Hydrological extremes, water abstraction and reservoir operations are driving many lakes and reservoirs through low water, fragmented, dry and reflooded states. These transitions alter more than surface area and storage: they change residence time and connectivity, expose sediments to oxidation and desiccation, and reorganize exchanges among catchments, sediments, water and the atmosphere. Their sequence and duration can therefore generate thresholds, delayed recovery and persistent legacies in water quality and ecosystem function.
During contraction, solutes and contaminants may concentrate while littoral and bottom sediments become exposed. Drying changes redox conditions, microbial activity and organic matter processing. Reflooding can remobilize nutrients, salts, metals, suspended sediment and organic contaminants, trigger oxygen demand and greenhouse gas pulses, and reshape habitats and food web interactions. In managed reservoirs, the timing and rate of drawdown and refilling may amplify or reduce these effects.
The session will bring together hydrology, limnology, aquatic biogeochemistry, water quality, ecology, Earth observation and reservoir management. We invite field and experimental studies, in situ observations, water and sediment analyses, remote sensing, process based and data driven modelling, and regional or global assessments. Relevant topics include detection and attribution of state transitions; thresholds, hysteresis and recovery; sediment exposure and rewetting; carbon, nutrient and contaminant dynamics; ecological resistance and resilience; and monitoring, restoration and adaptive reservoir operation. By treating contraction, drying and reflooding as a connected trajectory, the session will examine when responses are reversible, when legacies persist, and how observations and management can reduce risks to water quality and ecosystem function.