A productivity study on Smith Mountain Lake

Abstract

The rapid deterioration of the water quality in the upper end of the Roanoke River arm of Smith Mountain Lake has caused much concern. Eutrophic conditions have been established in this portion of the lake since 1965, when it was first brought to operating level.

A multiphase productivity study was conducted on Smith Mountain Lake and lower Leesville Lake during July, August and September of 1971. Parameters monitored in this study included oxygen, temperature, algae, bacteria, specific conductance, light and primary productivity. The effect of each of these parameters on the trophic levels in the reservoirs was studied.

The results of this investigation showed that the inflow of the nutrient rich Roanoke River had caused eutrophic conditions to develop on the upper reaches of Smith Mountain Lake. High suspended solids levels had greatly reduced light penetration, causing productivity to be limited in the uppermost portions of the lake.

Evaluation of the productivity potential of the hypolimnion of Smith Mountain Lake indicated that destratification would be detrimental to water quality. Stratification in Smith Mountain Lake was only slightly affected by the pump-back from lower Leesville Lake.

Equations were developed in this study for predicting the level of productivity from light extinction coefficients. These equations showed good correlation with observed levels of productivity in the lower half of Smith Mountain Lake.