This research determines the cause of this scatter by investigating the components of the water budget over a series of exposed bedrock plots. This work is important because it is the exposed bedrock ridges that supply much of the source water to lower slopes crucial for maintaining hydrological connections between shield uplands and lowlands. Precipitation, runoff, evaporation, infiltration and storage capacity were measured over exposed bedrock plots near Yellowknife, Northwest Territories over the summer of 1999. Two plots contained only exposed bedrock and two had portions of soil cover in bedrock depressions. Surface runoff increases with rainfall volume, but intensity is important as high intensity precipitation rates can exceed infiltration rates.
Longer events allow for more losses to the air and subsurface.
Storms in June and July experience less runoff and infiltration as much of the rainfall evaporates, while storms of similar magnitude in late August and September when evaporation rates are lower, have more runoff and infiltration. Infiltration increases with fracture density. Preferential surface runoff along fractures results in concentrated flow into overburden along the soil bedrock contact. The size distribution of fractures strongly affects infiltration rates in individual plots. Soil cover slows the movement of water, enhancing evaporation and infiltration but reducing runoff.