Photo: NASA

How many lakes are on Earth and how big are they?

Summary

How many lakes are there and how big are they? This is one of the most fundamental questions in limnology. This project uses theoretical and empirical analyses to evaluate the global abundance and size-distribution of lakes. To date, the project has created the first global lake census based on high-resolution satellite imagery, and the first theoretically-grounded estimate of global lake volume. Current work focuses on the characteristics of lake size-distributions, their topographic correlates, and their potential as a constraint on broader-scale ecological patterns. Results from this project have been communicated to the scientific community through journal articles and conference presentations, and to the general public through news and social media.

Project Status

Ongoing

Project Description

Examination of maps or satellite images reveals the size-distribution of Earth’s lakes is strongly skewed: there are many small lakes, but few large lakes. Most key ecosystem processes in lakes scale strongly with lake surface area, and therefore, the size-distribution of lakes is a fundamental constraint on patterns in lake ecology and biogeochemistry at broad geographic scales. In particular, an accurate characterization of Earth’s lake size-distribution is critical for estimating global rates of lake productivity and greenhouse gas emissions.

This project began with the observation that the size-distribution of lakes is not a power-law for small lakes. At the time, the power-law form was a widely held assumption and this observation indicated that previous estimates of global lake abundance and surface area may have incorporated large errors. Deviation from a power-law form has been independently confirmed several times (see: McDonald et al. 2012, Muster et al. 2013, Zhang et al. 2014, Paltan et al. 2015, Muster et al. 2019). Subsequently, I was involved with the first global lake census based on high-resolution satellite imagery, the first characterization of the size-distribution of these data, and the first theoretically-grounded estimate of global lake volume. These studies have found that large lakes are power-law distributed, but that small lakes deviate from the power-law distribution beginning at approximately the same scale that topography looses scale-free characteristics. In general, there are far fewer small lakes than early estimates suggested. The total volume of lakes is small - if poured into a sphere, the diameter would only stretch between Boston, Massachusetts and Providence, Rhode Island. The overall mean depth is only 40-60 meters, depending on what estimate of global lake area is used. For context, the mean depth of the global ocean is 3682 meters and the mean elevation of the land surface is 797 meters.

The current focus of this project is on the characteristics of lake size-distributions, their topographic correlates, and their potential as a constraint on broader-scale ecological patterns. This research, which is based partly on computer simulations and partly on novel empirical analyses, is being conducted during the period 2017-2020.

The volume-surface area for lakes is predictable based on the Hurst coefficient of Earth’s topography. We used this relationship to estimate the volume of Earth’s lakes.

The results of this project form the basis for upscaling the chemical and biological features of lakes to understand the contributions of lakes to the Earth system. They reveal some of the most fundamental characteristics of lakes, which have far reaching importance to limnological studies. Cover of Geophysical Research Letters

Selected Media Reports

Press Releases

Publications

. Fractal Characteristics of lakes. Thule (Kungl. Skytteanska samfundets årsbok), 2018.

Preprint Project

. The volume and mean depth of Earth’s lakes. Geophysical Research Letters, 2017.

PDF Project Video Graphical Abstract

. The size-distribution of Earth’s lakes. Scientific Reports, 2016.

PDF Project

. A global inventory of lakes based on high-resolution satellite imagery. Geophysical Research Letters, 2014.

PDF Project

. A fractal-based approach to lake size-distributions. Geophysical Research Letters, 2013.

PDF Project Journal Cover Editor's Highlight

. Does the Pareto distribution adequately describe the size-distribution of lakes?. Limnology & Oceanography, 2011.

PDF Project