Question

ull peal - OX Share Comments AutoSave Off 2 0 - Quiz 3_2 (1) - Compatibility Mode - Word Search File Home Insert Design Layout References Mailings Review View Help Times New Rom 12 AA Aa A Eva EE 7 AL | Paste BI U veb xx? APA SIE DI La АаВЬСc) АаВЬСcІ Аавьсс Аавьссс Аав — Heading 1 1 Normal 1 No Spac.. Heading 2 Title sinca nasce Aabe Find Sc Replace h Select Dictate Sensitivity Editor Clipboard Font Paragraph Styles Editing Voice Sensitivity Editor | A watershed has the time-area relationship between its sub-basins and the outlet as shown in Table 1. Rainfall was measured using a standard non-recording rain gauge and given in Table 2. The o index of 0.5 in/hr and a depression storage of 0.3 inches can be assumed. a) Calculate the direct runoff hydrograph (in cfs) for this watershed using Time-Area method. b) Draw the DRO hydrograph and the excess rainfall hyetograph on the same plot. c) Estimate the peak flow, lag-time, time-base and time of rise. Table 1: Time-area relation Table 2: Measured rainfall Time Area (ac) Time (hr) 0:00 0:30 1:00 1:30 2:00 2:30 3:00 (ht:min) 250 Rainfall 0 0.4 0.8 3.2 4.2 5.2 (in.) 198.92 180 70 1 acre = 43560 AP 1 in = 25.4 mm Page 2 of 3 321 words & English (United States) Focus 3 -— H - + 100%

Answer 1

a)

Time	Area	Incremental area	Cumulative rainfall	Rainfall	Losses = $\phi _{i}\Delta t +$ depression storage	Effective rainfall	Hyetograph ordinates	Runoff generated by effective rainfall of 0.65 in	Runoff generated by effective rainfall of 0.45 in	Total hydrograph ordinates
0	0	0	0							0
0.5	250		0.4	0		0	0
1	250	250	0.8	0.4	0.55	0	0	0		0
1.5	198.92		2	1.2	0.55	0.65	1.3
2	198.92	448.92	3.2	1.2	0.55	0.65	1.3	327.7083	0	327.7083
2.5	180		4.2	1	0.55	0.45	0.9
3	180	628.92	5.2	1	0.55	0.45	0.9	260.7509	226.875	487.6259
3.5	70
4	70	698.92						235.95	180.5199	416.4699
4.5
5								91.7583	163.35	255.1083
5.5
6									63.525	63.525
6.5
7									0	0

Discharge Intensity 4 5 6 6.5 Time

c) Peak flow = 487.6259 cfs

Lag time= Difference in peak of DRH and hyetograph = 3 - 1.5 = 1.5 hour

Peak of Hyetograph = 1.5 hr

Peak of DRH = 3 hr

Time of rise = 3hour