>Unless the stormwater system has been upgraded and the sewer system tightened up, I am guessing that not much has changed with respect to flows to Hyperion for example during storm events.
Both have been very upgraded. There are no sewage spills anymore, because Hyperion is not being inundated. I believe this was as a result of EPA action.
>The questiion also remains what is being done with the stormwater that does manage to stay separate from the sewer: is any recovered?
Virtually none. The Los Angeles River just flows into the ocean, either near Marina del Rey or Long Beach.
Contrast that with the San Gabriel River, to the east. Virtually every drop is captured and infiltrated into groundwater.
Thankfully, this situation is now being viewed as an opportunity:
http://www.lastormwater.org/blog/2012/05/creating-a-lasting-impression/
