If it had filled to form a lake
then there would be noticeable shorelines etc.
If, however, the fans and streams are merely dry dust/sand and rock flows - which it looks like to me - then there wont be.
I'd love there to be use-able water on Mars but pretending its the only thing that can create these features is going to get us no where and may waste a few billion on a trip to see something you can find in a sandpit here on earth.
It is not a dried out river - it was a river of dry material flowing like a liquid. Earthquakes (or nearby meteorite strikes) shake the rubble into a liquid type form and it flows in ways similar to a liquid.
The only other explanation would be for a localised rainstorm of unimaginable power over that little area and nowhere else nearby.