An irrigation scheme is fed from a river via a diversion channel. The irrigation channel is 2 m wide and is constructed of concrete with an estimated value of 0.019 for the Manning n. The bed slope is 0.0025.

The discharge into the channel is controlled by a vertical sluice gate (Cc = 0.61). The depth upstream of the gate is a constant 2.8 m, and the maximum discharge is 10 m3/s.

The designer of the gate has prepared a rating curve for the sluice gate (YG vs Q) for free flowing conditions as shown below in the table.

The issue is that the designer has not considered those cases where the gate may be drowned by the hydraulic jump downstream of the gate. The depth on the downstream side of the gate is equal to the normal flow depth.

Independently you have determined the normal flow depths over the operating range of discharges, which is also included in the table below.

(a) Determine at what discharge the gate changes from freely flowing to submergedconditions (to the nearest m3/s)

(b) Calculate the new gate opening (YG) for those discharges for where the gate issubmerged by the depth downstream of the gate.

(c) Plot the new rating curve (alter the part where gate is submerged)