JPS6062316A - Automatic water level control method and apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an automatic water level adjustment method and device that can automatically adjust the water level in a reservoir or a river, and more particularly, to Existing conventional construction that corresponds to the height of the spillway by making maximum use of the design plan overflow water depth while overflowing the design plan flood volume as per the design plan without increasing the height of the spillway. The present invention relates to an automatic water level adjustment method and device capable of storing a water storage amount greater than the full water level storage amount, that is, the maximum possible storage amount for a design plan overflow water depth.

[Conventional technology] Conventionally, reservoirs have been flooded with spillways so that water above a certain water level can be discharged.Limiting the storage of water within the height of such spillways has a negative impact on natural water resources. Unfortunately, this results in people simply throwing it away without making full use of it. However, in the current reservoir facility, it is possible to store more water than the current storage capacity if the conditions are such that the overflow does not cause damage to the design plan overflow depth.

Conventionally, the following methods have been used to raise the water level of a reservoir. In other words, in order to increase the height of the spillway, (a) 1. Method of raising the height using barbs and planks, (b) Method of installing a rubber dam (DAM), (c) Method of installing a tenter gate. d) Siphon (Sy)
phon).

[Problems to be solved by the invention] However, in the case of (a) above, the shibo is washed away during floods, so it is necessary to reload the top of the pile every time it rains, which is not economical. There are disadvantages such as loss, consumption of manpower, and time consuming. In the case of (b), when a rubber dam floods, the rubber dam itself collapses and the flood volume increases beyond the designed flood volume, resulting in severe damage to the downstream spillway and river. In case (c), the flood gates must be opened and closed manually during floods, and if the flood gates are opened, the floodwaters will overflow all at once, causing enormous damage to the spillway and river. Not only is it inconvenient to have to report the flow rate to the dam at any time at the flow gauging station and operate the flood gates accordingly, but also because large dams have to set the winter high water level and summer high water level and adjust them in advance before a flood occurs. The frequency of opening and closing of the sluice gates is low, and on the other hand, small-scale dams cannot have a dam keeper, making it difficult to operate the sluice gates in an emergency. In the case of (d), a siphon is installed at the spillway, and when the water level rises above a certain level, the siphon is activated all at once, discharging a large amount of flood water, so the downstream spillway and river are flooded. The damage caused is great, and when the operation is corrected, the water level drops below the initial full water level, and there are drawbacks such as difficulties in construction and excessive construction costs. On the other hand, if the spillway itself is made higher, the full water level will be higher, but as the overflow water depth in the design plan increases, problems such as the construction of higher embankments and the expansion of submerged areas will arise.

Next, in the case of a person i living on a river, a fixed concrete 7-foot wall is constructed across the river to raise the water level of the weir and take water through the canal. Flood volumes are increasing in the area, leading to problems such as the risk of bank collapse and damage to riverbeds.

Therefore, the present invention aims to solve the above-mentioned problems of increasing the amount of water stored in the reservoir and regulating the water level of the weir in the river 1K. There is no need to expand the submerged area, and the amount of overflow water can be reduced according to the design plan, and at the same time, the amount of water stored at the previous full water level corresponding to the existing spillway can be increased. The object of the present invention is to provide an automatic water level adjustment method and device that can automatically adjust and secure the planned water storage level (changed full water level) while storing water.

[Means for Solving the Problems] According to the present invention, a water gate is installed above the spillway of a reservoir to store water at a modified full water level higher than the spillway, and a float is installed at the modified full water level. The water gate is opened and closed in response to the rise and fall of the float, and the operation of the water gate is controlled in response to the rise and fall of the float as the water level changes from the changed full water level to the design plan overflow water level. The value corresponding to the water depth from the above changed full water level to the design plan overflow water level vs. the sum of the water depth from the spillway to the design plan overflow water level and the water depth from the design plan overflow water level to the abnormal flood level. An automatic water level adjustment method is provided that is set to a value that Further, according to the present invention, a water gate is installed on a river bed, a float is floated at the weir water level of the river, and the water gate is opened and closed in response to the rise and fall of the float, so that the designed floodwaters are flooded from the weir water level. The operating ratio of the water gate with respect to the rise and fall of the float as the water level fluctuates from the weir water level to the design flood level versus the value equivalent to the water depth from the river bed to the design flood level. An automatic water level adjustment method is provided. Further, according to the present invention, the spillway includes a water gate installed on the river bed so as to be able to move up and down, a float suspended at a changed full water level or weir water level due to the installation of the water gate, and the float and the water gate. There is provided an automatic water level adjustment device comprising a driving means which is interlocked and connected to each other and opens and closes the water gate in response to the raising and lowering of the float.

[Function] By providing the automatic water level adjustment method and its device, when flood water flows into a reservoir or river and the water level becomes higher than the changed full water level or the weir water level, the float rises, and the float rises. In response, the drive is actuated to pull the sluice gate open and automatically discharge the incoming water volume to maintain the water level in the reservoir or river at a modified full or weir level.

〔Example〕

Next, the automatic water level adjustment method and device according to the present invention will be explained based on illustrated embodiments.

FIG. 1 shows the principle of the method of the invention applied to a reservoir. In the figure, P is the reservoir, Q is the spillway, and R
is a water flow guide stand installed at the same height as the spillway Q, S
is a gutter. The full water level of such a reservoir is Dz (hereinafter referred to as the previous full water level). This previous high water level DI
In order to further increase the amount of water stored, a water gate l is installed on the water flow guide stand R, thereby making it possible to set the changed full water level to Dz. If water flows into the reservoir P bag above this changed full water level D2, that amount of water will be discharged from the reservoir P,
A float 2 floats between the changed full water level D2 and the design plan overflow water level D3 according to the water level of the reservoir P in order to open and close the water gate l to automatically adjust the water level of the reservoir P to the changed full water level D2. At the same time, a drive means 3, which will be described later, opens and closes the water gate 1 in response to the -L movement of the float 2. , the water level becomes higher than the changed full water position D2,
When the float 2 rises -E, the driving means 3 pulls the water gate 1 -E to open in accordance with the water depth H9, and discharges an amount of water corresponding to the amount of inflow water.At this time, If the discharge amount is greater than the inflow amount, the water level gradually decreases and the float 2 descends accordingly, causing the drive means 3
The sluice gate is lowered and closed. Furthermore, when the water gate l is closed, the water level rises again, the float 2 rises, and the water gate l is opened again as described above.The opening and closing operations of the water gate corresponding to the position of the float 2 are repeated, and the The water level is automatically adjusted to maintain the full water level D2.

Here, the relationship between the lifting and lowering of the float 2 and the operation of the water gate 1 will be explained.

Float 2 changes from full water position D2 to design aI water level D3
In other words, it floats within the water level adjustment water depth H1, and the greater the water level adjustment water depth H1, the higher the adjustment accuracy becomes. The period from the changed full water level Dl to the design plan overflow water level D3, that is, the design plan overflow water depth H
2 is constant, increasing the water level adjustment water depth H will lower the changed full water level D2, so the water depth at which the water storage can be increased by installing the water gate l (previous full water level DI
The water depth (water depth from to the modified full water level D2) Hs becomes relatively small. Therefore, if the height of the modified full water level D2 is appropriately adjusted, the water level adjustment water depth H1 is also adjusted by the floating distance of the float 2 accordingly. That is, the following equation holds true.

Water depth H3 of the changed full water level D2 + Water depth for water level adjustment) 11 = Design plan overflow depth H2 On the other hand, the inflow φ of flood water flowing into the reservoir P has increased in the water gate 1, and the float 2 has reached the design plan overflow water level D3. When,
It is necessary to raise the water higher than the design plan overflow depth H2. In other words, the water gate l is the water depth between the design plan water depth H2 and the design plan overflow water level D3 to the abnormal legal water level D4 (abnormal flood water depth).
It is necessary to raise the water by an amount equivalent to the abnormal flood depth H5, which is the sum of H4 and H4. For example, when the design plan overflow water depth H2 is 1 m, the float 2 will rise by 1 m to the design plan overflow water level D3, but the opening/closing height of the water gate l must be higher than the design plan overflow water level D3. Design plan overflow water level DH
The water level must be 1.2 m or higher, which is the abnormal legal water level D4 plus 20% increase of (1 m). This is because if the opening/closing height of the flood gate I is below the design plan overflow water level D5, the water level will rise above the design plan overflow water level D5, causing problems such as the risk of bank destruction and expansion of the submerged area. is caused.

Therefore, by installing the water gate 1, it is necessary to determine the appropriate water depth H5 that can increase the amount of water stored, that is, to what extent the water level adjustment water depth H1 is determined.
The opening/closing ratio is determined.

In other words, the opening/closing ratio of the water gate l with respect to the vertical floating of the float 2 is changed from the water depth H1 (water level adjustment water depth) from the full water level D2 to the design plan overflow water level D3 versus the water depth H1 (water level adjustment water depth) from the spillway Q to the design plan overflow water level D3. Water depth H2 (design plan overflow water depth) and water depth H4 from the design plan overflow water level D5 to the abnormal legal water level D4
The value corresponding to the sum of By configuring the driving means 3 to operate the water gate 1 at a constant rate in response to the rise and fall of the float 2, it is possible to discharge the same amount of water for the amount of inflow water that is equal to or higher than the modified full water level D2. At the same time, when the water level of reservoir P reaches the design plan overflow water level D3, the position of flood gate 1 will be opened to the abnormal legal water level D4, which is higher than the design plan overflow water level D3. Since the water is discharged in the same condition as before, the flood volume can be discharged smoothly.

Here, the water depth H for water level adjustment and the opening/closing side of the water gate I will be illustrated.

The design plan overflow water depth H2 is 1 m, the abnormal legal water level D4 is 20% higher than the design plan overflow water level D3, and the abnormal flood water depth H5 is 1 m.
．． If it is 2m, the following is the water depth H for water level adjustment.
is set to 10 cm (water depth H31 + 90 cm, where water storage capacity can be increased by installing water gate l), then l of water gate l
I + incisor depth l±★ will be more than 12 times the samurai adjustment water depth H1. In other words, the opening/closing ratio of water level adjustment water depth H1 to water gate l is 1:1.
It becomes more than 2.

■If the water depth H1 for water level adjustment is 20 cm (H5 is 80 cm), the opening/closing height of the water gate l will be more than 6 times the water depth H for water level adjustment. That is, the water depth H for water level adjustment and the opening/closing ratio of the water gate are 1:6 or more.

■If the water depth H1 for water level adjustment is 30 cm (Hg is 70 cm), the opening/closing height of the water gate I will be more than four times the water depth H1 for water level adjustment. That is, the opening/closing ratio of the water level adjustment water depth H1 to the water bolt l is 1:4 or more.

■If the water depth H for water level adjustment is set to 50cm (H5 is 50cm), the opening/closing height of the water gate L will be approximately 2 times the water depth H1 for water level adjustment.
．． It will be more than 4 times more. That is, water depth H1 for water level adjustment vs. water gate l
The opening/closing ratio is l:2.4 or more.

Here, if the water level adjustment water depth H1 is too small, a large amount of water can be secured, but even slight fluctuations in water level (not water level fluctuations due to flow 1'r, but water surface fluctuations due to waves, etc.), the vertical movement of water gate l becomes large. On the other hand, if it is increased too much, the vertical movement of the water gate l will not be large, but the amount of water stored will be relatively small, so the minimum adjustment water depth H, is: Approximately 30% of the design plan overflow water depth H2 is suitable.

Therefore, when the height of the designed overflow water depth H2 is 1-m and the water level adjustment water depth H1 is 30 cm, the water gate 1 is opened by the driving means 3 to a height of 1.2 m or more, which is four times the height. That is, since the sluice gate I is located 1.2 m from the top of the spillway Q, the flood water is discharged while maintaining the original design plan overflow depth H2.

In this way, as the water level rises and falls, the opening and closing ratio of the water gate l is
Water depth H from the modified full water level D2 to the design plan overflow water level D3
1 (Water depth for water level adjustment) vs. sum of water depth H2 (design plan overflow water depth) from spillway Q to design plan overflow water level D3 and water depth H4 from the design plan overflow water level D3 to abnormal flood water level D4 We set the abnormal flood water depth H5 to be the value corresponding to
When the amount of inflow water exceeds the changed full water level D2, the water gate 1 is automatically opened and closed according to the water level, and the same amount of water as the amount of inflow water can be discharged, and the water in the reservoir P is maintained at the changed full water level D2. I can do it.

Next, the principle of the method of the present invention applied to river T will be explained based on FIG. 2.

A water gate l is installed on the riverbed U, and a float 2 is suspended at the weir water level D6, and according to the vertical movement of the float 2, the water gate l is opened and closed by the driving means 3, and the water gate l is opened and closed at the same rate for the amount of inflow water exceeding the weir water level D6. The water level of the river T is always maintained at the weir water level D6 by discharging the same amount of water.

Here, the operation of the water gate 1 in response to the raising and lowering of the float 2 will be explained.

The float 2 floats below -L between the weir water level D6 and the designed flood amount D7 (water level adjustment water depth H6).

On the other hand, when the inflow I11 of flood water flowing into the river T increases and the flood gate 1 reaches the design plan flood volume D7,
The operating means 3 is configured to be raised to a height corresponding to the designed flood water depth H7.

That is, the opening/closing ratio of the water gate l with respect to the rise and fall of the float 2 is:
Water depth H6 (from weir water level D6” to design plan flood volume D7)
The water depth H7 (design flood water depth) is set from the river bed U (water depth for water level adjustment) to the design flood volume D7, and the driving means 3 is configured to have this operating ratio.

Therefore, flood water flows into river T, and its water level becomes weir water level D6.
When the flow exceeds 2, the flow 2 rises, and the water gate 1 is pulled up and opened at the above-mentioned ratio to the rise of the float 2 via the drive means 3, and an amount of water corresponding to the amount of inflow water is discharged.

When the amount of discharge is greater than the amount of inflow, the water level gradually falls and the water gate I is lowered and closed by the driving means. When the water gate 1 is lowered and closed, the water level rises, and the water gate 1 is automatically lifted and opened again by the driving means. By repeating the raising and lowering movement, the weir water level D6
is automatically adjusted.

At this time, when the amount of inflow water gradually exceeds the amount of discharged water, the water level continues to rise even though water continues to be discharged, but the position of flood gate 1 when the design plan flood amount reaches D7 is the same as the design plan flood amount. By opening higher than D7, the designed flood volume will be discharged in the same manner as if the sluice l was not installed, so the flood volume can be removed smoothly. Here, as for the opening/closing height of the flood gate, the weir water level D6 is fixed in the river (therefore, the water level adjustment water depth H6 is fixed), so the ratio of the water level adjustment water depth H6 to the design flood depth H7 is Since the value is fixed, it can be set to a value suitable for the actual situation of the river. That is, for example, when the intake water depth H is 2 m and the water level adjustment water depth H6 is 5 m, the design plan flood water depth H
7 is 7 m, that is, the operating ratio of the float 2 and the water gate 1 should be 1:1.4. If this working ratio is 1:4 or higher as in the case of the reservoir,
Design plan: In the event of a flood, the floodgates will have to be raised by more than 20m, creating a contradiction in that the floodgates will be pulled up unnecessarily.
This creates the inconvenience of having to install something that is longer than 0m.

In this way, the float 2 is floated at the weir water level D6, and the operating ratio of the water gate 1 with respect to the rise and fall of the float 2 is set at the weir water level D6.
Water depth H's (water depth for water level adjustment) from to the design plan flood level D7 vs. water depth H7 from the river bed U to the design plan flood level D7
Since the drive means 3 is configured so that the amount of inflow water exceeds the weir water level D6, as the float 2 rises, the sluice gate 1 is pulled up and opened according to the operating ratio, and the amount of inflow water is increased. Since the same amount of water is discharged, the water level of the river T can always be maintained at the weir water level D6.

In Fig. 2, the days marked are abnormal flood levels.

Next, a specific example of the automatic water level adjustment device according to the present invention will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a side view showing the automatic water level adjustment device according to the present invention applied to a reservoir, and FIG. 4 is a perspective view of the device. As shown in FIG. 4, the sluice l installed on the flowing water guide stand R is installed on the flowing water guide stand R, and has rollers 12 on two guide rails 11 and 11 that have a U-shaped cross section and are arranged opposite to each other. .12 so that it can move up and down.

Above the sluice 1 a cradle 31.31' of the drive means 3 is arranged, which is supported by a column 9.9. The pedestal 31.
31' is formed into a rectangular parallelepiped by rail-like frame members 311 each having a U-shaped cross section, and three bearings 3 are mounted on the upper surface of the frame members 311.
21.322.323 and 321', 322', 32
3' are attached to each. The bearing 321.321'
has a shaft 33 each equipped with a chain wheel 33, 33'.
1.331' are each rotatably journalled. Also bearing 3
22, 322' has the chain wheel 33, 33'
A shaft 341.341' equipped with a chain wheel 34.34' of the same diameter and a large-diameter gear 35.35' each in one weight.
are each pivotably supported. Furthermore, bearing 323.32
3' is rotatably supported by shafts 361 and 361' each having a single weight of small diameter gears 36 and 36' and pulleys 37 and 37' which mesh with the large diameter gears 35 and 35'. Note that the large diameter gear 35, 35' and the small diameter gear 36.
When applied to a reservoir, the gear ratio with 36' is determined by the water depth H2 (designed overflow depth) from the top of the overflow Q to the design overflow water level D3 and the design overflow water level. D3
to the abnormal flood water depth H5, which is the value equivalent to the sum of the water depth H4 from 2000 to the abnormal flood level D4, to the water depth H1 (water level adjustment water depth) from the modified full water level D2 to the design plan overflow water level D3, and When applied to a river, the ratio is set as the water depth H7 (design flood water depth) from the river bed U to the design plan flood level D7 to the water depth H6 (water level adjustment water depth) from the intake water level D6 to the design plan flood level D7. This gear mechanism constitutes an amplification mechanism.

The float 2.2' has a cylindrical shape filled with a floating material having a low specific gravity, and is connected to the chain wheel 33,
A shaft rod 24 erected within the reservoir below 33'.
24', respectively. The float 2.2
Bearings are installed in the upper and lower parts of the hollow space 21 and 21', forming a shaft. In addition, mounting pieces '25 and 25' are respectively attached to the shaft rods 24 and 24' into which the float 2.2' is fitted, so that the vertical position can be adjusted, and the downward movement of the float 2.2' is restricted. are doing. A binding device 22.22' is attached to one end of each of the floats 2.2', and one end of a rope 4.4' is connected to each binding device 22.22'. One end of each chain 5.5' is connected to the other end of the rope 4.4', and the chain 5.5' engages with the chain wheels 33.33'' and 34.34' to connect the other end. are connected to ropes 7.7' which are connected to weights 6.6', respectively.

A fastening device 13.13' is attached to the upper end of the water gate l, and the pulley 37.
The ropes 8 and 8' each have one end connected to the rope 37', and the other end of each rope 8' is connected to the rope 37'. The weight of the weight 6.6' is the lifting load of the water gate l and the gears 35.35' and 36.3.
6' gear ratio (speed increasing ratio) and mechanical friction loss *Parable fjM? yLOQ'/F%I-kLl,
It is set larger than the sum of the weight of No. A 44Q6' and mechanical friction loss. In addition, the rope 8.8' connected to the water gate 1 is made to have a sufficient length so as not to be too tensioned so that the water gate 1 does not operate when the water surface flows due to waves.

The length L of the upper surface of the water guide platform H is set to an appropriate length to prevent the wood grain phenomenon in which the water flow X extends due to water pressure and falls directly into the gutter S (see Figure 1) when discharging flood water. Set to

Next, the operation of the above embodiment will be explained.

A water gate L is installed on the water flow guide platform R installed at the spillway Q of the reservoir P.
By installing this, the height of the spillway Q can be increased, and water can be stored at the changed full water level D2. When the water level of the reservoir P rises above the changed full water level D2 during a flood, the float 6.6' rises along the shaft 24.24', and the float 6.6', the rope 4.4', and the chain 5.5 ' and a weight 6.6' connected by a rope 7.7' is lowered. In this process, the chain 5.5' moves the chain wheel 34 (34') to the third
Since it rotates in the direction of the arrow in the figure, the large-diameter gear 35 is integrally formed with the chain wheel 34 (3° 4').
(35') are rotated in the same direction. Therefore, the small diameter gear 36 (35') meshing with the large diameter gear 35 (35')
36') rotates in the direction of the arrow, and the small diameter gear 36 (36'
) and the pulley 37 (37') rotate in the same direction, the ropes 8, (8') are wound around the pulleys 37, (37'), and as a result, the water gate l
is pulled up along the guide rail 11.11' (see Figure 4), and the water gate l is opened. Note that the weights 28 and 28' are heavier than the weight of the water gate l, so the float 6
．． 6' floats up due to buoyancy, and the water gate l is pulled up by the gravity of the weights 28 and 28'. Also,
When the gear ratio of the large gear 35 (35') and the small gear 36 (36') is set to 4:1, for example, the water level is 10 cm.
When it rises, float 2.2' rises 10 cm and 1 weight 6
．． 6' is lowered by 10cm.

The water gate 1 can be raised by 40 cm, which is four times the height due to the gear ratio. In other words, the water gate 1 will be raised at a rate four times greater than the water level rise.

When the water level of the reservoir P falls by opening the water gate L, the float 2.2' falls, but since the weight of the float is heavier than the weight of the weight 6.6', the weight 6.6' rises. The chain 5 connected to the weight 6.6' rotates the chain wheel 34.34' in the direction opposite to the arrow in FIG. As a result, the large gear 34 (34") and the small gear 35 (35') each rotate in the opposite direction to the arrow.
Pulley 37 configured as one piece with small gear 35 (35”)
(37') unwinds rope 8 (8').

Due to its own weight, the sluice l guide rail 11.11' (
(see Figure 4) and closes.

〔Effect of the invention〕

As described above, according to the present invention, without increasing the height of the spillway in the reservoir, the designed flood volume can be smoothly overflowed as planned, and the designed overflow depth can be utilized to the maximum. It is possible to store a larger amount of water than the previously described full water level storage amount corresponding to the height of the water outlet, that is, the maximum possible storage amount for the design plan overflow water depth. Therefore, the overflow water level originally planned will be maintained as it is, so even if you raise the previous full water level and store more water, the height of the reservoir spillway or the height of the embankment will be increased. In addition, the full water level can be adjusted and maintained at will without expanding the submerged area.

The inflowing floodwaters can also be drained out while automatically adjusting and closing the flood gates.

In addition, according to the present invention, problems such as stacking soil on conventionally installed spillways, rubber dams, tenter gates, siphons, etc. to increase the amount of water stored can be solved, and the water level is automatically adjusted according to the amount of water flowing into the reservoir. The sluice gates are opened and closed according to the water level in order to discharge the water while the water is flowing, so even if critical floodwaters flow in, the water level is automatically adjusted and the floodwaters are discharged, thereby safely protecting the dam itself and protecting the river bed. It prevents destruction, does not require manpower or power, is easier to construct than other facilities and methods, and is extremely inexpensive, so its effects are truly great.

Further, according to the present invention, it is possible to raise the water level of a weir in a river without constructing a fixed concrete system,
In addition to ensuring the height of the weir water level, if flood water exceeds the weir water level, the sluice gates are automatically opened and the amount of water corresponding to the inflow is discharged, so the water level of the river can be maintained at all times. The water level can be maintained at the weir level.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the principle when the method of the present invention is applied to a reservoir, Fig. 2 is an explanatory diagram showing the principle when the method is applied to a river, and Fig. 3 is a side view showing an embodiment of the device of the present invention. FIG. 4 is a perspective view of the same. Q... Spillwater discharge, R... Water guide platform, U... Riverbed, l... Sluice gate, 2... Float, 3... Drive means, D2... Changed full water level, D3 ...Design plan overflow water level, D4...Abnormal flood level, D6...Weir water level, D7...
・Design plan flood level. Patent applicant Shen Xiangduo

Claims (6)

[Claims] (1) A water gate is installed above the spillway of the reservoir, water is stored at a changed full water level higher than the spillway, a float is suspended at the changed full water level, and the water gate is adjusted in response to the rise and fall of the float. The water gate is opened and closed, and the operating ratio of the water gate relative to the rise and fall of the float as the water level fluctuates from the modified full water level to the design plan overflow water level is adjusted to the water depth from the modified full water level to the design plan overflow water level. An automatic water level adjustment method characterized in that the water level is set to a value corresponding to the sum of the water depth from the spillway to the design plan overflow water level and the water depth from the design plan overflow water level to the abnormal flood level. (2) A water gate is installed on the riverbed, a float is suspended at the weir water level of the river, and the water gate is opened and closed in response to the rise and fall of the float, and the water level from the weir water level to the design plan flood number is The operating ratio of the water gate with respect to the rise and fall of the float due to fluctuations is set to a value corresponding to the water depth from the weir water level to the design plan water level versus a value equivalent to the water depth from the riverbed to the design plan water level. automatic water level adjustment method. (3) A spillway is constructed by interlocking and connecting a sluice gate installed on the river bed so that it can move up and down, a float suspended at a changed full water level or weir water level due to the installation of the sluice gate, and the float and the sluice gate. An automatic water level adjustment device comprising a drive means for opening and closing the water gate in response to elevation. (4) The drive device sets the operating ratio of the flood gate for A precipitation of the float to a value corresponding to the water depth from the modified full water level to the design plan overflow water level to a value corresponding to the water depth from the spillway to the design plan overflow water level. The automatic water level adjustment device according to claim 3, further comprising an amplification mechanism that adjusts the water depth to a value corresponding to the sum of the water depth from the design plan overflow water level to the abnormal flood water level. (5) The driving device is an amplification mechanism that sets the operating ratio of the flood gate to the elevation of the float to a value corresponding to the water depth from the weir water level to the design plan water level to a value equivalent to the water depth from the riverbed to the design plan flood level. An automatic water level adjustment device according to claim (3), characterized in that it is equipped with: (6) The amplification mechanism is a gear mechanism consisting of a large gear that is operated in response to the elevation and descent of the float, and a small gear that meshes with the large gear and is integrally configured with a pulley connected by a water gate and a rope. An automatic water level adjustment device according to claim (4) or (5), characterized in that it is constructed by: