Dye tracing in forested karst terrain: A case study on Vancouver Island, British Columbia

This paper presents the findings of a groundwater dye tracing study that was carried out in the Glory'Ole Cave/Karst Management Area (GCMA) of Northern Vancouver Island, British Columbia. The objectives of the project were to delineate the groundwater flow paths and recharge areas of the GCMA, and to demonstrate how this information could be used to assist in forest management. Four fluorescent dyes (fluorescein, rhodamine WT, eosine, and pyranine) were simultaneously injected into flowing water at four different locations; three sinking streams and a surface stream. Charcoal samplers and grab water samples were taken from springs and streams at lower elevations and analyzed for the presence of dyes. All four dye traces were detected at the Tsulton Rising, the principal discharge point for groundwater flow in the GCMA. Most of the non-karst recharge areas upslope of the GCMA contribute to the groundwater discharge at Tsulton Rising. Careful forest management planning and prescriptions are required in these recharge areas to protect water quality and quantity.