Dilution Gauging (Gulp Injection) Example Worksheet

Dilution Gauging Example Worksheet

Dilution Gauging (Gulp Injection) Worksheet
Date: 4 February 1995	Time:3:30 pm	Operator: NAC/LS/NRT

Site: White Scar, above main fall (40 m mixing reach)

Meter Units: µScm^-1

Background conductivity: 125 µScm^-1

C0: 88 mgl^-1

Tracer volume (V): 20 l (20 or 40 litres)

Tracer conc (C1): 45,000 mg l^-1

Note: 900 g in 20 l is 45,000 mg l^-1

Time
(mins)

Reading
(µScm^-1)

Concentration
C2 (mgl^-1)

C2 - C0
(mgl^-1)

0	125	88	0
0.5	125	88	0
1	125	88	0
1.5	125	88	0
2	250	175	87
2.5	417	292	204
3	369	258	170
3.5	274	192	104
4	202	141	53
4.5	163	114	26
5	145	102	14
5.5	135	95	7
6	130	91	3
6.5	128	90	2
7	127	89	1
7.5	126	88	0
8	126	88	0

Note: This example and your field test is an illustration only. An accurate dilution gauging would require: (i) a more precise and accurate conductivity-salt calibration, (ii) a time increment of at least 0.25 mins, rather than the 0.5 mins presented here, and (iii) more precise conversions above.

Notice the long recession in the C2-CO values. This results from the tracer mixing into the large body of slow moving water (a ‘dead-zone’) just below the insurgent waterfall.

The integral of (C2-C0) is:

The_integral_of_(C2-C0)

The discharge is:

The_discharge

Dr. Nick A. Chappell <N.Chappell@lancaster.ac.uk>