Exploratour - The Surface of Mars
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Martian Lakes
Separate from the Martian outflow channels, or the river valley networks, are large Martian lakes (600 km, or ~1000 miles across) which exhibit evidence of a periodic and catastrophic release of water in the form of floods.
This evidence suggests the possibility of an equilibrium between the lakes and an aquifer lying close to the surface. As the lake level drops, water comes to it from the aquifer. Evaporation of water from the lake and recondensation close to the surrounding terrain would return water to the aquifer.