Yes, it really does rain in the Arizona deserts, in the summer and winter, and the summer rain pattern is called the Monsoon. When these rains finally come, and they were a bit late this year, the dry riverbeds fill with very powerful flowing water. Here are some photos of the Santa Cruz River, usually only a few feet wide and inches deep with treated water from the facility a little bit downstream. This past morning I took a walk on a paved walkway on the riverbank on my way home from work, and this is what I saw.
The ducks are a bit of a bonus, though they are frequently swimming around.