The physical response of temperate lakes to artificial destratification

Abstract

Prolonged periods of thermal stratification in a lake suppress convective motions capable of vertical Prolonged periods of thermal stratification in a lake suppress convective motions capable of vertical transport of dissolved oxygen and other dissolved and suspended matter. When this leads to anoxia in the transport of dissolved oxygen and other dissolved and suspended matter. When this leads to anoxia in the hypolimnion, it can give rise to profound water quality implications. Artificial destratification is one means hypolimnion, it can give rise to profound water quality implications. Artificial destratification is one means whereby low oxygen levels in the hypolimnion may be averted. The operating principles of bubble plume whereby low oxygen levels in the hypolimnion may be averted. The operating principles of bubble plume destratification and its effect on the physical transport and mixing that occurs in a lake are described. destratification and its effect on the physical transport and mixing that occurs in a lake are described. Monitoring of temperature and dissolved oxygen was conducted at Lake Nepean, Australia, prior to the Monitoring of temperature and dissolved oxygen was conducted at Lake Nepean, Australia, prior to the destratification, and then continued for two summers while the destratification system was operating. The destratification, and then continued for two summers while the destratification system was operating. The results showed that artificial destratification had an immediate effect on lake motions across a range of scales. results showed that artificial destratification had an immediate effect on lake motions across a range of scales. The actual process of destratification occurred by the erosion of the base of the thermocline. Deep-water The actual process of destratification occurred by the erosion of the base of the thermocline. Deep-water temperatures were elevated well above historical values, the heat storage in the lake increased, and the time temperatures were elevated well above historical values, the heat storage in the lake increased, and the time of turnover was brought forward 2.5 months. An integral plume model coupled with a one-dimensional lake of turnover was brought forward 2.5 months. An integral plume model coupled with a one-dimensional lake model is shown to predict the effect of the bubble plume entrainment and the subsequent redistribution of model is shown to predict the effect of the bubble plume entrainment and the subsequent redistribution of the entrained water throughout the lake.The natural stratification that exists in most temperate lakes for a large part of the year effectively cuts off the hypolimnetic water from contact with the atmosphere and, hence, from a major source of oxygen. When this is coupled with generally increasing levels of nutrient input and the resulting increase in primary productivity (OECD 1982) there is a growing tendency for hypolimnetic water to become anoxic for significant periods of time. Aside from the...

Biological Effects of Incomplete Destratification of Hypertrophic Freshwater Reservoir

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