Even though there is a lake there now, it is an artificial lake with operable dams on the west side and only dates back to 1998 or so. Prior to the damming of the Salt and Verde Rivers in the 30's as part of WPA project to provide reservoirs and hydro electric power in the mountains NE of town for the Phoenix area farms in the 1930's, the Salt River ran all year round. The Army Corps regulates it as a navigable river and about every 5 years or so due to heavy summer rains, there are controlled releases into what is mostly a dry river bed outside of Tempe Town lake, and several miles of reclaimed habitat in south Phoenix. Navigation on this river is questionable at best like most rivers in AZ that have been dammed to provide reservoirs.
When we measure water in our washes, streams and rivers we do it in cfs (cubic feet per second) 
The joys of flash floods and the desert.
