HOMS COMPONENT

MEASUREMENT OF DISCHARGE USING TRACERS

1.   Purpose and objectives

     To provide detailed theory and methodology on the performance of discharge measurements using tracer dilution techniques.

2.   Description

     The manual (Kilpatrick and Cobb, 1985) describes the slug injection and constant rate injection methods of performing tracer dilution measurements. Emphasis is on the use of fluorescent dyes as tracers for performing such measurements. The tracer velocity method is also briefly discussed. The methods described are particularly appropriate for small stream, canals, and pipes where (1) turbulence is excessive, (2) cross- sectional areas or velocities are indeterminate or changing, (3) moving 
rocks and debris may damage instruments placed in the flow, (4) the flow is unsteady, and (5) the measuring site is physically inaccessible or unsafe.

3.   Input

     A measured amount of tracer is injected into the flow to be measured.

4.   Output

     The discharge is obtained by measuring the dilution produced.

5.   Operational requirements and restrictions

     Dyes should not be injected into streams in quantities that would result in dye concentrations exceeding 10 micrograms/litre at water-user withdrawal points. Regulations in different countries may prohibit use of particular dyes.

     Equipment needed: Fluorometer to measure rhodamine WT dye concentrations and a constant injection device.

     Most of the needed guidance is provided in the manual, however, some knowledge of hydraulics is beneficial to determine the proper sampling technique.

6.   Form of presentation

     Manual, written in English, is available (Kilpatrick and Cobb, 1985).

7.   Operational experience

     Extensive use within the United States.

8.   Originator and technical support

     U.S. Geological Survey, Office of Surface Water, Reston, Virginia, USA.

9.   Availability

     From the HOMS National Reference Centre for the United States.

10.  Conditions on use

     The manual is available free of charge.

Reference:

Kilpatrick, F. A. and Cobb, E. D., 1985, Measurement of discharge using tracers: U.S. Geological Survey, Techniques of Water Resources Investigations, Book 3, Chapter A16, 52 pp.

Last updated: 29 NOV 94)
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