Understanding the factors associated with long-term reconstructed turbidity in Lake Diefenbaker from Landsat-imagery.

Abstract Turbidity affects a variety of aquatic ecosystem processes. Turbidity events are dominated by suspended sediment in many systems. High levels of suspended sediment in lakes can occur during periods of high inflows from turbid tributaries or suspension of sediment from lake beds. This study reconstructed historic turbidity levels using Landsat-imagery on Lake Diefenbaker (LD), a large river-reservoir constructed in the late 1960's on the naturally turbid South Saskatchewan River (SSR). We examined the factors that were associated with it. Reconstructed turbidity levels, from Landsat-images, were similar to actual turbidity. The SSR flow and wind speed explained 64%, 54% and 69% of the variability in estimated turbidity levels at the riverine zone, the transition zone and the entire reservoir, respectively. The decrease in estimated turbidity from June to October and down the length of the reservoir is likely associated with the decline in the SSR flow and the settling of suspended sediments. The relationship between estimated turbidity and wind speed may be associated with the re-suspension of bottom sediment at the upper reach of LD. Wind speed and direction were related to estimated turbidity at the lacustrine zone (r2adj = 0.19, P