Delineating Groundwater Flow Paths in the Opabin Highlands, Yoho National Park, British Columbia

The Opabin Highlands is a hanging valley that is representative of the headwaters of many alpine river systems in the Rocky Mountains. Understanding the groundwater system is critical to understanding the timing of water release and the late season stream flow, especially given changing precipitation patterns expected with climate change. Water inputs to the Opabin Highlands are from snowmelt, glacier melt and summer rainfall. A moraine complex below the small glacier appears constructed of a moraine from a later advance overriding a moraine of an earlier advance. Resistivity and GPR images suggest the upper moraine may be cored with remnant basal ice or permafrost, while the lower moraine appears ice free. The source of the main stream in the valley is a spring that originates at the toe of the moraine complex. Water chemistry indicates that the spring is a mixture of more than one water source, with water chemistry in a small tarn and Opabin Lake being similar to one source. The tarn and Opabin Lake have no surface water inflows or outflows, and are thought to be connected to the groundwater system. Electrical resistivity imaging indicates that groundwater is flowing in discrete zones into and out of the tarn and into Opabin Lake, as well as up-valley of the springs. The cause of the channelling is unknown, but the location of one of the imaged channels is near the location of a tentatively mapped bedrock fault. The current hydrological model will be further constrained in the summer of 2008. Additional geophysical surveys will be conducted to test the groundwater channelling hypothesis and additional seismic refraction surveys used to verify the existence of ice within the upper moraine.