Water levels can be drawn down in impoundments to expose resident mussel infestations to air. Subsequent freezing during the winter or desiccation at high summer temperatures can be effective in killing a large proportion of the exposed population. The majority of the zebra mussel population could be exposed by lowering water levels since the mussels are usually restricted to shallow areas above the thermocline.
Zebra mussels can be effectively controlled by winter drawdown and exposure to subfreezing air temperatures (Payne 1992a). Clustered mussels are more tolerant of reduced air temperatures than are individual organisms. Exposure time for 100-percent mortality of individual mussels range from 15 hr at -1.5º C to less than 2 hr at -10 ºC. For clustered mussels, these times range from over 48 hours at -1.5 ºC to 2 hr at -10 C (Payne 1992a). (Figure 7) illustrates exposure times required for 100-percent mussel mortality in air temperatures ranging from -10º to 0º C.
Zebra mussels can also be effectively controlled in the summer by desiccation, although exposure times are longer than in winter months. Temperature is positively related and humidity negatively related to zebra mussel mortality. To ensure 100 percent mortality, aerial exposure must last nearly a month at moderately low temperature (5ºC) and high humidity (95-percent) but only 2 days at moderately high temperature (25ºC) and extremely low humidity (5 percent). However, even at high humidity (95-percent), 100 percent mortality is expected in approximately 5 days at 25ºC (Payne 1992b).