Inside the question engineOpen the field notes
Both lakes use the same scale and an equal-area projection, so their visible surfaces retain the true proportion. The question, however, is about volume, which also depends on depth. The volume difference becomes smaller at each stage.
The lake volume quiz: how it works
This quiz tests whether you can tell a lake's surface area from the amount of water it holds. You see both lakes at the same scale, but volume also depends on depth, which a map cannot show.
How does the quiz pick the pairs of lakes?
Each round has 10 questions. Pairs are drawn from 18 lakes with a verified volume, and no pair repeats within a round. The volume gap between the answers shrinks at each stage: from 50% to 150% in the first questions to only 2% to 8% in the last ones.
Where do the lake areas and volumes come from?
Areas and volumes come from the source assigned to each lake: Encyclopaedia Britannica and the US Environmental Protection Agency (published 2023 and 2024). Outlines come from Natural Earth data.
A fact: surface area versus volume
The largest surface in the pool belongs to Lake Superior (82,100 km²), but Lake Baikal holds the most water: 23,615 km³ compared with 12,100 km³.
Frequently asked questions
How do you work out a lake's average depth?
Divide the volume by the surface area. In the quiz data: Lake Baikal averages about 740 m, and Lake Winnipeg about 12 m.
Are seas and oceans in this quiz too?
No. This quiz uses only lakes with a verified volume: 18. Seas and oceans are in the quizzes “Name the water body” and “Water or land”.
Where can I find the data on each lake in the quiz?
Each of the 18 lakes has its own profile on this site with its area, volume and source. The profiles are in the lake catalog.