JP2677984B2 - Water level control method for waterway system - Google Patents

Description

The present invention relates to a water channel system having a water storage means such as a tank, a dam, and a weir, and a water conduit for supplying water to the water storage means so that the water level of the water storage means becomes a target water level. The present invention relates to a water level control method for a water channel system for controlling the amount of water discharged from the water channel system, and in particular based on parameters obtained by analyzing as a water channel system two tank model having a water storage means and a water conduit for supplying water to the water storage means. The present invention relates to a water level control method for a water channel system for controlling the water discharge amount. As one of the methods of effectively utilizing the water resources of the water storage means such as the tank, the dam, and the weir, there is a method in which the water discharge amount of the water channel system is controlled to keep the water level of the water channel system constant. FIG. 1 is a block diagram showing an example of the configuration of a water level control device that controls such water discharge amount. In this figure, 1 is a head tank, and the water supplied through a water conduit 2 is temporarily stored in this head tank 1 and then, when the operating valve 3 is opened, water is discharged through a water discharge channel 4. To rotate the generator 5. Further, 6 is a deviation detector for detecting the water level deviation of the head tank 1. This deviation detector 6 compares the output (signal S ₂ ) of the water level detector 7a with the water level set value signal S ₁ to determine the water level deviation e. Obtained and supplied to the control device 7. The control device 7 controls the operation valve 3 based on the water level deviation e so that the water level in the head tank 1 becomes the target water level. By the way, in such a water level controller, an empirically obtained formula such as “PI control” or “ke ⁿ (k, n is a constant)” is used when the water discharge amount QO is obtained from the water level deviation e. Therefore, the inflow QI, which is a disturbance, is not directly considered, and therefore the inflow due to the upstream dam discharge, etc.
There were inconveniences such as a control delay when the QI suddenly changed, the water level in the waterway system was out of the allowable range, and the number of times the operating valve was opened and closed increased. In view of the above points, the present invention keeps the water level of the water channel system (water storage means) within an allowable range without increasing the number of times the operation valve is opened and closed even when the amount of water supplied through the water conduit changes suddenly. A method for controlling the water level of a water channel system that can maintain the water level is provided by controlling the operation valve for water discharge so that the water level of the water supplied to the water storage means via the headrace becomes the target water level. In the water level control method for a water channel system for controlling a water channel system, the first virtual tank corresponding to the water storage means and the first water tank corresponding to the water channel are provided as a water channel system equivalent to the water channel system including the water channel and the water storage means. Constructing a virtual waterway system composed of a second virtual tank having a larger floor area than that of the first virtual tank and a virtual waterway for supplying water stored in the second virtual tank to the first virtual tank And the fluid resistance of the virtual channel A parameter R indicating the first
Parameter A ₁ indicating the floor area of the virtual tank of
The parameters A ₂ and A ₂ ′ indicating the floor area of the virtual tank are determined in advance from the response of the water level system, and among the factors that affect the water level change of the water storage means due to the change of the outflow rate QO from the water storage means. , The water level sampling time To is set to A ₁ R or more so that the parameter R can replace the factor involved in the delay time from the change of the outflow flow rate QO to the change of the water level of the water storage means. During the sampling time To, when the water level of the water storage means is above or below a predetermined range δh from the target water level, the water level change value Δh during the sampling is held and the outflow flow rate QO from the water storage means is ± δh. / R only increases or decreases, when the change in water level caused by the predetermined period has elapsed T _BD = a ₂ · R reaches a predetermined range value ± .delta.h water level rise to it, the outflow rate QO (δh / R + Δh · a 2 ′ / To) Increase or decrease It is characterized by that. An embodiment of the present invention will be described below with reference to the drawings. First, prior to the description of the water level control method for a water channel system according to the present invention, first, a long open channel (headrace channel 2) as shown in FIG.
2) and a water storage means (corresponding to the head tank 1) are modeled as an indefinite flow equation model represented by simultaneous partial differential equations, and the outflow from the above-mentioned channel system. With the flow rate as QO and the inflow rate into the above-mentioned water channel system as QI, the results of simulating changes in the water level of the headrace 2 when these flow rates are changed will be described. Figure 2 shows the outflow rate QO in such a model.
It is a figure which shows the water level response waveform at the time of changing suddenly (the simulation result), and FIG. 3 is a figure which shows the calculation point of the water level shown in FIG. The water level response waveform obtained by the simulation shows that the head tank when the operating valve 3 is suddenly opened to suddenly change the outflow rate in the actual water channel system having the same configuration as the water channel system shown in FIG. It also matches well with the water level response waveform of 1. Further, in FIG. 2, the solid line L ₁ shows the water level response waveform at the downstream side point No. ₁ of the headrace 2a. Here, the downstream-side point No. 1 is the point closest to the head tank 1, and can be considered to approximately coincide with the point of the head tank 1. Therefore, it can be said that the solid line L _{1 in} FIG. 2 indicates the water level response waveform of the head tank 1. Then, when the outflow rate QO is suddenly changed as shown by the solid line L ₁ , the water level at the downstream side point No. 1 is suddenly changed from the sudden change start time (t = 0) for a predetermined period (t = 0 to t1), and is changed to a predetermined value. After the lapse of the period (after t = t1), it changes with a predetermined inclination. In addition, the water level of No. 2 and No. 3 on the upstream side of point No. 1 is also a solid line.
As shown in L ₂ and L ₃ , it changes similarly to the water level at No. 1 point mentioned above. On the other hand, although not shown, in such a model, when the inflow flow rate QI is suddenly changed, until a predetermined period elapses from the time when the inflow flow rate QI is suddenly changed,
The water level is kept almost constant, and the water storage changes after the predetermined period. Next, in the two-tank model, the change in water level when the outflow rate QO and the inflow rate QI are changed will be described. First, referring to FIG. 4, in the waterway system shown in FIG. 1, the head tank 1 is represented by an outflow side tank, and the headrace 2 (river system) which is a distributed constant system is an inflow side which is a lumped constant system. A two-tank model represented by a tank and a water channel connecting the outflow side tank and the inflow side tank will be briefly described. As shown in this figure, the water supplied through the water channel a is temporarily stored in the inflow side tank 1a corresponding to the water channel 2, and then the water channel 1c provided in the lower part of the inflow side tank 1a is stored. It is supplied to the outflow side tank 1b via the. And this outflow side tank 1b
The water stored in is discharged through the discharge channel 4b. Here, if the water level of such a two tank model is expressed by a differential equation, Becomes However, H ₁ is the water level of the outflow side tank 1b, H ₂ is the water level of the inflow side tank 1a, A ₁ is a parameter indicating the floor area of the outflow side tank 1b, A ₂ is a parameter indicating the floor area of the inflow side tank 1a, R is a parameter indicating the resistance of the water channel 1c, T ₁ (T ₁ = A ₁ ·
R) is a parameter indicating a response delay, and T ₂ (T ₂ = A ₂ · R) is a parameter indicating a control operation period described later. In general, since the headrace 2 is long and it can be assumed that A ₂ >> A ₁ , if the inflow flow rate QI and the outflow flow rate QO are changed stepwise in these equations (1) and (2), Is obtained. However, h ₁ indicates the amount of change in the canal of the outflow tank 1 _b . And in this equation (3), the outflow rate
If QO is changed stepwise, the water level change response waveform shown in FIG. 5 can be obtained. As shown in this figure, at time t ₀ , if the outflow flow rate QO (see (c) in the figure) is changed by ΔQO, the water level H ₁ of the outflow side tank 1b (see (b) in the figure) changes from time t _0. Until the period Ta elapses, the slope Δha / Ta changes rapidly, and thereafter the slope Δhb / Tb changes slowly. If the outflow rate QO is kept constant and the inflow rate QI is changed stepwise, the water level response waveform shown in FIG. 6 is obtained. As shown in this figure, at time t ₁ , the inflow flow rate QI
(See (b) in the figure), the water level H _{1 in the} outflow side tank 1b (see (b) in the figure) changes slowly with a slope Δhc / T _D after a lapse of the period Tc from time t _1. To do. Next, each parameter of the two-tank model will be further described with reference to the equation (3) and the water level response waveforms shown in FIGS. 5 and 6. First, in equation (3) above, the inflow flow rate QI
If the outflow rate QO is changed, the water level change h ₁ (t) at this time is Can be expressed by Then, as is clear from the equation (4) and the water level response waveform shown in FIG. 5, the parameters R and A ₂ are Since the parameter T ₁ indicates the water level recovery delay period when the outflow rate QO suddenly changes, it can be expressed as T ₁ = Ta (7). Further, in the above formula (1), T ₁
= A ₁ · R, so the parameter A ₁ is Can be expressed by Next, in the equation (3), the water level change h ₁ (t) when the outflow rate QO is kept constant and only the inflow rate QI is changed is It is represented by the following formula. From this equation (9) and the water level response waveform shown in FIG. 6, the parameter A ₂ is Can be expressed by Meanwhile, since the parameter A ₂ shown in (10) to the parameter A ₂ shown (6), not generally equal, replacing the parameters A ₂ shown in (10) and the parameter A _'2, where If we newly define this equation (10), Is obtained. Further, if the term of ΔQI in the equation (3) is shown by the parameter A ′ ₂ shown in the equation (10) ′, the equation (3) becomes Becomes The above A ′ _{2 is} also a parameter indicating the floor area of the inflow tank 1a. 4 Next, in the water level response waveforms shown in FIGS. 5 (a) and 6 (a), and the water level response waveforms shown in FIG. 2 obtained by modeling the water channel system of FIG. Although there is a difference that the vertical axes of both graphs show the water level of the head tank 1 in FIGS. 5 and 6 (a) and the water level decrease amount of the head tank 1 in FIG. taking into consideration the points as apparent from comparison therebetween, if obtained by a sudden change of the outflow rate QO when t = 0 in Figure 2, surge decrease in the water level up to t = t ₁ (i.e., water level rapidly decreases On the other hand, in FIG. 5 (a), when the outflow rate QO is changed at time t ₀ , the water level sharply decreases until the period Ta elapses, and in FIG. 2, t = t ₁
After that, the amount of decrease in the water level increased at a constant rate,
5 (b) also a time after t ₀ In can be seen that the water level is gradually decreased at a constant rate. Although not shown in the figure where the inflow flow rate QI is suddenly changed in the case where the water channel system of FIG. 1 is modeled with an indefinite flow equation, the head tank 1 is operated until a predetermined period elapses from the time when the inflow flow rate QI is suddenly changed. It has already been mentioned that the water level in the area is kept almost constant, and the water level changes after this predetermined period. On the other hand, in the water level response waveform shown in FIG. 6 (a), when the inflow flow rate QI is suddenly changed at time t ₁ , the water level in the head tank 1 becomes constant until the period Tc elapses, and the period Tc is After the passage of time, the water level has changed,
The characteristics are the same as when using the non-constant flow equation model. Thus, the water level response waveforms of FIG. 1 and FIG. 5 (a) showing the water level response waveform of the water channel system are similar in shape, and both water level response waveforms are almost the same. Can be considered From this, the response characteristic of the water level H of the water channel system shown in FIG. ₁ can be equivalently expressed by the response characteristic of the water level H ₁ of the outflow side tank 1b in the two tank model shown in FIG. Furthermore, in an actual waterway system having the same configuration as the waterway system shown in Fig. 1, the outflow flow rate and the inflow flow rate are suddenly changed and the water level response waveform is measured, and the resulting numerical values Ta, Tb, TD, Δha are measured. , Δhb, ΔQO, ΔQI, and the equations (5) to (10) ′, the values of the parameters R, A ₂ , A ′ ₂ , and A ₁ of the two-tank model can be obtained. Hereinafter, the water level response characteristics of the water channel system shown in FIG. 1 will be considered using this two tank model. First, if the time Tc (see FIG. 6) is replaced by the time delay constant γ ₀ , the water level change h ₁ (t) in the above equation (3) ′ becomes Becomes Then, Laplace transform of this equation (11) and extracting only the transfer function from the result, Is obtained, and the block diagram shown in FIG. 7 is obtained by plotting this. In FIG. 7, 8 is a dead time element involved in the delay time (dead time) from the change of the inflow flow rate QI to the change of the water level, and 9 is a constant element related only to the time constant. The change amount ΔQI of the flow rate QI is converted by the dead time element 8 and the constant element 9 and then added to the outflow flow rate change amount −ΔQO at the addition point 10 to be integrated.
Supplied to 11. The integration element 11 is involved in integration of the deviation between the inflow flow rate change ΔQI and the outflow flow rate change ΔQO, and the output of this integration element is supplied to the addition point 12. Further, 13 is a code conversion element, and this code conversion element 13 inverts the outflow flow rate change amount ΔQO to add point 10 and delay element 14
To supply. The delay element 14 is involved in the delay time from the change of the outflow flow rate QO to the change of the water level,
The output of this delay element 14 is the integration element at the addition point 12
It is added to the output of 11 and output as the water level h. As described above, since the response characteristic of this water channel system includes the integral element 14, if it is controlled continuously, the control algorithm becomes complicated. Therefore, in the present invention, the period T ₀ is provided as the sampling period of the water level H to eliminate such inconvenience. The sampling period T ₀ will be described in detail below. First, the delay element 14 shown in FIG. Can be replaced with a constant R after a sufficient time has elapsed, so the sampling period T ₀ is set to a length that allows such replacement, for example, a length that is several times the time constant T ₁ . On the other hand, if the sampling period T ₀ is too long, the water level will be exceeded due to the detection delay. Therefore, the water level rise based on the inflow flow rate change ΔQI described above will occur. In consideration of the water level rise in the sampling period T ₀ Is set to be within the allowable value of the water level rise. That is, this sampling time T ₀ is To be a constant R, and Is set within the allowable water level rise value. Hereinafter, the above-mentioned parameters R to T ₂ and the sampling period T ₀
An embodiment of the present invention using is described. FIG. 8 is a block diagram of a water channel system to which the water level control method for the water channel system according to the present invention is applied. In this figure, reference numeral 15 is a transmission element showing the transmissibility of the water channel portion consisting of the headrace channel 2, the head tank 1 and the discharge channel 4 shown in FIG. 1, and this transmission element 15 is a delay element 8, a constant element 9, 14a, Integral element 11,
It is composed of addition points 10 and 12. Further, 16 is a control element for controlling the outflow rate QO of the water channel system, and this control element 16 is an addition point 17, an outflow rate control element (digital type controller) 18,
It is composed of a sampler 20 and a hold element 19. next,
The addition point 17 to the hold element 19 will be sequentially described. First, at the addition point 17, the value indicated by the water level setting command h ₀ is compared with the actual water level h to obtain a water level deviation and the result is supplied to the outflow flow rate control element 18. Here, prior to the explanation of the function of the outflow rate control element 18, the corrected flow rate ΔQO _A , ΔQ of the outflow rate control element 18 is explained.
A method of calculating O _B and the correction operation period T _BD will be described. First, the response waveform in the transmission element 15 of the block diagram shown in FIG. 8 (the water conduit 2, head tank 1,
Corresponds to the water level response waveform waterways consisting spillway 4), for example, as shown in FIG. 9, the inflow rate QI at time t _1a,
Assuming that the outflow rate QO does not change, and the value of the output (second water level change component) x ₂ of the integration element 11 at this time is δh and the value of the water level setting command h ₀ is zero, the time t _1a The output (outflow flow rate correction value) ΔQO of the control element 16 at ΔQO = −δh · m (13), so the output of the constant element 14a at this time (first
The water level component) x _1, the second values of the water level component x ₂ are each a _{x 1 = -R · δh · m} ...... (14) x 2 = δh ...... (15). Where m is the gain of the control element 16. Next, when sufficient time has passed from this time t _1a to time t _2a , these first and second water level change components x ₁ and x ₂ are respectively x ₁ = −R · δh · m ( 16) Becomes However, T is the period from time t _1a to time t _2a . Here, if the allowable range of the water level is δh, the first and second
The control conditions for the water level change components x ₁ and x ₂ of the equation are x ₁ + x ₂ ≧ −δh (18). By substituting the equations (16) and (17) into this equation (18), Is obtained. On the other hand, at the time t _2a , if the termination condition that makes the water level displacement zero when the outflow rate change ΔQO is zero is used, from the equation (17), From this equation (20) and equation (19), the gain m is Becomes Therefore, if the gain m is 1 / R, the corrected flow rate ΔQO _A (corrected flow rate in the correction operation period T _BD ) is Becomes Further, if the gain m is eliminated from the equations (19) and (20), the period T becomes T ≧ A ₂ · R (23). Therefore, the correction operation period T _BD becomes T _BD = A ₂ · R (24). Furthermore, in order to reduce the water level change after the end of this correction operation period T _BD to zero, Since it is necessary to satisfy the following expression, if the output of the integral element 11 whose output is a function of time t is differentiated with respect to time t, Is obtained. That is, if the change ΔQI in the inflow flow rate and the change ΔQO in the outflow flow rate are matched, the change in the water level after the end of the correction operation period T _BD can be zero. Here, in order to obtain the change ΔQI of the inflow rate, if the above equation (10) is rearranged, Is obtained. Therefore, if this period T _D is made to coincide with the sampling period T ₀ and the water level change during this sampling period T ₀ is Δh, the corrected flow rate ΔQO _B after the end of the correction operation period T _BD is Becomes Therefore, the outflow control element 18 controls the outflow when the water level during sampling rises from the target water level by δh.
QO, Flow rate QO when the correction operation period T _BD (T _BD = A ₂ · R) has elapsed from the sampling time.
To Just fix it. In addition, the outflow rate control element 18 is configured so that when the water level at the time of sampling falls from the target water level by δh,
Outflow QO Flow rate QO when the correction operation period T _BD has elapsed. Just fix it. The outflow rate correction value ΔQO obtained by the outflow rate control element 18 is held by the hold element 19. Next, the water level control operation according to the block diagram of the water channel system shown in FIG. 8 will be described with reference to FIGS. 10 and 11. FIG. 10 is a graph showing changes in each parameter during the water level control operation of the block diagram of the water channel system shown in FIG. 8, where (a) is the number of samplings, (b) is the water level of the head tank 1, ( C) is the correction value of the outflow rate,
(D) is the amount of increase / decrease of the outflow flow rate correction value in (c),
It is a graph which shows each change. Also, FIG.
It is a flowchart which shows the procedure of the water level control operation | movement in the block diagram of the water channel system shown in the figure. First, the time shown in Fig. 10
When the system is started at t _1D (step SP1 in FIG. 11), at this time t _1D , the water level H of the head tank 1 (see FIG. 1) is detected and the water level H is filtered ( At step SP2 in FIG. 11, the initial setting is performed at step SP3, and then step S2 is performed.
Go to P4. Here, since the elapsed time T from the time t _1D is zero, the step SP5 and the step SP6 are used to execute the step SP.
Based on 2. After that, steps SP2, SP4 to SP6 are repeatedly executed. Next, at time t _2D shown in FIG. 10, step SP4
Since T ≧ T ₀ at the time, the correction value ΔQO of the outflow rate QO and the water level deviation ΔH from the set water level are obtained at the next step SP7. Further, in this step SP7, the stored water level H ₁ is updated, the period T is cleared to zero, and the process proceeds to the next step SP8 to determine whether or not the water level deviation ΔH exceeds the allowable range of water level δh. To be determined. If the water level H exceeds the water level allowable value δh as shown in Fig. 10 (b), the step SP
Proceeding to 9, it is judged whether or not the value of the sampling number C ₁ is zero. In this case, since C ₁ = 0, step SP10 is executed, and the outflow rate QO up to that point is the outflow rate change amount. Only be increased. As a result, the outflow rate control element 18 increases the outflow rate QO by the flow rate ΔQO as shown in FIG. 10 (d), and this flow rate ΔQO is held by the hold element 19 as shown in FIG. 10 (c). . As a result, the water level H of the head tank 1 is lowered as shown in FIG. Then, in the next step SP11, the value of the sampling number C ₁ is incremented, and thereafter, the value is derived from step S ₂ via steps SP12 and SP6. Below steps SP2, SP4, SP
5, the value of the period T is updated every time SP6 is executed, and each time the value of the period T exceeds the sampling period T ₀ , steps SP4, SP7, SP8, SP9, SP13 to SP17, SP11,
SP12 and SP6 are executed and the value of the sampling count C ₁ is updated. Then, when the period T _BD elapses from the time t _2D and the value of the sampling number C ₁ becomes 4, the step SP13 to the step SP13 are performed.
Proceed to SP18, the outflow QO is a correction value Only be reduced. As a result, the outflow rate control element 18 determines the outflow rate QO as shown in Fig. 10 (d). Only decrease. As a result, the water level H of the head tank 1 is restored to the set water level h ₀ as shown in FIG. Then, at the next step SP11, the value of the sampling number C ₁ is incremented, and thereafter, the value is obtained from the step SP2 via the steps SP12 and SP6. Next, a transition period T _CD (this transition period T _CD has the same length as one sampling period T ₀ ) elapses from the time t _3D , and the number of sampling times is changed in step SP11.
When the value of C ₁ is incremented to the value 6, the step
The number of samplings C ₁ is zero-cleared through SP12, SP19, and SP6, and thereafter, it is returned to the initial state by being returned to step SP2. Further, at the time of sampling, when the water level H of the head tank 1 is lower than the allowable range −δh on the low water level side, steps SP20 to SP25 are executed instead of the steps SP9 to SP12, SP18 and SP19 described above, and the water level Corrections are made. As described above, in the water level control method for a water channel system according to the present invention, the first virtual tank corresponding to the water storage means and the water channel are provided as a water channel system equivalent to the water channel system including the water channel and the water storage means. A corresponding second virtual tank having a larger floor area than the first virtual tank; and a virtual water channel for supplying water stored in the second virtual tank to the first virtual tank. And a parameter indicating the floor area of the second virtual tank, a parameter indicating the fluid resistance of the virtual water channel, and a sampling period and previously determined, and each of the parameters, sampling period, and predetermined Based on the correction dead zone and the water level change in the sampling period in the first virtual tank, the water discharge flow rate correction value is calculated, and based on this water discharge flow rate correction value Since the discharge flow rate up to that point has been corrected, the flow of water in the headrace can be treated in a lumped constant manner, and this allows the water storage means to be operated when there is a sudden change in the flow rate into the water storage means. Analysis of changes in water level is simplified, and it becomes possible to perform water level control that takes into account the inflow that was a disturbance in conventional water level control devices. Therefore, even when the amount of water supplied through the headrace changes suddenly, the water level of the waterway system (water storage means) can be kept within an allowable range without increasing the number of times the operation valve is opened and closed. Since the time control algorithm is very simple, the water level can be controlled by a simple circuit configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example of a water channel system consisting of a long open channel and a head tank, and FIG. 2 is a water level response waveform when the water channel system shown in FIG. 1 is modeled by an indeterminate flow equation. Figure 2 and Figure 3 are second
The figure which shows the calculation point of the water level shown in the figure, FIG. 4 is the figure which shows a two tank model, FIG. 5 and FIG. 6 are the figures which respectively show the water level response waveform of the two tank model shown in FIG. 4, and FIG. Is a block diagram showing the transfer characteristics when the water channel system shown in FIG. 1 is modeled by two tanks, and FIG. 8 is a block diagram for explaining one embodiment of the water level control method of the water channel system according to the present invention. FIG. 10 is a waveform diagram for explaining a method for calculating a corrected flow rate and a correction operation period in the same water level control method, FIG. 10 is a waveform diagram for explaining the same embodiment, and FIG. 11 is a description for the same embodiment. It is a flow chart for. 8 ... Delay element, 9 ... Constant element, 11 ... Integral element, 14
a …… Constant element, 15 …… Transfer element, 17 …… Addition point, 18…
Outflow control element, 19 Hold element.

Claims (1)

(57) [Claims] In a water level control method of a water channel system, which controls the water level by controlling an operation valve for water discharge so that the water level of the water supplied to the water storage means via the water channel reaches a target water level, the water channel and the water storage means And a second virtual tank having a larger floor area than the first virtual tank corresponding to the water storage channel and the first virtual tank corresponding to the water conduit. A virtual waterway system comprising a tank and a virtual waterway that supplies water stored in the second virtual tank to the first virtual tank, and a parameter R indicating fluid resistance of the virtual waterway, and The parameter A ₁ indicating the floor area of the _first virtual tank and the parameters A ₂ and A ₂ ′ indicating the floor area of the second virtual tank are obtained in advance from the response of the water level system, and the outflow rate from the water storage means is determined. Due to changes in QO Among the factors affecting the level change of the serial reservoir means, said outflow rate QO
The sampling time To of the water level is set to A ₁ R or more so that the factor involved in the delay time from the change of the water level to the change of the water level of the water storage means can be replaced with the parameter R, and during this sampling time To When the water level of the water storage means is above or below a predetermined range δh from the target water level, the water level change value Δh during the sampling is held and the outflow flow rate QO from the water storage means is increased or decreased by ± δh / R. , The change in the water level caused by it is the predetermined range value of the water level rise ±
A water level control method for a water channel system, wherein the outflow flow rate QO is increased or decreased by (δh / R + Δh · A ₂ ′ / To) when a predetermined period T _BD = A ₂ · R reaching δh has elapsed.