L
Lisa
NCEES Sample exam - problem 508 - Water Resources and Environmental
I'm having some trouble understanding the solution to this problem. Can anyone help?
A rain event has an intensity of 1.5 in/hr for the first hour followed by 0.7in/hr for the second hour. The 1-hour unit hydrograph for the watershed is given as:
Q (cfs/in) 0.5, 1.2, 0.4
T (hours) 1, 2, 3
Neglecting infiltration, the discharge (cfs) from the watershed during the second hour is most nearly:
(A) 2.64
(B) 2.15
© 1.44
(D) 1.20
From the solution:
Q = effective rainfall x unit hydrograph ordinate (runoff/inch of rainfall)
Flow during the second hour: Q = 1.5 x 1.2 + 0.7 x 0.5 = 1.8 + 0.35 = 2.15 cfs
I'm having some trouble understanding the solution to this problem. Can anyone help?
A rain event has an intensity of 1.5 in/hr for the first hour followed by 0.7in/hr for the second hour. The 1-hour unit hydrograph for the watershed is given as:
Q (cfs/in) 0.5, 1.2, 0.4
T (hours) 1, 2, 3
Neglecting infiltration, the discharge (cfs) from the watershed during the second hour is most nearly:
(A) 2.64
(B) 2.15
© 1.44
(D) 1.20
From the solution:
Q = effective rainfall x unit hydrograph ordinate (runoff/inch of rainfall)
Flow during the second hour: Q = 1.5 x 1.2 + 0.7 x 0.5 = 1.8 + 0.35 = 2.15 cfs