A 6.0-hr storm rains on a 25.0 mi2 drainage watershed. Records from a stream gauging stations are shown in the table below.
t, (hr) Q, (ft 3/sec)
0 0
3 400
6 1300
9 2500
12 1700
15 1200
18 800
21 600
24 400
27 300
30 200
33 100
36 0
Total 9500
(a) construct the unit hydrograph for the 6.0-hr storm.
(b) Determine the runoff rate at t = 15.0 hr from a two storm system if the first storm drops 2.0-inches starting at t = 0, and the second storm drops 5.0-incheds starting at t = 12.0 hrs.