Please make your writing clear Hydrograph Analysis Exercise 2.2 The ordinates of a hydrograph at a section of a stream having a drainage area of 250 km2 are given below. Prepare the direct runoff hydrograph after separating the base flow Determine the equivalent depth of runoff 10 15 20 25 30 35 45 Time 1.37 1.25 1.12 5.00 12.00 15.60 17.15 14.40 12.50 10.70 Flow (m3/s) 55 60 65 70 75 85 90 95 Time Flow 8.80 6.80 5.50 4.10 2.75 2.00 1.20 0.65 0.60 0.56 (m3/s) Solution total area = 250km 2 = 250 x10 6 m 2 total flow = Q = 1.37 + 1.25+ 1.12 + 5 + 12 + 15.6+17.15+ 14.40+ 12.5 + 10.70 + 8.8 + 6.8 + 5.5 + 4.1 + 2.75+ 2 + 1.2+ 0.6+ 0.56 = 123.4 m 3 /s t = 1 hr = 3600 s Volume of direct runoff = V DRH = 123.4 x t = 123.4 x 3600 = 444240 m 3 V DRH in equvivalent units of depth =Â Â V DRH / area = 444240/ 250 x 10 6 equvivalent units of depth = 0.0018 m = 1.8 mm .