In answer to Ethereal_Reality regarding his post on the small structure and channel in Elysian Park on page 606. This appears to be a part of the old Buena Vista Reservoir in Elysian Park. The pipe may be one of the early wooden pipes, terminating at a flow control gate emptying into an open water channel.
Part of this channel may be seen on Google Maps satellite view of Elysian Reservoir. Locate the parked white pickup and trailer at the midpoint of the reservoir and follow along the edge towards Grand View Avenue. The channel comes into view at the corner of the reservoir.
See:
http://waterandpower.org/museum/Wate...s_Angeles.html
Additional research reveals that I may be wrong about the channel connecting to the reservoir. The picture is explained here:
http://lashp.remap.ucla.edu/visual/m...g2_itemId=3082
Cheers, Jack