Compute and plot problems about water resources in Excel file
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hw10_prob2.pdf
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Homework No. 10 -- Problem 2 -- Solution
1. Watershed Information
Watershed Drainage Area, Ad (km 2 ) = 240
2. Observed Flood Hydrograph, Base Flow Separation, Direct Runoff Hydrograph Derivation, and Numerical Integration
Incremental
Flood Direct Runoff Direct Runoff
Elapsed Time, ti Time Increment, Dti Hydrograph, Qi Hydrograph, QRi 1
Volume, DVRi 2
Direct Runoff
Date and Time (hours) (hours) (m 3 /sec) (m
3 /sec) (m
3 ) Index, i
3
2/16/2014 0:00 0 5 1.29 N/A N/A N/A
2/16/2014 5:00 5 5 1.25 N/A N/A N/A
2/16/2014 10:00 10 5 1.10 0.01 33,660 1
2/16/2014 15:00 15 5 4.82 3.73 127,440 2
2/16/2014 20:00 20 5 11.52 10.43 219,060 3
2/17/2014 1:00 25 5 15.00 13.91 267,750 4
2/17/2014 6:00 30 5 16.93 15.84 266,040 5
2/17/2014 11:00 35 5 14.81 13.72 223,650 6
2/17/2014 16:00 40 5 12.22 11.13 182,790 7
2/17/2014 21:00 45 5 10.27 9.18 149,040 8
2/18/2014 2:00 50 5 8.47 7.38 115,560 9
2/18/2014 7:00 55 5 6.55 5.46 86,670 10
2/18/2014 12:00 60 5 5.26 4.17 63,090 11
2/18/2014 17:00 65 5 3.93 2.84 39,240 12
2/18/2014 22:00 70 5 2.61 1.52 20,790 13
2/19/2014 3:00 75 5 1.88 0.79 7,110 14 n-1
2/19/2014 8:00 80 5 1.09 0.00 N/A 15 n
2/19/2014 13:00 85 5 0.62 N/A N/A N/A
2/19/2014 18:00 90 N/A 0.54 N/A N/A N/A
Total
Base Direct Runoff
Flow, QB (m 3 /sec)
4 = 1.09 Volume, VR (m
3 )
5 = 1,801,890
Notes: 1 Direct Runoff Hydrograph Ordinates, QRi = Qi - QB
2 Trapezoidal rule for numerical integration, DVRi = 1/2(QRi+QRi+1)Dti
3 Total number of direct runoff hydrograph ordinates, n = 15
4 QB = base flow at time t1 , where direct runoff begins
5 Total Direct Runoff Volume, VR = SDVRi , summation from i = 1 to i = n-1
3. Effective Rainfall Depth
Effective Rainfall Depth, R = total direct runoff volume, VR, in equivalent depth of rainfall uniformly spread over the watershed drainage area, Ad
R = VR / Ad
R (cm) = 0.75
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D is
c h
a rg
e (
m 3 /s
e c )
Time (hours)
Flood Hydrograph
Base Flow, QB =1.09 m 3/sec
Horizontal Base Flow Separation Line
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D is
c h
a rg
e (
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e c
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Time (hours)
Direct Runoff Hydrograph Derivation
Flood Hydrograph
Direct Runoff Hydrograph
1.09 m3/sec
