What describes turnover in a reservoir?

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Turnover describes the vertical mixing of the entire water column in a reservoir, driven by density differences that come from temperature (and, if present, salinity). When stratified, layers stay separated, but turnover occurs when conditions allow the density of surface water to match the deeper water, enabling the whole column to mix. This often happens during seasonal transitions in temperate climates and redistributes heat, oxygen, and nutrients, which affects water quality for treatment. It’s not about evaporation, sedimentation rate, or how long water stays in the reservoir.