Chapter 2. Moving Down the Mountain Stream
It was the unusual warmth that drew us out of our tents the next morning. We were all used to donning layered clothing, hats and boots in early mountain mornings before heading to the fire pit to make coffee and warm up for breakfast. But this morning was different with a pleasant temperature of about 10C and a light breeze to keep the mosquitoes in the bushes. The clear blue Alberta sky seen above the pink-tinged mountain peaks surrounding the lake promised a fine day of hiking ahead. No rain (or snow!) was likely, unlike the June downpours our hiking group had waded through the previous month; happily that part of the hydrologic cycle would be absent. Instead, the hydrology we were interested in involved the surface waters of the lake and the Elbow River, and the contents of our water bottles.
Mountain-sourced rivers in this region, like the Elbow, get most of their water directly from mountain snowpack melt (spring and summer) and from precipitation in the high foothills (May through July), with the remainder coming from groundwater, other snowmelt and alpine glaciers. Here in the rocky upper Elbow much of the meltwater and precipitation flows directly into the river, but below in the subalpine and boreal zones, where annual precipitation is the highest in the watershed, a considerable amount is intercepted by coniferous forests, absorbed by their dense foliage and the significant water-holding capacity of the needles. The remainder falls through to the ground surface where it soaks into the forest soil.
The aspen forests and grasslands lower in the watershed intercept less than the coniferous trees, but still provide the vegetative cover which is critical to the health of the watershed. Vegetation protects the soil from direct raindrop impact, holds soil moisture with its root structure and increases the permeability of the soil, thus reducing runoff and erosion. In urban areas within the watershed, however, like in the City of Calgary, much less precipitation is captured and stored, since more runs directly off into the river over impermeable pavements and roofs. Eventually though, no matter what its source, the Elbow’s water is on a long trip to the Atlantic Ocean — an eastward journey through the Bow, South Saskatchewan and Saskatchewan rivers, Lake Winnipeg, the Nelson River and Hudson Bay.