The mass curve of an isolated storm in a 500 ha watershed is as follows: Time (hr) 4 6. 8 10 12 14 16 18 Cumulative 0.8 2.6 2.8 4.1 7.3 10.8 11.8 12.4 12.6 rainfall (cm) If the direct runoff produced by the storm is measured at the outlet of the watershed a • Determine the total ER and infiltration in cm. • Estimate the d-index of the storm and the duration of the rainfall excess. • Plot the hyetograph showing the d-index. • Plot the ER.

A catchment has the Horton infiltration parameters: fo= 150 mm/h, fc = 50 mm/h, and k = 3 min¹. The design storm is given below. Estimate the time when ponding begins. Interval (min) Average rainfall (mm/hr) 20 40 80 170 90 20 0-10 10-20 20-30 30-40 40-50 50-60

Net Storm Rainfall Example 2-1 Rain falls as shown in the rainfall hyetograph (intensity Vs. time) in Fig. E2-1 (a). The o index for the Storm is 0.5 in./hr and is constant over 5 hr. Plot the net rainfall on the hydrograph (flow vs. time) given in Fig. E2-1 (a). Determine the total volume of runoff and the watershed area. 1cfs = 1.008 ac-in/hr 2.0 1.5 1.0 0.5 1 3. 4 Time (hr) 700 600 500 400 300 200 100 4 8 12 16 20 24 Time (hr) Time (hr) Q (cfs) Volume (cfs-hr) 0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 24-26 16 Q (cfs) iT (in./hr)

Q2. Two storms having duration of 4-hv and 2.hr respectively. If the rainfall excess values for the two storms were 2cm f 3cm respectively occurs Successive calculate the resulting direct runoff hydrographif the 2-hr UH For the Catchment is given below Time hr 2 4 G 10 12 14 16 18 2hr UH 25 50 75 125 100 60 20