Assessing the impact of a mining project requires knowledge of the water balance. Study of stream flow variation over the open water season can be readily accomplished with a variety of conventional methods, but understanding the behaviour of streams in winter low flow is hampered by uncertainty. Knowledge of absolute low flow can be vital in anticipating environmental effects of mining projects and describing the possible effects of climate change.
Streamflow has been measured using variations of dye dilution and tracers of all kinds for many years, but these were always cumbersome. Recently, advances in instrumentation have allowed a variation of the salt dilution method to be a practical method for streamflow measurement.
Geoff Kite of the National Hydrology Research Institute (NHRI) has experimented with a streamflow measurement technique using injection of a salt slug and calculation of flow based on the conservation of mass. The method is described in re 'Measuring glacier outflows using a computerized conductivity system', Journal of Glaciology, Vol. 40, No. 134, 1994 (attached as Appendix A), and 'Computerized Streamflow Measurement Using Slug Injection', Hydrological Processes, Vol. 7, 227-223 (1993). A software program converts the conductivity readings to flow, with a computer coupled to the conductivity meter through digital/analog converter.
This report summarizes a project undertaken by Laberge Environmental Services for the Mining Environment Research Group (MERG) during the late winter low flow period of 1998/1999. The Salt Slug Injection method of stream flow monitoring as described by Kite was tested to determine its applicability to Yukon mining monitoring situations under late winter low flow conditions. Transfer of technology to user groups was accomplished through this report and accompanying information pamphlet, a workshop, and direct training experience.
