Happy Jacks is the first of 6 dams downstream from the source of the Tumut River. It captures spring snowmelt for diversion down the intake shaft into the Eucumbene -Tumut tunnel and into Lake Eucumbene. The flows of the Tumut and Happy Jacks Rivers usually pass through the
dam via open river outlet conduits in the base of the
dam. These are closed during high flows for diversion when the shaft control gates are open. With the shaft and conduits both closed the
dam will spill. The pondage is only likely to be seen by keen skiers or cyclists as it is 9 km from the main road. See You Tube for spill March 2012.