Lecture 6

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Stream Discharge

Fetter 3.6
Method for computing stream discharge.
Measured at least 25 verticals across the stream.

Methods diagram

 

 

Velocity distribution in a stream channel

Average velocity is 0.6 below surface of water.
Slower velocity on channel edges (friction).
Faster velocity at surface of water in center of channel.

 

 

 

Methods diagram

Definition sketch of midsection method of computing cross-section area for discharge

measurements.

 

 

 

Stage-discharge diagram

 
Develop a stage discharge relationship for a gaging station.
Therefore, one can get discharge from knowing river stage.
Relationship is dependent on the irregular geometry of the channel.

Sample worksheet for calculating stream discharge

 
            VELOCITY    

Dist. from initial point

 

Width

 

Depth

Observ-ation depth

Revolut-ions

Time in sec-onds

At point

Mean in vertical

 

Area

 

Dis-charge
6 1.5 0              
9 3 .40 .6 10 40 .565   1.20 .68
12 3 .48 .6 15 50 .674   1.44 .97
15 3 .72 .6 7 42 .383   2.16 .83
18 3 .78 .6 7 40 .401   2.34 .94
21 2.5 .86 .6 15 40 .837   2.15 1.80
23 2 .96 .6 25 50 1.11   1.92 2.13
25 2 1.00 .6 20 41 1.08   2.00 2.16
27 1.75 1.08 .6 20 43 1.03   1.89 1.95
28.5 1.5 1.18 .6 15 46 .731   1.77 1.29
30 1.5 1.24 .6 30 45 1.47   1.86 2.73
31.5 1.5 1.34 .6 20 52 .858   2.01 1.72
33 1.5 1.48 .6 25 45 1.23   2.22 2.73
34.5 1.5 1.58 .6 25 45 1.23   2.37 2.92
36 1.5 1.50 .6 25 42 1.32   2.25 2.97
37.5 1.5 1.48 .6 25 40 1.38   2.22 3.06
39 1.5 1.50 .6 25 43 1.29   2.25 2.90
40.5 1.5 1.60 .6 20 50 .892   2.40 2.14
42 1.5 1.24 .6 25 41 1.35   1.86 2.51
43.5 1.5 1.30 .6 20 53 .843   1.95 1.64
45 1.5 1.20 .6 20 51 .875   1.80 1.58
46.5 1.5 1.00 .6 20 56 .799   1.50 1.20
48 1.75 .96 .6 20 58 .772   1.68 1.30
50 2.5 .40 .6 15 47 .716   1.00 .72
53 1.5 0              
                --- ---
--- ---             44.24 42.87
47 47                

 

Width of Sections:

 

  1. The width at the first section (station 6) is equal to 1/2 the distance between the first

    2. observation point (station 6) and the second observation point (station 9) .

     

  2. The width of the second section (station 9) is equal to 1/2 the distance between the

    3. preceding observation point (station 6) and the succeeding observation point

    (station 12) . This method is used up to the final section.

     

  3. The width of the last section (station 53) is equal to 1/2 the distance between the last

observation point (station 53) and the preceeding observation point (station 50) .

 

The sum of widths in column z should be equal to the width of the stream.

 

Stilling Well used to measure stream stage.

 

 

 

Typical bubble-gage installation for measuring stream stage.

 

 

 

Manometer assembly and gas-purge system used to measure stream stage.

 

 

 

The following is a hypothetical storm hydrograph for a stream.

 

 

 

 

 

 
Verde River at Clarkdale:
Drainage basin area = 3,503 mi 2
Datum - stream gage = 3,500 ft above mean sea level
River ~ 100 ft wide.
See following graphs for discharge hydrograph of Verde River.
Hydrograph separation methods. (Fetter p.57)
Graphical methods for estimates.
Separate Baseflow & Runoff components.

 
1) Plot daily stream discharge dates vs. time.
2) Compute number of days after peak of Hydrograph when Baseflow returns.
N=A0.2 empirical
N = Number of days after peak.
A = Area of drainage basin contributing baseflow (mi2).

 

 

Figure 3.9

Figure 3.9 Hydrograph separation into overland-flow component and baseflow

component for a stream receiving Horton overland flow.

 

 

Verde River discharge near Clarkdale

1992-1993

 

Verde River discharge chart

 

 

 

 

Verde River baseflow distribution graphs

 

Distribution of baseflow for the Verde River at

 

a) Paulden (1965-78)

 

b) Clarkdale (1966-78)

 

c) Camp Verde (1935-45 and 1976-79)

 

 

 

Santa Cruz River location map

 

 

 

Hydrogeologic profile

 

Generalized longitudinal hydrogeologic profile of the Upper Santa Cruz River in Arizona.

Note areas where the Santa Cruz River gains water from and loses water to the Regional aquifer.

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