Drawdown is a measure of a lowering of the water level in a reservoir, well, or other body of water as the result of direct pumping or the general lowering of a water table, most often when more water is pumped from an aquifer than enters it through recharge, such as rainfall. Power demand, flood control measures, and irrigation all cause temporary, long-term, or sometimes effectively permanent drawdowns. Sometimes drawdowns are a remedy for specific environmental problems. For example, lowering the water level of a lake or reservoir can reduce or eliminate exotic plant populations and reduce aquatic weed cover, leading to the recovery of native plant and fish populations. Regular drawdowns, however, can deprive waterfowl of habitat and can make it difficult for native aquatic vegetation—the superior food for native fish and wildlife—to establish itself, thus putting all these forms of flora and fauna at risk. The expanse of muddy terrain exposed by draining a reservoir is sometimes referred to as “the drawdown.”

Jeffery Renard Allen