JP2004037315A - Flow rate calculation method and flow rate calculation device of leak of ground water including sea water, and control device of amount of pumped water leak - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine simply the flow rate of a water leak including sea water without being influenced by alkaline earth metal ions such as a calcium ion which is a component derived from the sea water. <P>SOLUTION: The flow rate of the water leak including sea water has a linear relation with its electric conductivity. The relational expression is determined beforehand, and the electric conductivity of the water leak measured by using an electrode for electric conductivity measurement which is hardly influenced by the component derived from the sea water such as calcium ions for a long period is substituted into the determined relational expression, to thereby calculate the flow rate of the water leak. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for calculating a flow rate of leaked water, a flow rate calculating device, and a control device for controlling the amount of leaked water when there is a leak containing seawater in the groundwater, such as an underground structure such as an undersea tunnel, which is located near the seabed or the coast. Belongs to the field.
[0002]
[Prior art]
Today, underground structures such as tunnels and box culverts are frequently constructed below the water table or sea level, and such underground structures may not be able to drain the leaked water naturally. At this time, it is necessary to discharge the leaked water to the ground using power to avoid submergence of underground structures. The presence of groundwater is one of the causes of water leakage in such underground structures, but the amount of groundwater supplied depends on the natural environment (particularly rainfall) such as intensive heavy rainfall due to the rainy season and typhoons and drought. Sometimes, though slow, it changes. However, regarding the ability to discharge such water that has leaked into the structure, it is preferable not only in terms of efficiency to correspond to the flow rate of the leaked water, but also to grasp the state of the water leakage in terms of maintenance management and the security of the structure. Required for the above reasons. For that purpose, it is necessary to periodically measure the leakage flow rate, and the same can be said for an underground structure constructed near the seabed or the coast where seawater is mixed into the leakage water.
For measuring such a water leakage flow rate, for example, a triangular weir (or square weir) method is conventionally employed. This method is a generally widely used flow rate measuring method, in which a triangular weir capable of damming flowing water is formed at an appropriate position, and the depth of flowing water that is dammed up by the triangular weir and overcomes this. This is a direct measurement method of calculating the water leakage flow rate per unit time (for example, per hour or per day) from. However, in the triangular weir method, it is necessary to quickly form a firm seal using a sealing material such as clay so as not to leak water from the damming part, but after the measurement, it is provided for drainage. It is necessary to completely remove the used sealing material so that the sealing material does not flow into the storage tank, and there is a problem that the measuring operation is troublesome, complicated, and requires a long time. In addition, the triangulation method is a method in which the individual measurer actually measures a delicate amount of stored water, so that a plurality of measurers are required to ensure fairness in the measured value, and there is also a problem that the work efficiency is low.
[0003]
Then, the inventor of the present invention, as shown in Japanese Patent Application Laid-Open No. 2001-141545, shows that while the amount of groundwater leaking from the land side changes depending on the natural environment and the like, the amount of seawater leaking from the sea floor hardly changes. And the seawater component is predicted to be substantially constant. Based on this prediction, the concentration of a specific ion (for example, sodium ion), which is a component derived from seawater, in a leak containing seawater in groundwater (hereinafter referred to as “seawater-containing leak”) I guessed that there would be a first-order relationship with the leakage flow rate. And to prove this, actually, when measuring the concentration of specific ions and the leakage flow rate at that time for seawater-containing leakage leaking from underground structures, the concentration of specific ions and the leakage flow rate were We found that we could approximate the primary relational expression as inferred, and if we found the primary relational expression in advance, after that, we measured the concentration of specific ions in the seawater-containing water leakage, and converted the measured value to the primary relational expression. By developing a method that can easily calculate the flow rate of seawater-containing leaked water by substituting it into the equation, it has become possible to calculate the flow rate efficiently without the need for complicated measurements such as the triangular weir method. .
[0004]
[Problems to be solved by the invention]
However, the method for calculating the leaked water flow rate that has been developed requires the measurement of the concentration of specific ions in the leaked water to perform the calculation.As such a concentration measuring method, a method using ion chromatography, There is a method using an ion-selective electrode. However, in the former case, measurement at the site cannot be performed, and the leakage measured at the site is carried to the laboratory to measure the concentration, which is not only troublesome and complicated, but also the device itself is large and the cost is high. Problem. On the other hand, the latter can easily measure the concentration by immersing the ion-selective electrode in the on-site water leakage, but when the concentration is measured using the ion-selective electrode, the ion-selective electrode is thoroughly washed. In principle, measurement should be carried out using a sample that has been leaked.However, when there are multiple locations where water is leaked, it is not only troublesome to wash each one, but also the accuracy of the measured values due to poor cleaning. There is a problem that is damaged. On the other hand, it has been proposed that the ion-selective electrode be placed at the measurement site and kept immersed in the leaked water so that the measured values can be input at any time without using humans. If the measurement is continued, alkaline earth metal ions such as calcium ions will accumulate on the ion-selective electrode in a cumulative manner, destabilizing the measured values, and in some cases suddenly causing abnormal measured values. In some cases, the ion-selective electrode is not reliable because it may be observed. To avoid this, it is necessary to periodically clean the ion-selective electrode and remove the adhering ions. There are also problems to be solved by the present invention.
Furthermore, in an underground structure having a seawater-containing leak, it is necessary to pump out the leak by a pump. However, it is difficult to continuously grasp the leak flow rate, and there is a problem that the driving efficiency of the pump is low. There is a problem to be solved by the present invention.
[0005]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made for the purpose of solving these problems. The invention of claim 1 relates to a method of controlling the flow rate of leakage of groundwater containing seawater. Function of the relationship between the flow rate and the electric conductivity of the groundwater, the flow rate of the leaking water containing seawater in the groundwater, characterized in that the measured electric conductivity of the leaked water is substituted into the function and calculated. This is a calculation method.
Further, in the invention of claim 2, when calculating the flow rate of the leakage water containing seawater in the groundwater, the means for functioning the relationship between the flow rate of the leakage water and the electric conductivity, and the measured value of the electric conductivity of the leakage water Means for calculating the flow rate of leaked water by substituting it into a functionized one, to calculate the flow rate of leaked water.
By doing so, it is possible to calculate the leakage flow rate of seawater in the groundwater based on the measured value of the electric conductivity obtained using the electric conductivity electrode which is hardly affected by the adhesion of ions. Thus, a stable calculation of the leakage flow rate can be performed over a long period of time.
The invention of claim 3 is characterized in that, in claim 1 or 2, the relationship between the flow rate of water leakage and the electrical conductivity is a linear function. Can be calculated.
According to a fourth aspect of the present invention, in the third aspect of the invention, the linear function is obtained from a measured value of the flow rate of the water leakage and the electric conductivity. Wherein, in claim 3, the linear function is obtained by correcting the measured value of the flow rate of the leaked water and the concentration of the seawater-derived component by a relational expression between the concentration of the seawater-derived component and the electric conductivity. By doing so, the linear function of claim 3 can be obtained directly or indirectly.
According to a sixth aspect of the present invention, there is provided a control device for pumping water leakage, comprising: pump means for pumping water containing seawater from underground water from an underground structure; and control means for controlling the amount of water pumped by the pump means. In the meantime, the control means includes an input means for inputting a measured value of the electric conductivity of the water leakage, and the electric conductivity inputted into a function formula obtained because the flow rate of the water leakage and the electric conductivity are measured in advance. And a determining means for determining a pumping amount of the pump means based on a leakage flow rate obtained by applying the measured value of the above. With this configuration, pumping of water leakage from the underground structure by the pump means can be performed according to the leakage flow rate, and the driving efficiency of the pump means is improved.
According to a seventh aspect of the present invention, in the sixth aspect, the control device is connected to an electrode for measuring electric conductivity which is set up at an arbitrary place where a predetermined water leakage occurs, and the electric conductivity measured by the electrode is measured. In this case, the measurement of the electric conductivity can be efficiently performed without human intervention.
In the invention according to claim 8, in claim 7, a plurality of measurement positions are set, and a total leakage flow rate is calculated by adding a leakage flow rate calculated from each measured value of the electric conductivity at the plurality of measurement positions, It is characterized in that the pumping amount of the pump means is determined based on the total flow rate of the leaked water. By doing so, it is possible to perform the leaking pumping control with higher accuracy.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
As described above, seawater-containing leakage that leaks from underground structures is governed by a simple dilution rule of groundwater that changes due to the natural environment and almost a certain amount of seawater that leaks from the sea floor, It has been found that the concentration of a specific seawater-derived component in a seawater-containing leak and the flow rate of the leak can be approximated by a linear relational expression.However, if the seawater-derived component is not bio-metabolized and undergoes no chemical change, the seawater-containing leak Inferring that the concentration of seawater-derived components in the water could be directly replaced by the electrical conductivity of the leak, and in order to prove this, the concentration of the seawater-derived components in the seawater-containing leak and the electrical conductivity of the leak Examination of the relationship with the rate revealed that they had a linear function relationship, and completed the present invention.
That is, it has already been confirmed as described in the above-mentioned publication that the flow rate of the seawater-containing leak in the underground structure and the concentration of the component derived from the seawater are in a primary relationship, By taking into account that the concentration of the derived component and the electrical conductivity have a primary relationship, the flow rate of the seawater-containing leakage, the concentration of the seawater-derived component, and the electrical conductivity are in a linear relationship with each other. From this, if the relationship between the flow rate of seawater-containing leakage water and the electric conductivity is obtained in advance and a function is obtained, the electric conductivity of the seawater-containing leakage water can be determined using an electric conductivity electrode that is not affected by the adhesion of ions. The present invention has been completed by confirming that a reliable and stable flow rate of seawater-containing leakage can be calculated by measuring the rate and substituting the measured value into the function obtained above.
In this case, the relationship between the flow rate of the seawater-containing leak and the electrical conductivity, which is determined in advance, is a linear relationship between the flow rate of the seawater-containing leak and the concentration of the specific seawater-derived component, and the concentration of the specific seawater-derived component. It is not limited to that obtained indirectly by correcting based on the primary relationship between the electric conductivity and the electric conductivity, but the flow rate and electric conductivity of the seawater-containing leakage are measured to determine the relationship between the two. Of course, it may be determined directly.
[0007]
By the way, in carrying out the present invention, not only the flow rate of the underground water in the seawater-containing leakage water but also the flow rate of the seawater is affected by the ground and the leakage path between the seabed or the seashore and the measurement position, and so on. It is specific to the measurement position, and as a result, the relationship between the water leakage flow rate and the electrical conductivity at any position is specific to the arbitrary position and should be used as a function of all other positions. However, it is necessary to previously formulate the relationship between the flow rate of water leakage and the electrical conductivity at each measurement position. For this functionalization, it is preferable to perform statistical processing on the corresponding measurement values in order to improve accuracy.In this case, it is preferable to use a generally known calculation method such as a least square method. it can.
By the way, since groundwater also contains various groundwater-derived components such as sodium ions, for example, the relationship between the sodium ion concentration and the electrical conductivity of seawater-containing leakage water varies depending on the measurement position. If the amount of the component is small and negligible relative to the component derived from seawater, the relationship between the sodium ion concentration obtained by diluting seawater with pure water and the electrical conductivity is calculated as the sodium ion concentration of the seawater-containing leak. And the electrical conductivity can be adopted as a relational expression.
[0008]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of an existing submarine tunnel. The submarine tunnel has a main shaft 1 and a working shaft 2, of which the main shaft 1 has a gradient change point that becomes deeper toward the middle of the tunnel. And is built in a substantially V-shaped inclined state. On the other hand, the work pit 2 is constructed in a substantially inverted V-shape which is inclined so that it becomes deeper toward the wellhead with the deepest position of the main well 1 being a gradient change point, and the vertical shaft 3 is located at a ground position on each wellhead side. 4 have been built.
[0009]
And for (a) ~ (e) the position and the work of anti-2 (f) ~ (i) position of the Honko 1, leakage flow rate: the ^{(m 3} day ^-1 minus 1 square of the cube day meters) In addition to being measured by the triangular weir method, the electric conductivity (mS cm ^-1 : millisiemens centimeter minus 1 power) and sodium ion concentration (μg mL ^-1 : microgram milliliters minus 1 power) in the leaked water are measured. Was measured. FIG. 2 is a plot of the measured values of the electric conductivity and the sodium ion concentration, and FIGS. 3 to 9 are plots of the measured values of the electric conductivity and the water leakage flow rate at each of the positions (a) to (g). This is shown. When observing these plotted graphs, it was confirmed in FIG. 2 that the relationship between the electric conductivity in the leaked water and the sodium ion concentration was in excellent agreement with the linear function. And delineated this. Then, when the square value of the correlation coefficient (r) between the linear function and the plot value was calculated, “r ² = 0.9938” was obtained, which was very close to “1”. It was confirmed that the ion concentration had a high linear function relationship. Incidentally, the primary relationship between the electrical conductivity and the concentration of seawater-derived components is not only between sodium ions, but also for potassium, magnesium, calcium, chloride, and sulfate ions. I have confirmed.
[0010]
As described above, it was confirmed that the flow rate of the leaked water, the concentration of sodium ion derived from seawater, and the electrical conductivity had a linear relationship with each other, and there were a plurality of measurement data of the flow rate of the leaked water and the sodium ion concentration in advance. In this case, the measured flow rate data (or the relational expression between the flow rate of the leaked water and the sodium ion concentration) is corrected by the linear relational expression between the electric conductivity and the sodium ion concentration to obtain the flow rate of the leaked water and the electric conductivity. Relationship is indirectly required. Further, if there are a plurality of measured value data of the flow rate of the water leakage and the electric conductivity, the relation between the flow rate of the water leakage and the electric conductivity corresponding thereto can be directly obtained. 3 to 9 show the relational expressions (measurement positions (h) and (i) are shown in the drawings) based on the measured values of the flow rate and electric conductivity of the water leakage at the measurement positions (a) to (g). These relational expressions were obtained by correcting measured value data of the flow rate of water leakage and sodium ion concentration with the above-mentioned relational expression of electric conductivity and sodium ion concentration. It has been confirmed that the relational expression almost coincides with the relational expression. From this, it is confirmed that any one obtained by any method may be used as the relational expression of the present invention.
[0011]
Next, FIG. 10 shows a leakage flow rate calculation device which also serves as a control device for pumping out water from one of the shafts 3 (the control of pumping out water from the other shaft 4 can be performed in the same manner. However, the calculating device 5 includes an input unit 6 such as a keyboard, and a control unit (such as a personal computer) 8 having a display unit 7. The control unit 8 includes a calculating (calculating) unit 9. , Registration (storage) means 10 and determination means 11 for determining the amount of water to be pumped out, and the control unit 8 is immersed in the water leaks at the corresponding water leak positions (c) to (g). Each electrode (sensor: usually formed of a platinum electrode) 12 for measuring the electric conductivity, which is disposed so as to be stationary, and a pump unit for pumping up the water stored in the water storage tank 3a of the one vertical shaft 3. 1 The storage leak detection sensors 14 provided in the leak storage tank 3a are respectively connected to calculate the leak flow based on the measurement values input from the respective electrodes 12, and calculate the sum of the calculated leak flow. The pumping amount of the pump unit 13 is controlled based on the total flow rate X and the measured storage amount Y measured by the stored leakage amount sensor 14.
[0012]
First, in the control unit 8, the measured values of the flow rate and the electric conductivity of each leak position set as appropriate are input via the input means 6, and based on the input measured values, A primary relational expression between the flow rate of water leakage and the electric conductivity is calculated by the calculating means 5, and the primary relational expression is registered in the registration means 10. Then, the control unit 8 substitutes the measured value input from the electrode 12 disposed at each leak position into the registered primary relational expression, calculates the leak flow rate at each corresponding position based on this, and displays them on the display. The information is displayed on the display unit 7 and the pumping amount of the pump unit 13 is controlled.
[0013]
Here, in the pumping amount control, the total leakage flow X of the leakage flowing into the leakage storage tank 3a is calculated from the calculated leakage flow, and the pumping control of the pump unit 13 is performed based on the calculated total leakage X. An example of the control will be described with reference to the flowchart of FIG. Here, the pump unit 13 will be described on the assumption that first and second constant-capacity pumps 15 and 16 are provided side by side, and can separately pump out stored leakage water. The above-mentioned control unit 8 performs a system start by activating the corresponding software and performs initial settings such as data reading. In this case, first, the electric conductivity of water leakage at each of the above-described measurement positions is first measured. The total leakage flow rate X is calculated from the leakage flow rate calculated based on the measured values. Then, it is determined whether or not the total leakage flow rate X is equal to or less than a first preset total flow rate A (X ≦ A?). When it is determined that the total leaked water flow X is equal to or less than the first set total flow amount A, the measured storage amount Y measured by the stored leak amount sensor 14 is further reduced to a predetermined first set storage amount R or less. It is determined whether or not there is (Y ≦ R?), And if it is determined that the storage amount is equal to or less than the first set storage amount R, the first and second pumps determine that the storage leakage is small and the leakage flow rate is small. 15 and 16 are both controlled to stop and return. On the other hand, when it is determined that the measured storage amount Y is larger than the first set storage amount R (Y> R), the measured storage amount Y is further set as a value larger than the first set storage amount R. It is determined whether or not (Y ≦ S?) Is equal to or less than the second set storage amount S (R <S). Is in the normal range, and the storage leakage is also the normal amount, and only the first pump 15 is driven to perform the pumping control in the normal state. On the other hand, if it is determined that the measured storage amount Y is larger than the second set storage amount S (Y> S), the leakage flow rate is in the normal range, but the first and second storage amounts are determined to be large. The two pumps 15 and 16 are controlled to drive the pumps at an early stage, respectively, and return.
[0014]
On the other hand, when it is determined that the total leaked water flow rate X is larger than the first set total flow rate A (A <X), the total leaked water flow rate X is set in advance as a value larger than the first set total flow rate A. It is determined whether or not (X ≦ B?) Is equal to or less than the second set total flow rate B (A <B). If it is determined that the measured storage amount Y is equal to or less than the second set total flow amount B, it is further determined whether the measured storage amount Y is equal to or smaller than the first set storage amount R (Y ≦ R?), When it is determined that the storage amount is equal to or less than the first set storage amount R, the drive control of only the first pump 15 is performed assuming that the leakage flow rate is considerably large but the storage leakage amount is small, but the measured storage amount Y is equal to the first set storage amount. When it is determined that R is larger than R (R <Y), the storage leakage amount is normal, but the leakage flow rate is considerably large, and the first and second pumps 15 and 16 are respectively driven and controlled. Then, pumping amount control corresponding to a large amount of water leakage is performed.
[0015]
On the other hand, in the present embodiment, when it is determined that the total leaked flow X is larger than the second set total flow B, it is determined that this is an abnormal leak, and the drive control of the first and second pumps 15 and 16 is performed. In addition to the above, a control to display a message to that effect or to emit a buzzer to notify the user is performed, and control corresponding to abnormal water leakage is performed in this manner. By the way, it is needless to say that control can be performed such that a large amount of water is pumped out by driving an emergency pump separately provided for such abnormal water leakage.
[0016]
As described above, the embodiment of the present invention measures the electrode for electric conductivity measurement, which is hardly affected even if the water leakage flow rate in the underground structure is continuously immersed in the seawater-containing leakage water. Input the measured value of the electric conductivity continuously obtained by installing it on the site, calculate the leakage flow rate based on this, and determine the amount of pumped water based on the calculation result (first and second in the previous embodiment). The drive-stop control of the two pumps 15 and 16) is performed, and the control can be performed, so that the leakage pumping management in the underground structure can be reliably and easily performed. By the way, it goes without saying that the above-described control of pumping out water leakage is not limited to the installation of a plurality of pumps, and can be carried out by using a pump of variable pumping capacity.
[0017]
In addition, in this embodiment, since the water leakage pumping control based on the continuous input of the water leakage flow rate can be performed without requiring any manpower, the efficiency of the operation can be greatly increased, and the operation can be performed at a plurality of calculated positions. Since the control of pumping out water can be performed based on the flow rate of water leaking at the time, the accuracy is improved.
[0018]
Still further, the water leakage calculating device of the present invention can be provided as a portable handy type device instead of the above-described device. FIG. 12 shows a schematic diagram of this. The calculating device 17 has a microcomputer provided with a storage unit as a control unit 18, and the storage unit stores water at each of the measurement positions (a) to (i). A relational expression between the quantity and the electric conductivity is input. Further, the control section 18 is provided with a switching operation tool 19 capable of selectively switching each of the measurement positions, and is connected to an electrode 20 for measuring electric conductivity. Then, when the operator goes to an appropriate measurement position with the calculation device 17, and immerses the electrode 20 directly in the water leak while measuring the electric conductivity while selecting the measurement position, the measured value is transmitted to the control unit 18. The leakage flow rate is calculated by inputting the measured value into the relational expression. It is needless to say that the calculated water leakage flow rate can be displayed on the display unit 21 and the leakage water flow rate value or the measured value of the electric conductivity can be registered and inputted to a personal computer provided separately. No.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a submarine tunnel.
FIG. 2 is a graph showing the relationship between the sodium ion concentration of water leakage and electric conductivity.
FIG. 3 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (a).
FIG. 4 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (b).
FIG. 5 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (c).
FIG. 6 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (d).
FIG. 7 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (e).
FIG. 8 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (f).
FIG. 9 is a graph showing a relationship between a water leakage flow rate and an electric conductivity at a measurement position (g).
FIG. 10 is a sectional view schematically showing a water leakage pumping device.
FIG. 11 is a flowchart illustrating an example of leakage water pumping control.
FIG. 12 is a schematic perspective view showing a handy type water leakage flow rate calculating device.
[Explanation of symbols]
5 Leakage flow rate calculating device 8 Control unit 9 Calculating means 11 Determining means 12 Electrode 13 for measuring electric conductivity Pump unit 14 Storage leak detecting sensor 15 First pump 16 Second pump 17 Leakage calculating device 20 For measuring electric conductivity electrode

Claims (8)

The flow rate of the leak containing seawater in the groundwater was calculated as a function of the relationship between the flow rate of the leak and the electric conductivity, and the measured electric conductivity of the leak was substituted into the function. A method for calculating the flow rate of leaked water containing seawater in groundwater. In calculating the flow rate of the leak containing seawater in the groundwater, a means for functionalizing the relationship between the leak rate and the electrical conductivity, and substituting the measured value of the electrical conductivity of the leak into the functioned one. Means for calculating a flow rate of water leakage. A flow rate calculation apparatus for water leakage containing seawater in groundwater. The flow rate calculating method or the flow rate calculating apparatus according to claim 1, wherein the relationship between the flow rate of the leaked water and the electric conductivity is a linear function. 4. The flow rate calculating method or flow rate calculating apparatus according to claim 3, wherein the linear function is obtained from a measured value of a flow rate and an electrical conductivity of the leaked water. 4. The groundwater according to claim 3, wherein the linear function is obtained by correcting a measured value of the flow rate of the leaked water and the concentration of the component derived from seawater by a relational expression between the concentration of the component derived from seawater and the electric conductivity. Calculation method or flow rate calculation device for water leakage including seawater. In configuring a control device for pumping water leakage, comprising a pump means for pumping leakage water including seawater into the underground water from the underground structure, and a control means for controlling the pumping amount of the pump means, the control means includes: Input means for inputting the measured value of the electric conductivity of the leak, and applying the measured value of the input electric conductivity to the function formula obtained because the flow rate of the leak water and the electric conductivity measured in advance are obtained. And a determining means for determining a pumping amount of the pump means based on the leaked water flow rate. In claim 6, the control device is connected to an electrode for measuring electric conductivity, which is set at an arbitrary measuring position having a preset water leak, and inputs a measured value of electric conductivity measured at the electrode. A control device for the amount of pumped water leaked, characterized in that: In claim 7, a plurality of measurement positions are set, and a total leakage flow rate is calculated by adding the leakage flow rates calculated from the respective measured values of the electrical conductivity at the plurality of measurement positions, and based on the total leakage flow rate. A control device for controlling the amount of pumped water for leakage, wherein the controller determines the amount of pumped water.

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