JP4861203B2 - Method for evaluating the location of a fence for muddy water countermeasures and method for installing a fence for muddy water countermeasures using the evaluation method - Google Patents

Description

  The present invention relates to a method for evaluating the location of a fence for muddy water countermeasures for preventing and suppressing the occurrence of water quality failure due to stratification destruction such as turbidity during floods as represented by dam reservoirs, and muddy water using the evaluation method It is related with the installation method of the fence for a countermeasure.

  In closed water areas such as dam reservoirs, when large-scale flooding occurs due to rainfall, a large amount of turbidity such as soil particles flows from the catchment area and the stored water becomes turbid. The problem is that the so-called muddy water prolongation phenomenon occurs. This is because even clear river water that flows into the reservoir at the time of normal water becomes turbid due to the discharged sediment at the time of water discharge. Such river muddy water has been confirmed and reported by measuring numerical values such as BOD, T-N, T-P, and SS of rivers (for example, see Non-Patent Document 1). And in this nonpatent literature 1, it is reported that the river water quality at the time of flooding raises not only the turbidity by a stream sediment but also a nutrient concentration.

  As one of the countermeasures for prolonging muddy water at the time of flood in such a reservoir, as shown in FIG. 1, a reservoir in which a floating fence 3 is installed so as to pass to both banks in the reservoir 2 upstream of the dam 1. Equipment has been proposed (see, for example, Non-Patent Documents 1 and 2 or Patent Document 1). Here, the fence 3 includes a fence body 30, a float 31 for floating one side edge of the fence body 30 in the reservoir 2, and a weight 32 for sinking the other side edge of the fence body 30 toward the lake bottom. The other side edge to which the weight 32 is fixed forms the deepest part of the fence 3.

  According to such a water storage facility, by installing the floating fence 3 in the reservoir 2, the reservoir 2 is divided into an upstream side 2a and a downstream side 2b with the fence 3 as a boundary. The inflow water flowing into the reservoir 2 flows under the deepest portion 32 from the upstream side 2a and flows in the upper layer portion of the downstream side 2b blocked by the fence 3 to generate a portion where the flow of the inflow water hardly occurs. it can. Hereinafter, the upper layer portion in which the flow of inflow water downstream of the fence is difficult to generate is referred to as a fractionation layer 4, and the lower portion thereof is referred to as a lower inflow layer 5.

  If the floating fence 3 is installed in preparation for a flood in this way, when the inflow water in the flood flows from the upstream side 2a to the downstream side 2b and is discharged from the dam 1, the downstream side 2b mainly flows into the lower layer. Flow through layer 5. In the fractionation layer 4 which is the upper layer of the lower inflow layer 5, the stratification is protected by the action of the fence 3, and even if the inflow water is contaminated, it can be maintained without being contaminated. As a result, if the amount of the accumulated water staying in the fractionation layer 4 is increased, the majority of the stored water in the reservoir 2 is avoided from contamination, thereby shortening the turbidization period of the discharged water. it can.

  The presence / absence of the fence 3 and the influence on the turbidization period when the fence 3 is additionally installed are analyzed by simulation using an unsteady two-dimensional model (for example, see Non-Patent Document 1). There, the effects of flooding scale and fences or selective water intake measures are verified in relation to the number of internal fluids. If no fences are installed (when no countermeasures are taken), even if there is small scale and low possibility of stratification destruction, long-term turbid water Has been reported, and the effectiveness of the fence has been confirmed.

Moreover, the muddy water simulation at the time of the flood in the reservoir 2 is also examined (for example, refer nonpatent literature 3).
JP-A-2005-120582 Katsumi Uda, “On the clear stream conservation measures of the lotus dam (4D-P28)”, Proceedings of the 9th World Lake Conference (Shiga Prefecture), P529-532 (November 11, 2001) Yoshimura Sa et al., “Survey Report on Water Quality Management in Terauchi Dam Reservoir”, Dam Technology No. 114, P1-P12 (March 1996) Shin Umeda et al., “Development of a simulation model for muddy water during floods in a dam reservoir”, FY 2002 dam water source environmental technology laboratory report p3-p17, dam water source environment center (issued in November 2003)

  Although it has been confirmed that the installation of a fence is effective as a countermeasure against prolonged muddy water, when a fence is levitated and installed, what type of fence (for example, fence depth h) is placed where ( Or sufficient examination is not made about whether it should install in the distance from the lake bottom 2c to the deepest part 32 = opening height). The current situation is that the installer installs it based on experience and intuition, considering the installation environment as appropriate.

  If the fence specification (fence depth h) is inappropriate, the effective volume of the fraction layer cannot be secured sufficiently. In dam reservoirs, etc. that need to take measures to prolong muddy water, there are various conditions that affect muddy water such as flood scale and topography. Therefore, a basic method for evaluating and determining the optimal fence specifications and installation location is proposed. Is desired.

  Further, in Non-Patent Document 1, the presence or absence of the fence 3 and the effect on the muddy water period when the fence 3 is additionally installed are analyzed by simulation using a non-stationary two-dimensional model in relation to the current fence. However, it has not been specifically studied where to place the fence or how deep the fence should be when the fence is levitated.

  In addition, Non-Patent Document 3 only examines turbid water simulation during flooding in the reservoir 2, and when installing the fence in the same manner, where to place the fence or what depth of the fence It has not been examined whether it should be a level.

  In dam reservoirs, etc., there are various conditions that affect muddy water generation such as flood scale and topography. There is a problem that information is enormous and conditions are complicated.

  At present, the evaluation method of the fence installation position and fence depth by such simulation analysis is considered to be unclear including the arrangement of the model to be used.

  Therefore, an object of the present invention is to provide a method for evaluating the installation position of a fence for countermeasures against muddy water, which can quantitatively evaluate the installation position even if necessary input data is narrowed down.

  Therefore, the present inventors examined a method for evaluating the fence specification and installation position of a fence for countermeasures against muddy water even if the necessary input data is narrowed down. Based on this, the present inventors have recognized that an optimum fence specification and installation position setting method according to flood scale and stratification can be provided.

That is, the present invention forms a fractionation layer that is fractionated by a fence on the upper layer on the downstream side of the fence by placing the fence for preventing muddy water so as to pass over both banks of the reservoir. A method for evaluating the position of a fence for muddy water countermeasures that avoids prolonged pollution of the reservoir by passing through muddy water through the fence and flowing down the lower layer below the fractionation layer,
Whether the installation position or depth of the fence for muddy water countermeasures is appropriate by using a hydraulic index that focuses on the stability of the fractionation layer secured on the downstream surface layer when the floating fence is installed Is a method for evaluating the position of a fence for muddy water countermeasures.

  This hydraulic index is exemplified by the Froude number represented by the following formula (I) or the Richardson number represented by the following formula (II).

Where Fd: number of internal fluids
Ri: Richardson number
v: Inflow velocity (m / s)
g: Gravity acceleration (9.8m / s ² )
ρ ₁ : Lower layer water density (g / cm ³ )
ρ ₂ : Upper layer water (downstream surface water) density (g / cm ³ )
h: Fence depth (m) for muddy water countermeasures.

  Such an evaluation method of the installation position of a fence for muddy water countermeasures can be applied to a method for installing a fence for muddy water countermeasures. For example, the hydraulic index is a function of turbid water inflow, reservoir topography, and stratification conditions, and setting the turbid water inflow and stratification conditions sets the minimum required total water depth at which the fence should be installed. Conditions can be calculated, and the fence can be installed at a position that satisfies the calculated minimum total water depth condition.

  Here, the stratification condition is, for example, a stratification thickness and a water density difference between stratification water forming the stratification and lower layer water forming the lower layer of the stratification.

  According to the present invention, the installation position can be quantitatively evaluated even if necessary input data is narrowed down. As a result, a simple and rational evaluation can be performed at the planning stage of countermeasures for the installation of fences for muddy water countermeasures, etc., by conducting a macro analysis focusing on necessary data. In addition, detailed numerical simulation that generally requires a large amount of work can be greatly rationalized.

Below, the outline of the hydraulic experiment using a reservoir model is demonstrated about the best form for implementing this invention.
[Outline of hydraulic experiment]
(Reservoir model)
First, FIG. 2 is a diagram for explaining a reservoir model used for a hydraulic experiment for explaining the water storage facility provided with the floating fence shown in FIG. In the following description, the part member having the same function as the water storage facility shown in FIG. 1 is given the same number or the same name in the reservoir model to simplify the description, and detailed description may be omitted. .

  In FIG. 2, reference numeral 2 is a reservoir model (reservoir model 2) constituted by a rectangular container extending in the longitudinal direction. This reservoir model 2 describes the main part of the reservoir blocked by a dam. Yes. In this reservoir model 2, a floating fence 3 is installed so as to pass over both banks. In the embodiment, the fence 3 has a fence body 30, a float 31 for floating one side edge of the fence body 30 in the reservoir 2, and the other side edge of the fence body 30 settling toward the lake bottom 2 c. The other side edge to which the weight is fixed forms a deepest portion 32 of the fence 3.

  In addition, after confirming that the fence maintained an almost vertical posture against the running water within the experimental flow rate in the preliminary experiment, an impermeable rigid fence was used in the experimental model to simplify the model.

  In such a reservoir model 2, the fence 3 is divided into an upstream side 2 a and a downstream side 2 b, and the inflow water flowing into the reservoir 2 passes under the deepest part 32 from the upstream side 2 a and passes through the lower inflow layer 5. Flowing. In the upper layer portion of the downstream side 2b that is blocked by the fence 3, a fraction layer 4 that hardly causes the flow of inflow water is formed.

Here, symbol H is the total water depth of the reservoir model 2 (or reservoir 2), symbol h is the fence depth, symbol d is the opening height of the fence 3 (distance from the lake bottom 2c to the deepest part 32), and H = h + d is satisfied. In addition, ρ ₁ is the density of the lower inflow layer 5 and ρ ₂ is the density of the fractionation layer 4 (upper water density). Generally, the upper water density ρ ₂ is the lower layer water density ρ _{1 made of} muddy water inflow water at a low temperature. Lower density (ρ ₁ > ρ ₂ ).

As a prototype of the reservoir model 2 employed in this hydraulic experiment, the reservoir 2 having a width of 200 m, a water depth of 30 m, and a maximum set flow rate of 750 m ³ / sec was assumed. A fence width of 15 m was cut out from the fence disposed across the reservoir 2 to obtain a reservoir prototype amount, and a hydraulic model amount with a 1/50 two-dimensional channel similar to the Froude number was obtained. Three types of fences with depths of 5 m, 10 m, and 15 m were prepared, and details of these reservoir prototypes and hydraulic model quantities are shown in Table 1.

(Experiment)
In order to change the density of the lower layer water density ρ ₁ due to the difference in salt concentration added to the pure water and to visually observe the change of the flow state and the stratified state, the dye was added to only the lower layer water (inflow water) and colored. .

As shown in Table 2, the density difference (ρ ₁ −ρ ₂ ) Δρ between the upper layer water density ρ ₂ and the lower layer water density ρ ₁ and the flow rate of muddy water were changed according to the planned values. An electrical conductivity measuring device and an anemometer were disposed at appropriate locations on the reservoir model 2, and the inflow velocity and electrical conductivity at that time were measured. As a result, it was confirmed that changes in flow velocity distribution and conductivity distribution across the reservoir were negligibly small, and the densities ρ ₁ and ρ ₂ indicating the stratified state downstream of the fence were almost the same as the planned values. It was.

Next, under the conditions shown in Table 2, the lower layer water visualized the fluctuation state (stratified interface rise amount) of the interface position (climbing layer position) when the fence depth h, density difference Δρ, and flow rate were changed, respectively. The boundary between (inflow water) and colorless upper layer water was measured on a scale by visual observation at 25 m, 50 m, 75 m, 100 m, 150 m, 200 m, and 250 m points starting from the fence position.
(result)
From the analysis of the experimental results, as shown in FIG. 3, the position of the stratification interface showed an increase in the stratification interface between the fractionated layer and the lower layer water due to the fence when the lower layer was stationary, as shown in FIG.

  Although the amount of increase ΔU at the stratification interface slightly changes in the flow direction, the change amounts of a plurality of measurement points arranged in the flow direction are averaged, and the results are also shown in Table 2, and for each fence depth h FIG. 4 (density difference Δρ: 1000 ppm) and FIG. 5 (density difference Δρ: 2000 ppm) are summarized in FIG.

  From FIG. 4 and FIG. 5, when the same density difference Δρ and the same fence depth h are compared, it is confirmed that the interface rise amount ΔU increases as the flow rate increases. Further, from the comparison between FIG. 4 and FIG. 5, it was recognized that the interface rise amount ΔU tended to decrease as the density difference Δρ increased if the other conditions were the same.

  However, for the fence depth h, at the same density difference Δρ, when the fence depth h = 10 m and the fence depth h = 15 m are compared, the fence depth h = 15 m tends to increase the interface rise amount ΔU. It was confirmed that because the total water depth was constant, it was thought that the lower layer inflow velocity was larger, but the change was greater at the fence depth h = 5 m than at the fence depth h = 10 m.

  From the above results, it is confirmed that the determination of the fence depth h cannot be simply evaluated by the lower layer inflow velocity, and if the total water depth is constant, an optimum value exists for the fence depth h. It was suggested that if the depth h is constant, there is a requirement for the total water depth necessary to stabilize the stratified state.

Therefore, the present inventors tried to organize the obtained results by the relationship between the amount of increase in the stratification interface and the number of internal fluids or the number of Richardsons, and the results are shown in FIGS. Here, the internal fluid number _Fd and the Richardson number _Ri are the following formulas (I) and (II) defined in FIG.

As a result, as shown in FIGS. 6 and 7, the amount of increase ΔU at the stratification interface is proportional to the internal fluid number F _d , which is an index of the relationship between the inflow velocity and the stratification strength, and inversely proportional to the Richardson number R _i. It was confirmed that the

This makes it easy to set the density difference (Δρ = ρ ₁ −ρ ₂ ), turbid water inflow rate (or inflow velocity), etc., using the relationship between the internal fluid number or Richardson number and the stratified interface rise. Or, from the measurable value, it was considered that the fence stratification retention effect by the fence depth h and the installation position could be quantitatively evaluated.

Next, specific examples will be described, but the present invention is not limited to these examples.
Example 1
In reservoirs and the like, it has been confirmed that the thickness of the initial stratification state (cracking position) is substantially constant from many other data obtained by measuring the temperature distribution. Therefore, in the first embodiment, the fact that the initial climbing layer position is constant is used, and the fence position is set when this climbing layer position is set as the fence depth.

First, the vertical density distribution of the reservoir as the fence installation target is measured. Since the vertical density distribution of the water staying in the reservoir is substantially uniform in the horizontal direction, the initial stratified thickness (climbing position) h is set. Further, the density difference Δρ (ρ ₁ −ρ ₂ ) between the upper layer water density ρ ₂ and the lower layer water density ρ ₁ is obtained from the measurement result of the density distribution, and the density difference Δρ (kg / m ³ ) and the lower layer density ρ ₁ (kg The ratio Δρ / ρ ₁ to / m ³ ) is grasped.

Then, from these values, (Δρ / ρ ₁ ) * g = g '(m / s ² ) is calculated as a hydraulic index of stratification strength, and the set stratum position (fence depth) h (m) Is used to calculate g′h (m ² / s ² ). Here, g is the gravitational acceleration (m / s ² ).

Next, an allowable value a is set for the Froude number F _d of the formula (I) to obtain the formula (I ′).

  When this formula (I ') is arranged with respect to the inflow velocity v (m / s), formula (III) is obtained.

  From this equation (III), the limit condition (maximum flow velocity) of the inflow velocity which is the maximum value of the inflow velocity v (m / s) is obtained.

Next, if the unit width flow rate of a reservoir or the like is Q (m ² / s), the total water depth is H (m), and the opening height is d (m) (d = H−h), the inflow velocity v is v = Q / d = Generalized as Q / (H−h) (m / s). As a result, the allowable value a is set for the Froude number F _d of equation (I) to obtain equation (I ″).

  When this formula (I ″) is arranged at the total water depth H, formula (IV) is obtained.

  In this formula (IV), the fence depth h is the climax position set from the measured density distribution, and if the value of the unit width flow rate Q is set, the minimum value of the total water depth H, that is, necessary The total water depth H is calculated.

Accordingly, if the fence depth and the unit width flow rate are set to predetermined values, the necessary total water depth H is obtained. Therefore, the fence is installed from the position satisfying this total water depth H, with this total water depth H as the minimum total water depth condition. It will be sufficient to select. Usually, since the bottom 2c of the reservoir is inclined, the total water depth H differs from the installation position. If the fence 3 is installed at a specific position of the lake bottom 2c that satisfies this total water depth H (or opening height d), the total water depth H (minimum total water depth condition) can be satisfied. The installation position of the fence 3 satisfying the condition can be specified.
(Example 2)
Next, an example in which the initial stratified thickness (climbing layer position) does not match the fence depth h of the fence 3 to be used will be described.

  In an actual reservoir or the like, the stratified state does not necessarily coincide with the fence depth h, and the installed fence depth h may not work effectively in the formation of the fractional layer. In addition, the water temperature of the surface layer rises due to the influence of solar radiation during the daytime, and the degree may vary greatly depending on weather conditions.

  Therefore, in this embodiment, as an example in which the initial stratified thickness (climbing layer position) does not match the fence depth h, as shown in the temperature distribution 9 of FIG. An embodiment will be described in which the evaluation method according to the present invention is applied to a water storage facility in which a temperature increase is observed as the temperature distribution in the depth direction) approaches the surface layer.

  In such a water storage facility having a temperature distribution 9, an analysis assuming that the initial density distribution is replaced with a two-stratified field may be performed. However, the downstream side 2 b which is substantially the same depth as the deepest portion 32 of the fence 3 may be used. In the vicinity of the bottom surface 4a of the image layer 4, one or a plurality of aeration devices 8 are disposed as a stirring device (circular flow generating device in the surface layer).

  If such an aeration apparatus 8 is provided, the stagnant water in the fractionation layer 4 can be stirred in the vertical direction by the bubbles 8a discharged from the aeration apparatus 8. As a result, the temperature distribution in the vertical direction (depth direction) of the fractionation layer 4 is such that the temperature distribution 9 when no countermeasure is taken increases rapidly toward the surface layer, whereas the temperature distribution 9 ′ when the countermeasure is taken Exhibits a substantially uniform temperature distribution in the vertical direction in the fractionation layer 4.

  If the density distribution improvement technology using such a circulating flow generator in the surface layer is applied, when the stratification thickness is extremely thin relative to the fence depth, by increasing the stratification thickness, Layer position) and fence depth can be matched.

Further, if such a density distribution improving technique is applied, the density distribution of the fractionation layer 4 is different from the density distribution in the initial stratified state. Therefore, if the total water depth H is calculated again in accordance with Example 1, In addition, it is possible to quantitatively evaluate whether or not this density distribution improvement technique is appropriate for the target reservoir. Thereby, application of the above-mentioned Example 1 is attained, and a rough fence installation position can be obtained.
(Outline of muddy water countermeasure study system)
Based on the knowledge explained above, a muddy water countermeasure examination system according to the present invention as shown in FIG. 9 is proposed. The basic information necessary for the examination in FIG. 9 is the turbid water inflow, the topography (water depth) of the reservoir, etc., and the vertical density distribution indicating the stratified state in the initial conditions. The flow velocity is calculated from the turbid water inflow and the topography (water depth) of the reservoir, etc., and the vertical density distribution indicating the stratified state in the initial condition can be grasped by measuring the water temperature.

  Using these squeezed necessary information, the hydraulic index (Froude number or Richard) defined by the above formula (I) or (II) for the stability of the fractionation layer by the fence for countermeasures against muddy water Calculate the number of sons).

  These hydraulic indicators are considered to be constant except in special cases such as when technical measures to enhance stratification are taken. It is possible to conduct a unified and quantitative examination and evaluation of the allowable flow velocity and the optimum fence depth related to the turbidation control effect even under different circumstances.

  For example, by fixing the elements related to the stratification condition and the inflow rate in the relational expression (Formula I or Formula II) representing the hydraulic index, the installation position (opening height) is based on the relationship between the fence depth h and the total water depth H. It is possible to quantitatively compare and evaluate the countermeasure effect according to (d) by numerical values, and thereby, it is possible to formulate an introduction plan for the optimum installation location of the fence.

  In addition, in the above formula (I) or formula (II), an allowable inflow velocity (allowable flow rate) is obtained by setting an allowable value a of a hydraulic index assumed in advance or by additional examination. Thus, it is possible to evaluate whether or not the above-described countermeasure effect on the assumed inflow amount is effective.

  Furthermore, in cases where the initial stratification conditions do not match the fence depth h, it is considered effective to consider the application of a technology that improves the density distribution in the reservoir (for example, a circulating flow generator in the surface layer). Proposals can be made to increase the effectiveness of countermeasures.

  Furthermore, when conditions such as reservoir topography are complex and their effects are considered, sophisticated analysis techniques such as numerical simulation may be required to evaluate the effects. In such a case, by adopting an overall evaluation method such as the above-described introduction plan formulation, evaluation of countermeasure effects, and proposal for enhancement of countermeasure effects according to the present invention, it is possible to improve the accuracy of technology such as numerical simulation. Analysis cases can be narrowed down. As a result, the present invention can be additionally used for these high-precision techniques, and efficient analysis becomes possible.

  As described above, the present invention has been described with reference to the drawings. However, in order to evaluate the actual effect level, it is considered necessary to associate the value of each index with the actual measurement result. In addition, since this study is based on the assumption of simplified flow conditions, it is desirable to confirm the actual state of inflow density flow during floods.

  Furthermore, it is also possible to increase the prediction accuracy by numerical simulation reflecting the noted vertical mixing process, etc., as necessary for evaluating complicated terrain effects.

  According to this study flow, it is considered possible to quickly and easily determine the optimal installation position, installation water depth, etc. for maximizing the muddy water suppression effect by fences for muddy water countermeasures such as dam reservoirs.

It is a figure explaining the outline | summary of the water storage facility of the state which installed the fence for a general muddy water countermeasure. It is a figure explaining the Froude number or Richardson number as a hydraulic parameter | index. It is a figure explaining the rising situation of the stratification interface at the time of flood. It is a figure explaining the relationship between a flow volume and the amount of interface rises. It is a figure explaining the relationship between a flow volume and the amount of interface rises. It is a figure explaining the relationship between the fluid number as a hydraulic parameter | index, and the amount of stratification changes. It is a figure explaining the relationship between the Richardson number and stratification variation as a hydraulic index. It is a figure which shows typically the example of the stratification state change (change of temperature distribution) in the fractionation layer at the time of installing a circulation apparatus. It is a figure explaining the muddy water countermeasure examination system based on a proposal.

Explanation of symbols

1: Dam 2: Reservoir (reservoir model)
2a: Upstream side 2b: Downstream side 2c: Lake bottom 3: Fence 30: Fence body 31: Float
32: Weight (deepest part)
4: Fraction layer 4a: Bottom surface (stratified interface between fraction layer 4 and lower inflow layer 5)
5: Lower inflow layer 8: Stirring device (aeration device or surface layer circulating flow generation device)
9: Temperature distribution (temperature distribution when no measures are taken)
9 ': Temperature distribution (Temperature distribution during countermeasures)

Claims (4)

A fence for preventing turbid water is levitated and arranged so as to pass to both banks of the reservoir, so that a fraction layer separated by the fence is formed on the upper layer downstream of the fence, and the turbid water passes through the fence. A method for evaluating the location of a fence for muddy water countermeasures that avoids lengthening of reservoir pollution by flowing down the lower layer below the fractionation layer,
Whether the location of the fence or the depth of the fence for muddy water countermeasures is appropriate by using a hydraulic index that focuses on the stability of the fractionation layer secured on the downstream surface layer when the floating fence is installed The evaluation method of the installation position of the fence for the muddy water countermeasure which evaluates quantitatively. The hydraulic index is a Froude number represented by the following formula (I) or a Richardson number represented by the following formula (II): Evaluation methods.

Where Fd: number of internal fluids
Ri: Richardson number
v: Inflow velocity (m / s)
g: Gravity acceleration (9.8m / s ² )
ρ ₁ : Lower layer water density (g / cm ³ )
ρ ₂ : Upper layer water (downstream surface water) density (g / cm ³ )
h: Fence depth (m). A method for installing a fence for muddy water countermeasures using the method for evaluating the installation position of the fence for muddy water countermeasures according to claim 1 or 2,
The hydraulic index is a function related to the amount of muddy water inflow, the topography of the reservoir, and the stratification conditions. By setting the amount of muddy water inflow and the stratification conditions, the minimum total water depth necessary for the position where the fence should be installed is determined. A fence installation method for muddy water countermeasures, characterized in that the fence is installed at a position that satisfies the calculated minimum total water depth condition.   The stratified condition is a difference in water density between a stratified thickness and a stratified water that forms the stratified layer and a lower layer water that forms a lower layer of the stratified layer. Method.

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