HR: 0830h
AN: H51C-1044    [PDF]
TI: When Good Tracers Go Bad: Tracer-dilution Sausage Recipes Revealed
AU: * Runkel, R L
EM: runkel@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center PO Box 25046, MS 415, Denver, CO 80225
AU: Kimball, B A
EM: bkimball@usgs.gov
AF: U/S. Geological Survey, 2329 W Orton Cir, West Valley, UT 84119
AU: Walton-Day, K
EM: kwaltond@usgs.gov
AF: U.S. Geological Survey, Denver Federal Center PO Box 25046, MS 415, Denver, CO 80225
AU: Verplanck, P L
EM: plv@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Suite E-127, Boulder, CO 80303
AB: Theoretical development of the tracer-dilution technique for estimating streamflow is deceptively simple. Given a constant injection rate and concentration, streamflow is given by the simple ratio of injectate flux and observed tracer concentration. Practical application of the technique at the small-watershed scale is complicated by a number of factors, however, and streamflow estimates are often based on variations of the basic tracer-dilution formula. Case studies illustrate two non-ideal situations that can arise in the field: (1) the presence of losing reaches,and (2) failure to obtain a steady-state plateau. In the first case study, spatial tracer concentrations in the lower part of a study reach were nominally constant for more than 1500 meters. The spatially constant profile indicates that the 1500-meter subreach was either subject to a uniform flow field or a loss of flow. Conventional velocity-area discharge measurements coincident with the tracer experiment show a significant loss of flow within the subreach. Tracer-dilution estimates of streamflow were therefore adjusted to reflect the flow loss. An alternate form of the tracer-dilution equation was then used to estimate flows downstream of the losing subreach. In the second case study, the tracer concentrations did not reach a steady-state plateau during the injection period. Stream samples collected immediately before the end of the injection were used in conjunction with velocity-area discharge measurements to determine the flow field. Streamflow at approximately 1 kilometer downstream of the injection was first set equal to the velocity-area measurement. Using this streamflow estimate as a starting point, streamflow at the remaining downstream sites was estimated using an alternate form of the tracer-dilution equation and the site-to-site variations in tracer concentration. Streamflow estimates for sites upstream of 1 kilometer were obtained in a similar manner.
UR: http://co.water.usgs.gov/toxics
DE: 1806 Chemistry of fresh water
DE: 1836 Hydrologic budget (1655)
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting