Added 2021-08-14
This drive is so interesting! Water tunnels literally are routed underground and the water comes billowing out at various points above ground... it is unnerving and a very interesting engineering feat.
The road can be muddy and rough in some places so you might want to take a higher-clearance vehicle but you should be fine with whatever if you drive carefully.
Turn north off of Sun Canyon Road onto Castle Reef Road which will then turn into Pishkun Road after a couple of minutes (look at the map so you know which dirt roads to not turn onto).
The canal may be empty depending on the time of year (we went in April and it was empty).
This is just one more cool thing to do in this beautiful area.