On the other hand, changes in lake thermal stratification also affects the nutrient cycle, such as the formation of the nutricline, especially in the upper layers of water bodies (Cermeño et al., 2008), and promotes the eutrophication of lakes and harmful algal blooms (Posch et al., 2012; Wilhelm and Adrian, 2008).
Full Answer
What is thermal stratification effects?
Our results indicated that the thermal stratification was mainly controlled by solar radiation and the thermal stratification favored the growth of cyanobacteria and led to the release of nutrients from the sediment, threatening the water quality.
How does stratification affect fish?
During middle and late summer, stratification commonly causes compression of even warm-water fishes into the stratum of water between the anoxic hypolimnion and the warm epilimnion where surface temperatures often exceed their thermal preferences.
How does stratification affect eutrophication?
During a mixing event after a long period of stratification, nutrients, sulfide, and other dissolved constituents are conveyed to the surface waters, potentially triggering eutrophication processes with direct consequences for ecosystem health status (e.g. algal blooms, odors and fish kills)4.
What factors cause the creation of thermal stratification?
The research found that air temperature, wind speed, and hydrodynamic factors are the driving factors for the thermal stratification and corresponding water temperature change patterns in Daheiting Reservoir.
Why is thermal stratification important?
The significance of thermal stratification to anglers is that the lower layer of water, deprived of surface contact, slowly loses its dissolved oxygen and become less able to support aquatic life.
What are the three types of thermal stratification?
There are three kinds of thermal stratifications. Epilimnion – The upper layer of warmer water. Metalimnion – The middle layer with a zone of a gradual decrease in temperature. Hypolimnion – The bottom layer of colder water.
How stratification affects water quality?
Stratification of the lake's waters prevents more oxygen from reaching the bottom water. Even so, the oxygen supply in the Eastern Basin does not get used up dur- ing the summer, because the supply was very high at the begin- ning of the summer.
How does stratification affect dissolved oxygen?
During summer stratification the thermocline prevents dissolved oxygen produced by plant photosynthesis in the warm waters of the well-lit epilimnion from reaching the cold dark hypolimnion waters. The hypolimnion only has the dissolved oxygen it acquired during the short two-week spring overturn.
What is meant by thermal stratification of lakes?
Definition. The thermal stratification of lakes refers to a change in the temperature at different depths in the lake, and is due to the density of water varying with temperature. Cold water is denser than warm water and the epilimnion generally consists of water that is not as dense as the water in the hypolimnion.
How thermal stratification affect the composition or quality of water in lake?
Thermal stratification occurs at a majority of deep reservoirs resulting from the surface warming. It stops mixing and prevents reaching oxygen to the bottom depths. These result water quality detritions in the bottom layers.
What is water stratification and why is it important?
Stratification is the separation of water in layers. Two main types of stratification of water are uniform and layered stratification. Layered stratification occurs in all ocean basins. Stratified layers act as a barrier to the mixing of water, which impacts the exchange of heat, carbon, oxygen and other nutrients.
What is heat transfer stratification?
Heat stratification — the natural rising of heat — costs businesses money, decreases worker productivity, wastes energy and stresses equipment. Stratification can even increase condensation spots, cause air stagnancy, and decrease the lifespan of lighting systems.
Why is water stratification important?
Stratification has important implications for fisheries management, phytoplankton (algae) populations, and water supply quality. A discussion of a few stratification impacts follows. Just after summer stratification is established, the hypolimnion is rich in dissolved oxygen from the early spring mixing of the lake.
What is stratification aquaculture?
Stratification is an unwanted consequence in aquaculture, because the upper, warmer, less dense layer of water (epilimnion) in which oxygen enters from the air and in which oxygen is produced by phytoplankton photosynthesis is separated from the deeper, cooler, denser water (hypolimnion).
What does stratification mean in water?
Stratification is a term used to describe when two distinct layers occupy the vertical water column in the sea: the near-surface one is less dense than the near-bed one (see also Stratification / potential energy anomaly assessment).
What causes stratification of water?
Stratification occurs as a result of a density differential between two water layers and can arise as a result of the differences in salinity, temperature, or a combination of both. Stratification is more likely when the mixing forces of wind and wave action are minimal and this occurs more often in the summer months.
What is thermal stratification?
Thermal stratification occurs when two types of steam with different temperatures come into contact. Their temperature difference causes the colder and heavier water to settle at the bottom of the pipe while allowing the warmer and lighter water to float over the colder water.
How does thermal stratification affect NPPs?
It typically occurs in pipe systems where the fluid flows at a low velocity with large temperature variance. Thermal stratification occurs when two types of steam with different temperatures come into contact. Their temperature difference causes the colder and heavier water to settle at the bottom of the pipe while allowing the warmer and lighter water to float over the colder water. When this thermal stratification phenomenon occurs, the pipe is submitted to loads due to the temperature difference between the upper and lower regions of its cross-section. The upper region of the pipe tends to expand; meanwhile, its lower region opposes this expansion. This phenomenon of simultaneous expansion and contraction causes longitudinal loads, which then bend the pipe as shown in Fig. 20.10 (the banana effect). At the same time, the lower part of the pipe (colder region) retains tension, while the upper part (hotter region) retains compression, at the separation interface of the fluids to sustain the geometrical orientation (or continuity). This in turn causes circumferential stresses that may deform the cross-section of the pipe, as can be seen in Fig. 20.11.
How does Lake Erie affect the ecosystem?
Of the five North American Great Lakes, Lake Erie was the most seriously impacted by cultural nutrient enrichment. Lake Erie is thought to be naturally more eutrophic than the other Great Lakes because of its shallower depth and the greater erodibility of nutrient-rich soils in its immediate drainage basin (i.e., excluding upstream Great Lakes). Lake Erie can be divided into three basins (Figure 2 ), distinguished by mean depth, that have distinct morphometric and trophic characteristics. The western basin (3,080 km 2) is the shallowest (mean depth 7.6 m), and most nutrient- and plankton-rich of the Lake Erie basins. The water column mixes completely throughout most of the year with brief and unpredictable periods of thermal stratification between May and September. The western basin is eutrophic, because it is shallower (see Section 9.08.2: Natural Eutrophication), and receives the largest external nutrient loads. The central basin, largest of the three in area (16,425 km 2) and volume has a mean depth of 18.6 m. Here, thermal stratification is established yearly between June and September, causing bottom waters to become hypoxic by late summer. The eastern basin (area 6,159 km 2) is by far the deepest of the three (mean depth 26 m). Thermal stratification is strongest in this basin and persists from June to late October or early November. The eastern basin is considered oligotrophic, and therefore the thick hypolimnion (bottom layer of cold water) experiences only small reductions in dissolved oxygen concentrations (Bartish, 1987). Thus, Lake Erie displays a longitudinal gradient in trophic status; from eutrophic waters in the western basin to progressively diluted and oligotrophic waters in the outflowing eastern basin.
What is thermal striping?
Another observation during thermal stratification is the local variation of temperature in the fluid interface known as thermal striping. Thermal striping causes high cycle thermal fatigue and cracks on the internal surface of the pipe. The thermal striping phenomenon is characterized by an oscillation frequency and amplitude ( Fig. 20.12 ).
How does mixing time affect microalgae?
Mixing time influences overall mass transfer, which in turn affects biomass function and process productivity [198]. Appropriate mixing is essential for the uniform supply of light to all microalgae within the reactor [91]. By mixing without internal fluid flow inside the reactors, some microalgae could absorb photons excessively while other others may not grow [91]. Sustaining a homogeneous cell suspension has been acknowledged as a fundamental parameter for higher biomass productivity of microalgae cultivation systems [199]. Mixing time can be used for all PBRs except the bubble column because it has only bubble injection into the stagnant culture medium with no inlet and outlet for the culture medium [91]. Adequate mixing keeps algal cells in suspension, removes thermal stratification, allows for uniform nutrient movement, and improves gas–liquid mass transfer to prevent oxygen accumulation, especially in tubular PBRs. It was also stated that when the nutritional requirements are adequate and the environmental conditions are optimized, mixing aimed at inducing turbulent flow would translate to high yield of algal biomass [200,201].
How does water quality change in lakes?
Water quality in lakes and reservoirs can change throughout the year as the water can stratify during warmer months . Thermal stratification can be a significant process in many lakes. During the warmer months of the year the warmer water (and therefore less dense water) will stay near the surface of the water body while the cooler and more dense water is trapped below. In the absence of strong winds there will be little mixing of the colder, denser water below with the warmer, less dense water near the surface. Under certain conditions where adequate nutrients are present this can lead to a depletion of oxygen in the lower parts of the water body and can thus cause water quality issues such as taste and odor problems and problems with iron and manganese (which will have increased solubility under the reducing conditions). As temperatures cool and the temperature of the surface of the lake cools, this together with wind action can cause mixing throughout the reservoir.
How does the speed of gas bubbles affect the diameter of the bubbles?
In closed photobioreactors, where the mixing is carried out by impellers or airlift, the increase of the speed of the gas bubbles enlarges the diameter of the bubbles ( Ugwu et al., 2008 ). The bigger the bubbles, the lower the exchanges of gases with the liquid.
What factors affect thermal stratification?
Through the analysis of the factors that affect the thermal stratification, the results indicated that both the meteorology and hydrodynamics can affect thermal stratification in Xiangxi River, while thermal stratification was more sensitive to the meteorological factors. It showed that air temperature was more closely related to thermal stratification, the second impact factors were the solar radiation, and then the inflow discharge, and the relationship between thermal stratification and other factors was not obvious in Xiangxi River.
How is thermal stratification determined?
Thermal stratification was determined both by meteorological variables (such as air temperature, wind speed, solar radiation and so on) and hydrodynamics, and the seasonal variation of meteorological and hydrological factors was obvious in Xiangxi River (see Table 1 ). Through analysis of the relationship of the different factors, including air temperature, wind, rainfall, inflow discharge and daily water level fluctuations, with the thermal stratification, the results showed that the RTRM had a strong positive relationship with the air temperature (r = 0.86, p < 0.05); the relationship of RTRM with other meteorological variables such as wind (r = −0.09, p < 0.05), rainfall (r = 0.12, p < 0.05) and solar radiation (r = 0.48, p < 0.05) was not significant. This indicated that the thermal stratification was more closely related to air temperature, then to solar radiation. The relationship of RTRM with inflow discharge (r = 0.37, p < 0.05) and daily water level fluctuation (r = 0.10, p < 0.05) was not obvious either (see Figure 3 ). The results indicated that the meteorology was a more important factor affecting thermal stratification than the hydrodynamics in Xiangxi River.
How does thermal stratification affect water quality?
The strong thermal stratification could influence the vertical distribution of the water's chemical characteristics, and the results showed that water quality was highly affected by thermal stratification and the Chlorophyll a concentration had a close relationship with thermal stratification and DO concentration.
How does wind affect water quality?
The effect of wind on the water body was also an important factor in some cases, because wind could induce the wind current to influence the thermal structure and water quality in the water body. Kimura et al. (2016) studied a small shallow lake in response to meteorological conditions and the simulated results showed wind sheltering altered current patterns, especially in sheltered areas. Magee et al. (2016) found that freeze-over water temperature, hypolimnetic heating, and fall turnover date were more closely related to wind speed. Snortheim et al. (2017) studied three meteorological drivers (air temperature, wind speed and relative humidity) of hypolimnetic anoxia in a eutrophic, northern temperate lake and found that wind speed had a negative correlation with the anoxic factor. Through analysis of the relationship of the wind speed with the water temperature difference between the surface layer and the bottom in Xiangxi River, the results showed that the relationship between wind speed and the water temperature difference between the surface layer and the bottom was not obvious (see Figure 4 ). It may be caused by the relatively small water surface, irregular shape and the far distance of the measured site from the estuary of Xiangxi River, which could result in low wind stress at the water surface, and then weaken the effect of wind on thermal stratification in Xiangxi River.
What is the critical value of RTRM?
The magnitude of RTRM is proportional to the strength of thermal stratification, a greater value means stronger thermal stratification, and the critical value is 50 for stratification according to the literature ( Chimney et al. 2006 ).
What is the climate of Xiangxi River?
Xiangxi River has a subtropical continental monsoon climate. The average annual air temperature is 17.1 °C, the highest air temperature usually occurs in August and the lowest air temperature usually occurs in February. The average annual wind speed is 0.73 m/s and it is usually stronger in spring and summer than in fall and winter. The average annual rainfall is almost 956 mm, with a range of between 900 mm and 1,200 mm, with most of the rainfall occuring during the summer months.
Why is turbidity vertical?
This may be caused by the algae in the upper water body and suspended solids in the lower water body.
What happens at the end of thermal stratification?
At the end of thermal stratification the surface waters of the epilimnion gradually cool as a result of conduction, evaporation and convection. Now the lake attains temperature uniformity from top to bottom. Because the water is now also of uniform density, it becomes well mixed by wind and wave action, a phenomenon known as ...
What happens to the water column after ice melts?
Following the ice melt, the surface water gradually warms to 4°C. At this point the water column is nearly isothermal, i.e., all the water is of uniform temperature and density. Hence, the strong spring winds cause considerable stirring, which results in a complete mixing of water, dissolved oxygen, and nutrients from the lake surface to the lake bottom, a phenomenon known as the spring overturn or spring turnover As the spring progresses, however, the surface waters naturally become warmer and lighter than the water at lower levels, as a result, the lake becomes thermally stratified into the following three zones (Fig. 4.10).
Which stratum has the highest dissolved oxygen concentration?
The upper stratum , which usually has the highest dissolved oxygen concentration and is characterized by a temperature gradient of less that 1°C per metre of depth, is the epilimnion (literally the “upon-lake” or the “upper lake”). This stratum contains more or less uniformly warm, circulating, and fairly turbulent water.
Why is water mixed with wind?
Because the water is now also of uniform density, it becomes well mixed by wind and wave action, a phenomenon known as the fall overturn or fall turnover As a result, the nutrients, dissolved oxygen, and plankton become uniformly distributed.
Which part of the water has a temperature gradient of less than 1°C per metre?
The lower stratum of water characterized by a temperature gradient of less than 1°C per metre of depth is the hypolimnion (literally the “lake below” or “Bottom Lake”). This part contains more dense, cooler, and relatively quiet water.
What is the temperature of the water at the bottom of a lake?
The water at increasing depth below the ice is progressively warmer and denser. The heaviest water, at the bottom of the lake, has a winter temperature of 4°C and throughout winter the water remains relatively stable.