Lakes of Aargau 2026: 11, its biggest own lake a reservoir

The largest lake entirely in Aargau is not Lake Hallwil. Which one then? ↓

Lake Hallwil counts as an Aargau lake, but part of it belongs to Lucerne. The largest lake lying entirely in Aargau is a river reservoir: the Klingnauer Stausee, 1.06 km².

Number of lakes in Aargau: 11

11 lakes of half a hectare or more, and yet the national map shows 908 bodies of standing water in Aargau. The gap is not imprecision; it is a way of counting.

Anyone reading a different figure has almost always drawn a different line: count every water surface and Aargau has 908; count only lakes over one square kilometre and you get 2. Even a plain name such as "Weiher" counts as official: what decides is the entry in the swissNAMES3D gazetteer. Our count states where the line is, so it can be checked.

Lake Finder: find any lake in Aargau

Largest lake in Aargau: Klingnauer Stausee

The largest lake touching Aargau is the Hallwilersee (10.2 km²), but only 85% of its surface lies in the canton. The largest lake belonging entirely to the canton is the Klingnauer Stausee: 1.06 km² at 319 m.

Highest lake in Aargau: Ägelsee

Even the highest lake in Aargau lies lower than 75% of Swiss lakes: the Ägelsee in Bergdietikon at 667 m, 2.5 ha.

The canton's lowest-lying lake is the Klingnauer Stausee at 319 m. The canton's median lake sits at 401 m. Elevation is the water level in the landscape model; for reservoirs it varies with how full they are.

Shared lakes: which lakes Aargau shares

88% of the lake surface in Aargau lies in lakes it does not own alone. Aargau shares 1 of its 11 lakes with other cantons; the table shows how much of each lies in the canton.

List of lakes in Aargau

9 of the 11 lakes in Aargau together cover less area than a single lake, Klingnauer Stausee: 14 ha against 1.06 km². An official name does not make a lake: 13 of the 24 named bodies of water in Aargau measure less than half a hectare. The list shows all of them by area, the 11 lakes first, the smaller ones marked.

Lakes by size: 9 of 11 under 5 ha

9 of the 11 lakes in Aargau are smaller than five hectares. 2 are larger than ten hectares, which puts Aargau at rank 18 of the 26 cantons.

Measured by area, the small lakes almost vanish: the 9 of the 11 lakes of half a hectare or more that stay under five hectares together cover about 1% of the lake surface in Aargau. Hallwilersee, counting only its part in the canton, alone covers 88%.

More lake pages

Written by

Marco Gisler

ConvivaPlus Editor · Data & Switzerland

Writes about Switzerland in figures – official data recalculated, counting method explained.

• Population
• 26 cantons
• Waterways
• Official data

Researched & sourced · for Switzerland

Profile & all articles →·Our editorial teamUpdated 25.10.2026

Source: swisstopo (swissTLM3D, swissNAMES3D, swissBOUNDARIES3D, 2026 edition), analysis by ConvivaPlus. Switzerland as a whole: 891 lakes out of 17'873 water surfaces; parts with the same name no more than 50 m apart count as one lake. Area = water surface at the shoreline of the landscape model; reference works using a different shoreline or water level sometimes give other values.