Abstract
BackgroundThermal stratification in reservoirs is a significant factor affecting water quality, and can be strongly influenced by climate change and operational strategies. Reservoirs in the temperate zone react most sensitively to climate warming during winter as ice cover and inversed stratification are about to disappear in a warmer world. In this study, two well-established hydrodynamic models, the one-dimensional General Lake Model (GLM) and the two-dimensional CE-QUAL-W2 (W2), were used to investigate the response of winter inversed stratification in the Rappbode Reservoir to future climate warming, combined with different water withdrawal elevations.ResultsUnder increased air temperature, the duration of inversed stratification is reduced and the inversion phenomenon will entirely disappear under current management if the air temperature is increased high enough (more than 4.5 K) in the future. Under strong climate warming, the Rappbode Reservoir will therefore change from a dimictic to a monomictic mixing type. Changing the reservoir management from deep withdrawal (e.g., below 350 m a.s.l.) to shallow withdrawal elevations (e.g., above 390 m a.s.l.) reduces internal heat energy stored in the reservoir in summer and prolongs the inversed stratification period in winter. This strategy can retain the dimictic behavior even under strong warming.ConclusionsOur study indicates that adjusting the withdrawal elevation is an effective management instrument to control the winter conditions and can, in fact, mitigate climate warming effects on winter hydrodynamics by stabilizing the dimictic mixing type.
Highlights
Introduction and backgroundThermal stratification is the phenomenon referring to a variation in the water temperature at different depths in a water body, and is the result of changes in water density with temperature [4]
The results show that the withdrawal location determines the thermocline depth and the hypolimnion volume; Çalıskan and Elçi [9] investigated the influence of selective withdrawal on the hydrodynamics of Tahtali Reservoir and concluded that hypolimnetic withdrawal is the most effective choice to encourage water mixing and reduce anoxia; Weber et al [45] developed an optimization withdrawal strategy which can automatically determine the withdrawal elevation to modify the thermal structures for different water usages
We focused on the combined influence of air temperature increase and withdrawal elevation on the duration of inversed stratification
Summary
Introduction and backgroundThermal stratification is the phenomenon referring to a variation in the water temperature at different depths in a water body, and is the result of changes in water density with temperature [4]. Little attention has been given to the winter inversed stratification in dimictic waters and its influencing factors. Thermal stratification in reservoirs is a significant factor affecting water quality, and can be strongly influenced by climate change and operational strategies. Reservoirs in the temperate zone react most sensitively to climate warming during winter as ice cover and inversed stratification are about to disappear in a warmer world. Two well-established hydrodynamic models, the one-dimensional General Lake Model (GLM) and the twodimensional CE-QUAL-W2 (W2), were used to investigate the response of winter inversed stratification in the Rapp‐ bode Reservoir to future climate warming, combined with different water withdrawal elevations
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