McGillivary Falls Self-Guiding Trail

This particular type of drainage system and its associated characteristics are found throughout Whiteshell Provincial Park. The controlling factor in this pattern is the erosion-resistant bedrock of the area. The pattern is known as deranged drainage and indicates the earlier activity of glaciers.

1. The existence of McGillivray Falls indicates that this stream is relatively young in terms of geological time, and that this is a primitive drainage system. After many thousands of years, these waterfalls will erode down to a smooth channel.
2. The rock face on the other side of the falls has no water-line or other marks of erosion by the stream. This is because the stream follows a natural channel cut in the rock by the movement of glaciers, which melted away about 12,000 years ago. Had there been no natural depression, the stream would not be flowing here, as the granite rock is very resistant to water erosion.
3. Beavers bring about changes in drainage by building dams with branches and mud. The dams create reservoirs in the stream, resulting in lower but more constant flow downstream. For more information on the beaver visit the Picket Creek Trail and the Whiteshell Museum at Nutimik Lake in the north end of the park.
   
   
   
4. From this viewpoint you can see the natural depression in the bedrock. This depression has been partially filled with material carried down by the stream and washed in from all sides. It has taken thousands of years to reach this stage.
5. You are standing on the remains of a dam built many years ago to hold back spring runoff and maintain a higher waterlevel in McGillivray Lake. However, some years ago part of the dam was removed to restore natural flow of the stream.
6. McGillivary Lake and the bog through which the stream flows can be seen from this ridge. Changes in the vegetation to the left of the stream indicate the amount of water in the soil at different elevations.
   
   
   
7. The several varieties of trees on this rocky slope indicate the varying amounts of soil and water present. Jack Pine grows at the top of the ridge where there is little soil and water runs off quickly. Dry ridges such as this are extremely susceptible to fire in dry seasons. Where there is water draining down the slope and more soil, birch, aspen and white spruce flourish. Where water accumulates at the bottom, only bog plants and black spruce grow.
   
   
   
8. This is McGillivray Lake. It is a typical lake of the Precambrian Shield with a maximum depth of about three metres. The water is rich in nutrients, algae and naturally occurring humic acid, giving the water its brownish tinge. The lake is fed by two small streams and by run-off water. Lakes such as this, with a small volume and a slow flushing action, are extremely sensitive to environmental pollutants.
9. This black spruce bog is different in origin from the one seen earlier, beside the stream. This bog is completely enclosed by rock ridges. Water accumulates in this depression in the bedrock because it cannot drain away. Evaporation is minimal because the water is held within the spongy sphagnum moss covering the bog. A very moist habitat is thus created on what would otherwise be dry rock.
10. You are now on top of a granite ridge which the trail follows to the parking lot. Here the environment is dry because water drains away quickly. Ridges such as this are usually dominated by jack pine, one of the few tree species that can grow under these austere conditions.