Tillage Strategies to Control Blowing Dust and PM10 Emissions from Williston Reservoir Beaches in British Columbia.

Williston Reservoir in northern British Columbia was created when BC Hydro constructed Bennett Dam on the Peace River in 1968 to generate hydroelectric power. Williston Reservoir is the largest body of freshwater in British Columbia with a surface area of 1775 km² and a shoreline of 1770 km.  The First Nation Tsay Keh band was forced to relocate to the north end of the reservoir as a result of the water impoundment.  When reservoir levels are at low pool in the spring, 10,000 ha of beach is exposed.  High winds of > 20 km/h cause dust storms from exposed beaches that impacts visibility and air quality in Tsay Key village.  With funding and coordination by BC Hydro, we conducted a comprehensive 3-yr field research project to evaluate methods to control blowing dust with various tillage practices.  The basic tactic for the tillage is to bring silt-clay soil from the subsurface to the surface to provide durable roughness. The main tillage study covered 75 hectares of land.  Measurements included sand transport on the tilled versus check treatments using BSNE traps, detailed GPS mapping of sand transport into the tilled treatment from the check borders, surface roughness, and measurement of PM₁₀ concentrations with E-Samplers. These measurements were obtained after every wind storm.  A separate tillage spacing experiment, using both twisted-point chisel and lister implements, was conducted to evaluate the comparative effectiveness of the implements and determine whether the entire beach area needs to be tilled to control blowing dust or if alternating strips of tilled and non-tilled ground would be adequate.  Results show that when there is silt or clay within 30 cm of the soil surface, tillage will produce a rough and stable soil surface. We know from our experiences that, to minimize blowing dust from Williston Reservoir, as much beach area as feasible should be tilled as any non-tilled areas will serve as source areas of blowing dust.