186 IRRIGATION AND WATER RESOURCES ENGINEERING
5.9.5.2. Khanna’s Rigid Orifice Module This outlet is similar to an orifice semi-module. But, in addition, it has sloping shoots fixed in the roof block (Fig. 5.9). These shoots cause back flow and thus keep the outlet discharge constant. If the water level in the distributary is at or below its normal level, the outlet behaves like an orifice semi-module. But, when the water level in the distributary channel is above its normal level, the water level rises in chamber A, and enters the first sloping shoot. This causes back flow and dissipates additional energy. This maintains a constant discharge. The number of sloping shoots and their height above the normal level can vary to suit local requirements. The shoots are housed in a chamber to prevent them from being tampered with. If the shoots are blocked, the outlet continues to function as a semi-module.
