Counting the number of lakes in the world until recently was more of a guessing game than an exact science. A recently study published in Geophysical Research Letters used satellite data to remotely sense the number of lakes larger than 0.002 square kilometers. An automated algorithm called GWEM (GeoCoverTM Water bodies Extraction Method) was used on cloud-free Landsat satellite imagery to extract information about the number and size of lakes around the world, excluding the world’s largest inland water body, the Caspian sea, Antarctica, and the glaciated areas of Greenland. Researchers found that there are 117 million lakes larger than 0.002 km2 in the world which collectively cover 3.7% of Earth’s nonglaciated land area.
Previous counts extrapolated the number of the lakes based on computer models that have turned out to be inaccurate. In 2006, a study used a global model based on the Pareto distribution to estimate that there are 304 million lakes covering 4.2 million km2 in area, a calculation that turned out to grossly overestimate the number of lakes.
Geographic Distribution of Lakes
About 22 million water bodies larger than 0.01 km2 are located between 60°N and 56°S which is the area where elevation data is available and collectively represent 1.4% of the world’s nonglaciated surface. A greater surface area of lakes exists north of 60°N or south of 56°S where there are about 5 million lakes. The greatest concentration of lakes (Figures a, c, e) can be found at the boreal and arctic latitudes (45°–75°N). Elevation also plays a role in lake size and abundance with 85% of lakes, 50% of lake area, and 50% of total lake perimeter being located at elevations lower than 500 meters above sea level (Figures b, d, and f ).
Verpoorter, C., T. Kutser, D. A. Seekell, and L. J. Tranvik (2014), A global inventory of lakes based on high-resolution satellite imagery, Geophys. Res. Lett., 41, doi:10.1002/2014GL060641.