ASTM: D5613: Travel Time
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Official Method Name
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Standard Test Method for Open-Channel Measurement of Time of Travel Using Dye Tracers |
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Current Revision
| Reapproved 1998. Current edition approved Sept. 15, 1994. Published November 1994. |
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Media
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WATER |
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Instrumentation
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Dye injection, Fluorimetric Measurement |
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Method Subcategory
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Physical |
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Method Source
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Citation
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Brief Method Summary
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Dye tracers injected into a stream are assumed to behave in the same manner as the water molecules themselves. A measure of the longitudinal movement of a tracer along a given streamline will be a measure of the movement of an element of fluid in the stream and of its dispersion characteristics for that streamline. The initial planning of a dye tracer time-of-travel study involves the estimation of stream velocities and the required tracer injection volume. The information necessary for these estimations is obtained by reviewing historical flow data and topographic maps and by making a reconnaissance of the proposed study reach. The time-of-travel for a given flow is determined by observing the passage of a slug-injected dye tracer cloud at previously identified locations along the study reach. The dye cloud response curve is defined at each reach location (study site) by measuring the dye concentration in collected water samples and noting the time that each sample was collected since the tracer injection. After tracer studies have been conducted at two or more flow durations on the study reach, estimation of the time-of-travel and dispersion of a solute can be made at any flow between those studied. Tracer studies are typically performed at 40 to 90 % flow duration ranges. |
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Scope and Application
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This test method covers a means of measuring the time-of-travel of water and waterborne solutes by the use of dye tracers and tracing techniques. This test method is similar to methods developed by the U.S. Geological Survey and described in other referenced documents. This test method describes the dye tracers, measuring equipment used, and field and laboratory procedures customarily used. |
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Applicable Concentration Range
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None. |
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Interferences
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Natural water may exhibit background fluorescence that is not the result of a fluorescent dye tracer. This background fluorescence may result from scattered light, fluorescence of natural materials or pollutants, or other causes. The fluorescence of Rhodamine WT is stable in solutions having a pH in the range from 5 to 10, which is within the range of most streams. Rhodamine WT fluorescent decreases when in solutions having a pH below 5. Dye tracer fluorescence may be quenched by the action of other chemicals in the streamwater. The quenching agent may cause any of the following to occur: absorption of exciting light, absorption of light emitted by the dye, degradation of the excited-state energy, and chemically changing the fluorescent compound of the dye tracer. The permanent reduction of Rhodamine dye tracer fluorescence can be caused by photochemical decay as a result of exposure to sunlight. Sunlight degradation half-lives for the dye at the water surface to a depth of 0.03 ft ranged from 15 to 30 days at 30o North latitude, depending on the season of the year. The degradation half-lives ranged from 15 to 44 days at 40o North latitude, depending on the season of the year. The photochemical decay half-life increases with increased water depth and decreasing light intensity; it is therefore not a concern for most practical problems. |
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Quality Control Requirements
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Sample Handling
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Collect samples in accordance with Specification D 1192 and Practices D 3370. In general, select a minimum of three points laterally across each stream study site for sample collection. Select the points on the basis of cumulative discharge and flag or otherwise mark the location for repeated sampling. Use the same cumulative discharge points (streamlines) at all study sites along a stream reach. Table 1in the method is provided to assist in selecting sample point locations for even discharge increments. More than three sampling points are recommended for wide or shallow streams. Collect enough samples at each sample point at a study site (30 to 40 samples) to define the shape of the tracer response curve. The samples must be taken at more frequent intervals from the leading edge through the peak tracer concentration due to the typical, skewed shape of a tracer response curve. Less frequent sample collection is common practice to the trailing edge of the response curve. Ideally, no more than 5 % of the dye mass, with a maximum of 10 % of the dye mass, passes a study site between samples. A minimum sample volume of 100 mL is required for collection. This will allow at least six to eight concentration determinations in most fluorometers using a 5 to 20-mL cuvette discrete sample holder. All samples should be collected and stored in glass containers since Rhodamine WT has an affinity for many plastics. The samples should also be stored in the dark to avoid photo reduction of the tracer's fluorescence. Plastic bottles can be used only for short-term storage. Plastic tubing used in pumping and flow-through systems are not a problem because the contact times are too short for significant sorption to occur. |
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Maximum Holding Time
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Relative Cost
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Greater than $400 |
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Sample Preparation Methods
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