A water detention system for detaining storm water having a side wall and a bottom floor; an inlet conduit for ingress of storm water; and a water discharging assembly, which includes a siphon, configured to pass storm water there through; and an outlet conduit for egress of storm water from the water discharging assembly. The inlet and outlet conduits are disposed through the side wall of the water detention system. A water discharging assembly for discharging storm water from a water detention system includes an outer enclosure; a first opening in the outer enclosure for ingress of water; a second opening in the outer enclosure for egress of water; and a siphon disposed within the outer enclosure; where, except of the first opening and the second opening, the outer enclosure is substantially fluid tight.