The Impact of Winter Drawdown on Macrophytes in a Colorado Reservoir

Nuisance growth of aquatic plants was noted within one year after Shadow Mountain Reservoir was constructed in 1946, and complaints about high macrophyte densities have continued intermittently since that time. An evaluation of potential management measures identified winter drawdown as the most practical control technique, although several factors complicate implementation of a drawdown in Shadow Mountain Reservoir. Results are presented for a drawdown conducted in 2006. Both average plant height and plant coverage were significantly reduced in the year following the drawdown. Additional monitoring is planned to evaluate the longevity of macrophyte control.