Determine the headwater depth of a 1000mm(high) by 1500(wide) concrete box culvert operating under outlet control with a stream flow of 3.0m3/s. The culvert is 50m long, Ke=0.5 and on a slope of 0.25%. The tail water depth is 1.1m. What will the headwater depth be if tail water is reduced by 0.8m?