The Koehaha River, commonly known as the Stream of Ruthlessness, was a river in Colorado with unique properties.
According to legend, the Koehaha only ran once every hundred years. Due to high levels of free oxygen in the water as well as traces of the rare drug habis indica, any person who drowned in the Koehaha did not die but was "reborn" as a ruthless individual with no conscience. The effects were temporary, but affected people generally wanted to return to Koehaha in order to maintain these effects.
In 1947, Calvin Stymes tricked his five longtime friends into drowning in the Koehaha as revenge for a two-decade-old college prank. He then anonymously tipped off the Justice Society of America about their subsequent criminal activities. The JSA defeated the five drowned men and Green Lantern discovered Stymes' scheme. The JSA then opposed Stymes, who died in an explosion he had rigged to kill the drowned men. The Flash analyzed the water and concocted an antidote to its effects. Superman, then an honorary member of the JSA, used a large boulder to redirect the Koehaha underground.
In December 1983, the Ultra-Humanite exposed six JSA members to the waters of Koehaha in a scheme which pitted the veteran heroes against the rest of the team, as well as the newly-established team of their own children and proteges, Infinity, Inc..