Lake Drawdown Construction Methods

Lake drawdowns are used as a method to control aquatic plant and animal life, in which the level of water is reduced by human means to expose an area of the lake or reservoir bed. The process of completing a lake drawdown is based on completing the drawdowns at regular intervals to ensure wildlife and residents of a lake or reservoir can prepare and become accustomed to the drawdown.

  1. Drawdown

    • Drawdowns are completed for reasons including power generation for hydro electrical plants, flood control and irrigation, and the control of aquatic plant species. The methods of completing a lake drawdown include the construction of a flood control structure, such as dams used with hydro electrical power generators, and through the use of high capacity pumps brought to a lake to lower the level of the lake or reservoir. A drawdown of a lake lowers the level of water by a predetermined amount, usually a few inches during periods of cold weather such as fall and winter, according to the State of Washington Department of Ecology. A drawdown is complete when the level of the lake is naturally replenished following the completion of the process.

    Plants

    • Lake drawdowns are commonly used to control aquatic plant life in a lake or reservoir; this control method is not scientific in nature, and can lead to other problems following the drawdown. A drawdown exposes an area of the lake bed to cold and freezing temperatures that limit the growth of targeted forms of aquatic plant life. The plants along the lakebed have their roots and seeds frozen for the period of the drawdown; as the lake is refilled, the frozen area of the lakebed surface is ripped off by the oncoming water, removing the plants attached to the bed.

    Nature

    • Certain limitations are created in using a drawdown, including damage to aquatic plants that are not in need of control, by draining a large area of the lakebed. Some targeted plants may also survive the freezing temperatures of the lake drawdown; the targeted plants may only be reduced in number for a short period of time before they return. During a lake drawdown, animal life that relies on the water of the lake or reservoir for survival may be damaged by the loss of their natural habitat. Animals such as turtles, frogs and beavers are among those that can be affected, the State of Washington Department of Ecology reports.

    Problems

    • The use the lake drawdown process can result in problems for the lake or reservoir ecosystem both during and after the drawdown takes place. These problems include the possibility of algae and other bacterial blooms within the lake following the drawdown, Newfound Lake reports. The residents of a lake can find problems including the lowered levels of wells providing residential water supplies.