume and residence time is crucial in understanding their properties and interactions within the Earth system. Previous estimates of the total global volume of water contained in lakes ranged from 166 to 275 Â 103 km[3] (refs 13–16), with more recent figures converging to 176–180 Â 103 km[3] (refs 17–19) These estimates are not spatially explicit, are based on incomplete data sets of lake distribution or use simple extrapolation methods that rely on a limited set of variables. While large lakes might dominate processes driven by volume or surface area due to their prevalence at a global scale, small lakes contribute more to the total aquatic–terrestrial interface than large lakes[24] It remains inconclusive how different size classes might relate in terms of residence time. While optical remote sensing methods have been widely used for bathymetric mapping of coastal benthic habitats for several decades[26] these techniques are still limited to shallow environments and favourable water conditions[27]
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