Richard B. Russell Dam and Reservoir: Potential Water Quality Effects of Initial Filling and Decomposition of Vegetation

摘要

Findings of a study to quantify and then evaluate the contribution of initial soil flooding and decomposition of vegetation to the water quality of the newly filled Richard B. Russell Lake are reported herein. Samples of soils and vegetation were taken from three areas representing the most predominant types of soil vegetation within the boundaries of the lake. Using controlled conditions in the laboratory, it was found that both soils and vegetation can release significant quantities of oxygen-consuming materials and plant nutrients. Soil samples had an oxygen demand large enough to cause strong depletion of dissolved oxygen fro mthe overlying water at 5 and 12.5 C, while samples held at 20 C removed all dissolved oxygen within 30 to 40 days. Developmentof anoxic conditions resulted in the release of large quantities of dissolved organic matter, plant nutrients, iron, manganese, and hydrogen sulfide. Upon comparison of these observations with other preimpoundment and postimpoundment investigations, several measures of potenial use were found to reduce the impact of initial soil flooding and decomposition of vegetation on the initial water quality of Richard B. Russell Lake. These included: burning of herbaceous vegetation in teh hypolimnion and removal of tops trimmed from trees from areas to be flooded by rpoject waters; application of the data in this report to reservoir operation through use of a mathematical water quality model; reduction of residence time for hypolimnetic waters in the reservoir through operation in the sluice gates; and use of the planned dissolved oxygen injection system during initial reservoir filling.