A continuous dye injection system for estimating discharge in snow-choked streams

Abstract

A simple method is presented which demonstrates the use of continuously injected Rhodamine WT dye to provide automated around-the-clock estimates of flow during the spring breakup. Dye of a known concentration is injected at a constant rate upstream from a sampling point, and the dilution of the dye in the sampled downstream water is a measure of discharge. Field trials conducted in and around Inuvik, Northwest Territories in two small snow-choked streams during spring breakup of 1995 to 1999 suggest that some dye is adsorbed to suspended sediment in the stream channel, resulting in an overestimate of discharge. However, there is still a strong linear relationship between the discharge as estimated by the dye method and that determined by conventional current metering. Correcting the dye values by a linear regression equation line results in a reasonable estimate of streamflow. This method's most promising application is in the monitoring of small basins where much of the annual discharge occurs during the spring melt. Given the occurrence of rapid changes in discharge in these basins due to both diurnal variations in snowmelt and changing runoff source area, and the excessive manpower required to carry out a sufficient number of current meterings needed to properly observe this changing discharge, the dye dilution method often provides a more accurate estimate of discharge. © 2004 Regents of the University of Colorado.