"From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep," said Curiosity science co-investigator William Dietrich of the University of California, Berkeley.
Out of interest, how do we know it was water, and not some other liquid?
A good piece of evidence is that the dust of Mars is significantly composed of 'goethite', essentially hydrated iron rust. There's an awful lot of dust, and if you do the work backwards you can get a decent idea of how much water it took to make it happen.
Furthermore, most liquids found at reasonable temperatures aren't all that voluminous, and a number of the minerals scanned and inspected on Mars show evidence of water contact.
Basically, there's not much else it could be. :) That said there's some really cool theorizing on underground carbon dioxide flows that might explain some washouts seen later in Mars's life.
Almost! The blueberries are hematite, Fe2O3, an iron oxide. Goethite is FeO(OH), an iron oxyhydroxide. Both strongly indicate water went in to making them but the blueberries imply they were submerged in water whereas goethite doesn't necessary require anything but water vapor.
How does the lower gravity affect that? Does the lower gravity mean the rocks are easier to carry, or does the lower gravity mean the water flows slower?
Out of interest, how do we know it was water, and not some other liquid?