JP2596413B2 - Larvae induction method and river structure for it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for guiding a larva, which has just hatched from an egg, to flow down a predetermined path of a river, and a river structure therefor.

[0002]

2. Description of the Related Art Ayu is a valuable fish from the fishing industry and fishing grounds, and is a representative fish in Japan. Ayu has the habit of laying eggs in the middle and lower reaches of rivers and hatching from eggs. It is growing.

[0003] However, if there is an intake port for water or the like in the middle of the river, the baby ayu having weak swimming power is taken into the intake port by the flow of the river and cannot go to the sea.
Therefore, if the river where the sweetfish lives is provided with an intake, it is necessary to take measures to prevent the sweetfish from being taken into the intake. As a countermeasure to prevent fish in the river from being taken into the intake, if the fish have a relatively large swimming ability, move the fish near the intake to the opposite side by taking measures against straying such as an electric screen. Is effective, but this method cannot be applied to larvae with weak swimming power, and no effective measures have been taken to prevent larvae from being taken into the water intake.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and allows a larva having a weak swimming power, such as larvae, to flow down along a predetermined route of a river. It is an object of the present invention to provide an effective method for guiding the water to be introduced, specifically, an effective method for guiding the water to the opposite shore near the intake so as not to be taken into the intake, and a river structure therefor.

[0005]

According to a first aspect of the present invention, there is provided a method for inducing a larva in a river, the method including the step of causing the center of the river to follow a route in which the larva is to be induced. A method for inducing larvae is provided. According to a second aspect of the present invention, in the method for inducing larvae in a river having an intake on one shore side, the flow center from the upstream side at least a predetermined distance from the intake position of the river to at least the position immediately before the intake port is determined. And a method for inducing a larva, which is set on the other shore side from the center in the width direction of the river.

According to a third aspect of the present invention, in a river structure having an intake port on one shore side, the intake port is located at a predetermined distance from the intake port position of the river and at least a position immediately before the intake port. Provided is a river structure characterized in that the riverbed on the other shore is formed deeper than the riverbed on the shore.
The invention according to claim 4 is, in a river structure having an intake port on one shore side, from a shore where the intake port is located to the opposite shore at least a predetermined distance from the intake port of the river to a position immediately in front of the intake port. Provide a river structure characterized by the installation of a headwater dike.

Here, the larva means a fish that has just hatched from an egg. When the larva becomes larger, it becomes a fry, and when it becomes larger, it becomes an adult (parent). As a representative of such larvae, there is larva, which is about 5 mm in length, has weak swimming power, and swims at a maximum speed of about 3 cm / s.
The average swimming speed for a long time is estimated to be about 1 cm / s. In addition, the present invention is applicable to various larvae having a weak swimming ability other than larvae.

[0008] The center of the river is the center of the flow of the river, and means the position where the flow velocity is the fastest in the width direction of the river. Then, in a long straight section of the river, when the depth of the river bottom is almost equal in the width direction, or when the center side in the width direction is the deepest and almost right and left symmetric, the center of the river substantially coincides with the center of the river in the width direction. . In addition, the predetermined distance (that is, how far the control start point of the flow center should be on the upstream side from the water inlet).
Is appropriately determined according to the flow velocity and the river width of the river and the opening width of the intake port.

[0009]

The present inventors have studied the flow of larvae, which are representative of larvae with weak swimming ability, in rivers, and found the following. 7 to 10 show the results of examining the distribution on the river cross section of the sweetfish flowing down the river and the distribution of the flow velocity of the river at the same point in the same river cross section. Here, the cross section of the river is divided into nine layers, which are divided into the surface layer, middle layer, and lower layer in the depth direction, and left, middle, and right in the width direction. ing.

[0010] Figure 7 November one day of仔鮎many flows down, by measuring the falling quantity of Nagareseki 1 m ² · daily仔鮎shows the ratio of falling weight in river cross each position FIG. 8 is a distribution diagram showing the average value (m / sec) of the flow velocity of the river measured on the same day for 24 hours at each position of the river cross section. FIG. 9 is a distribution diagram showing a flow rate ratio for a result of performing the same measurement on another day in November, and FIG. 10 is a distribution diagram showing an average flow velocity measured on the same day. is there.

As can be seen from these figures, the center of the river is located substantially at the center of the river in the width direction, and most of the sweetfish flows down the center of the river, which is the center of the river, in the width direction. In other words, it is thought that larvae are active at night because they are likely to die because they cannot withstand the ultraviolet rays in the daytime,
In order to flow down the river in a short time from the time when almost no UV light was emitted in the evening until before sunrise the next morning, it was found to flow down the river along the fast-flowing core.

The flow velocity at the middle position of each layer is about twice the flow velocity at the left and right positions, whereas the flow rate at the middle position of each layer is 88% of the whole layer.
It was found that most of the sweetfish could be allowed to flow down the flow center with a flow velocity difference of about twice. Therefore, according to the method of claim 1, the larva flows down the guiding path of the river along the flow center.

According to the method of the present invention, the larvae are located at the intake of the river, compared with the case where the flow center near the intake is located at the center in the width direction and at one of the shores. It is easy to flow along the distant water core, and it is difficult to flow into the water intake. According to the structure of the river according to claim 3, the flow center near the intake of this river is not at the center in the width direction but at the other shore side where the river bottom is deep, so that the flow center is at the center in the width direction and one shore therefrom. In comparison with the river on the side, the larvae in this river are more likely to flow along the core far from the intake at the intake, and harder to flow into the intake.

According to the structure of the river according to claim 4, since the flow center near the intake of this river is not at the center in the width direction but on the other shore side due to the installation of the dike, the flow center is located at the center in the width direction. Compared to a river on one shore side, larvae in this river are more likely to flow along the core far from the intake at the intake, and are less likely to flow into the intake.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a first embodiment of a river to which the present invention is applied. On the right bank of this river 1 where the baby ayu flows down,
There is an intake 12 for the water 11. The depth of the river bottom of the river 1 is at least in the entire portion shown in FIG. 1, since the center in the width direction is the deepest and is almost symmetrical, so that the center C of the river 1 in FIG. Direction center C ₀
Matches. Further, in the river 1, intake Until A ₂ points downstream of the water intake port 12 from the upstream side of the A ₁ point from 12, Nagarekokoro C and the right bank distance in the width direction of the L ₁ is the water inlet 12
To be larger than the opening width L ₂ of, it is widening the river than other portions.

[0016] Therefore, the porridge in this river 1 is
It flows down along the intake port 12 and passes through a position far from the right bank near the intake port 12, so it is difficult to flow into the intake port 12. Note that the distance L
Endpoint intake of a section larger than the opening width L _{2 1} 12
Of is also a last minute obtained the effect, in the river 1, because you are the section to the _two points A on the downstream side of the intake 12, the effect is particularly large.

[0017] Figure 2 is a plan view showing a second embodiment of the rivers to which the present invention is applied, FIG. 3 is a X ₁ -X ₁ line sectional view of FIG. 2, FIG. 4 is X ₂ in FIG. 2 it is -X ₂ sectional view taken along line. This river 2 also has an intake 22 for irrigation water 21 on the right bank,
From the upstream side of the B ₁ point from the water intake 22 to the downstream side of the B ₂ points intake 22, a riverbed 2L of the left bank side of right bank riverbed 2R
Yes and deeper formation, depth of the downstream side of the river bottom of the upstream and B ₂ points from _one point B is nearly symmetrical with the most deeply widthwise center. In addition, the river bottom 2L on the left bank side is B ₁
From the point to the intake 22 position, it gradually becomes deeper and becomes the deepest at the intake 21 position, from which B ₂
It gradually becomes shallower toward the point.

As a result, the center C _{1 of the} river 2 becomes B
There widthwise center C ₀ is upstream of the _point, is toward the downstream from _a point B approaches the most left bank at intake 22 positioned to move gradually on the left bank side, it is further toward the downstream therefrom gradually to coincide with the widthwise center C widthwise center C ₀ at _two points B approaches _0, in the widthwise center C ₀ is downstream from it. Therefore, this仔鮎in rivers 2 flows down along the Nagarekokoro C _1, in the vicinity of intake port 22 through the position far from the right bank,
It is difficult to flow into the intake 22. Although also a just before the end point of the interval of the intake port 22 of the left bank side Nagarekokoro C ₁ than the width-direction center C ₀ The effect can be obtained, in the river 2, downstream from the water introducing opening 22 of the section due to the up _two points B, the effect is particularly large.

FIG. 5 is a plan view showing a third embodiment of a river to which the present invention is applied, and FIG. 6 is a sectional view taken along line YY of FIG. This river 3 also has a water intake 32 on the right bank toward the irrigation water 31.
Intake 32 from the presence, upstream of the D ₁ point than water intake 32
The up downstream of the D ₂ points, the riverbed 3L of left bank Yes and deeper than riverbed 3R of the right bank side, upstream of the _point D and D
The depth of the riverbed downstream from the _two points is almost symmetrical with the center in the width direction being the deepest. In addition, 3L of river bottom on the left bank side
It is deepest becomes the intake port 32 located gradually deeper toward the intake port 32 located from _a point D, and gradually shallower toward Here _two points D.

[0020] In addition, this river 3, slightly until the upstream side, the flow of water system Engineering 4a~4e towards the left bank from the right bank of the river water intake 32 from further upstream side than the _point D It is installed almost at right angles to. Each diversion 4a-4
e is installed at predetermined intervals in the direction of flow, and the length of protrusion from the right bank is increased from the upstream side to the downstream side, and about 1/4 of the river width at the most upstream dike 4a. However, the most downstream dike 4e protrudes to about half the river width.

Thus, the center C _{2 of the} river 3 becomes D
There widthwise center C ₀ is upstream of the _point, the direction from _a point D on the downstream approach the most left bank at intake 32 positioned to move gradually on the left bank side, is further toward the downstream therefrom gradually to coincide with the widthwise center C widthwise center C ₀ at _two points D approaches _0, in the widthwise center C ₀ is downstream from it. Furthermore, within this river 3, along a position where the slightly right bank side of the widthwise center C _0, the downstream end of the intake port 32 from the position of around the most downstream water system Engineering 4e is installed A partition 5 that is continuous to the position is provided. The partition wall 5 is composed of a riverbed 3L on the left bank and a riverbed 3R on the right bank which are different in depth.
It is installed by embedding the lower part at the boundary position with.

Therefore, the larvae in this river 3 are
It flows down along ₂ and passes near the intake 32 far from the right bank, so it is difficult to flow into the intake 32. Note that the same effect can be obtained even if the end point of the section where the flow center C ₂ is located on the left bank side from the center C ₀ in the width direction is immediately before the intake port 32, but in the river 3, the section is located downstream from the intake port 32. because of being up to ₂ points D, the effect is particularly large.

In the river 3, since the partition wall 5 is located at a position facing the intake port 32, the sweetfish flowing down along the flow center C ₂ immediately before the intake port 32 is opposed to the intake port 32. Since it can be effectively prevented from going to the right bank side at this position, the number of sweetfish flowing into the water intake 32 can be significantly reduced.

[0024]

As described above, according to the method of the first aspect, the larvae in the river can flow down along the predetermined guiding route. According to the method of claim 2, in a river having an intake on one shore side, the flow center in the vicinity of the intake is located at the center in the width direction and on the other shore side than in the river. It is possible to make it difficult for the larva to flow into the water inlet.

According to the structure of the river according to claims 3 and 4,
According to the method of claim 2, in a river having an intake on one shore side, the flow center near the intake port is located at the center in the width direction and on the other shore side than in the river. It is possible to make it difficult for the larva to flow into the water inlet.

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment of a river to which the present invention is applied.

FIG. 2 is a plan view showing a second embodiment of a river to which the present invention is applied.

FIG. 3 is a sectional view taken along line X ₁ -X ₁ of FIG. 2;

FIG. 4 is a sectional view taken along line X ₂ -X _{2 in} FIG. 2;

FIG. 5 is a plan view showing a third embodiment of a river to which the present invention is applied.

FIG. 6 is a sectional view taken along line YY of FIG. 2;

FIG. 7 is a distribution diagram showing an example of the ratio of the amount of the flow of larvae at each position of a river cross section.

FIG. 8 shows an example of a flow velocity distribution at each position of a river section (FIG. 7)
FIG. 9 is a distribution diagram showing the results measured on the same day.

FIG. 9 is a distribution diagram showing an example of the ratio of the amount of the flow of a baby sweetfish at each position of a river cross section.

FIG. 10 is a distribution diagram showing an example of flow velocity distribution (measured on the same day as FIG. 9) at each position of a river cross section.

[Explanation of symbols]

Reference Signs List 1 river 2 river 3 river 4a diversion 4b diversion 4c diversion 4d diversion 4e diversion 12 intake 22 intake 32 intake C flow center C ₀ center of river width C ₁ flow center C ₂ Nagarekokoro C ₃ Nagarekokoro 2L left bank (the other shore) side of the river bottom 2R right bank (there are intake shore) side of the riverbed 3L left bank of (other shore) side riverbed 3R right bank (there are intake shore) side Riverbed

Claims (4)

(57) [Claims] 1. A method for inducing larvae in a river, the method comprising inducing a larva to be guided along a flow center of the river. 2. A method for inducing larvae in a river having an intake on one shore side, wherein a flow center from a position upstream of the intake position of the river by at least a predetermined distance to at least a position immediately before the intake port is determined. A method for inducing larvae, characterized in that the larva is set on the other shore side from the center in the width direction of the river. 3. In a river structure having an intake on one shore side, a predetermined distance from the intake position of the river to at least a position immediately in front of the intake from the river bottom on the shore side where the intake is located. A river structure characterized by the deep formation of the riverbed on the other shore side. 4. In a river structure having an intake on one shore side, water flowing from the shore where the intake is located to the opposite shore from a predetermined distance upstream from the intake of the river to at least a position immediately before the intake. A river structure characterized by the construction of a work.