JP2012036619A - River water quality improvement system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a river water quality improvement system and a method capable of inexpensively improving water quality at a bottom part of a tidal river.SOLUTION: A water quality improvement system 10 to improve water quality of a tidal river 2 comprises: a water gate 12 which is constructed at an upstream side of the river 2 and vertically movable to open and close; a conduit 14 which communicates between the upstream side of the water gate 12 and a bottom part of a downstream side thereof and can open and close such communication; and control means 16 which controls the water gate 12 as well as the conduit 14 to close at high tide to raise a water level of the upstream side and controls the conduit 14 to open at low tide to channel water at the upstream side of the water gate 12 into the bottom part of the downstream side thereof.

Description

  The present invention relates to a river water quality improvement system and method.

  Conventionally, in a river close to the sea in an urban lowland such as the Nihonbashi River shown in FIG. 6, the flow of water flows backward or stays depending on the sea level fluctuation, so that the replacement of water is limited. As a result, near the river bottom, the dissolved oxygen concentration was low and the water quality was not suitable for living organisms, and sludge and the like were easily deposited. In the past, such problems have been dealt with by dredging the bottom of the river or by combining high-quality water from another river. All of them required a lot of labor and cost.

  As an existing technology for purifying the water quality of rivers and other areas close to the sea, there is a known method of purifying the water quality by installing a sluice at the entrance of the water area and guiding water into the water area using the difference in water level due to tides. (For example, refer to Patent Document 1). However, in the method of Patent Document 1, water mixing is unlikely to occur unless there is a density difference between the water guided from the water gate and the water at the bottom in the water area.

  In addition, a method for improving the water quality of a river by causing a flow in a river lower layer using a hinged sluice is known (for example, see Patent Document 2). However, in the case of tidal rivers, high-density salt water stays in the recesses at the bottom of the river, and with the tractive force only by opening the sluice gate, it flows so as to slide over the salt water in the recesses, and efficient water It is difficult to cause replacement.

JP 2006-274702 A JP 2008-274728 A

Nikken Sekkei, Inc., [online], [Search February 25, 2010], Internet <URL: http://www.nikken-civil.co.jp/developcase/contents/nihonbashigawa/nihonbashigawa.pdf > Takasaka et al., Water quality fluctuation characteristics in the Nihonbashi River tide area, Abstracts of the 35th Kanto Branch Technical Research Presentation, March 2008

  FIG. 7 is a longitudinal sectional view showing the water quality of the Nihonbashi River. FIG. 7A shows the distribution of salinity at low tide, and FIG. 7B shows the distribution of salinity at high tide. As shown in FIG. 7, it can be seen that there is an area where salt water is retained near the bottom of the river.

  FIG. 8 shows the distribution of the flow direction by depth during the rising tide period from low tide to high tide. The observation point is Joban Bridge. As shown in FIG. 8, it can be seen that there is a region that flows backward near the bottom of the river, and this is the cause of the retention of salt water.

  FIG. 9 is a longitudinal sectional view showing the water quality of the Nihonbashi River. FIGS. 9A to 9C show the distributions of dissolved oxygen concentration (DO), salinity and water temperature according to depth in the river longitudinal section, respectively. As shown in FIGS. 9 (a) and 9 (b), the salt water retention region present near the bottom of the river is a region where the dissolved oxygen concentration is low (the poor oxygen region illustrated by a circle in FIG. 9 (a)). It can be seen that water quality deteriorates in the tidal river affected by tidal fluctuations. Further, as shown in the water temperature distribution of FIG. 9C, the water temperature is low in the above region.

  In addition, as introduced in Non-Patent Document 1 above, sludge accumulates at the bottom of the river and peels off during the summer and emerges as scum on the water surface as shown in FIG. In addition, there is a problem that the river landscape is significantly deteriorated.

  For this reason, there has been a demand for the development of an inexpensive technique capable of preventing such deterioration of water quality in tidal rivers and accumulation of sludge at the bottom.

  This invention is made | formed in view of the above, Comprising: It aims at providing the cheap water quality improvement system and method of a river which can improve the water quality of the bottom part of a tidal river.

  In order to solve the above-mentioned problems and achieve the object, a river water quality improvement system according to claim 1 of the present invention is a water quality improvement system for improving the water quality of a tidal river, and is located upstream of the river. A sluice gate that can be opened and closed vertically, a water conduit that communicates with the upstream and downstream bottoms of the sluice, and that communication can be opened and closed, and the sluice and the water conduit are closed at high tide and the upstream of the sluice And a control means for guiding the water on the upstream side of the sluice to the bottom on the downstream side of the sluice by raising the water level on the side and opening the water channel at low tide.

  Further, the river water quality improvement system according to claim 2 of the present invention is characterized in that, in the above-described claim 1, the downstream side communication port is arranged upward.

  Moreover, the river water quality improvement system according to claim 3 of the present invention is characterized in that, in the above-described claim 1 or 2, the control means opens the sluice from the time of rising tide to the time of high tide. .

  A river water quality improvement system according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3 described above, the dissolved oxygen concentration at the bottom of the downstream side of the sluice is improved.

  A river water quality improvement system according to claim 5 of the present invention is characterized in that, in any one of claims 1 to 4 described above, a swirl vane is provided at a communication port on the downstream side of the water conduit. To do.

  A river water quality improvement system according to a sixth aspect of the present invention is the river water quality improvement system according to any one of the first to fourth aspects described above, wherein a porous tube is provided at a communication port on the downstream side of the water conduit. It is widely installed on the bottom of the river.

  A river water quality improvement method according to claim 7 of the present invention is a water quality improvement method for improving the water quality of a tidal river, wherein a sluice that can be opened and closed on the upstream side of the river, and an upstream of the sluice A water conduit that can open and close the communication, and the water gate and the water conduit are closed at high tide to raise the water level upstream of the sluice, and then at low tide The water guide channel is opened, and water on the upstream side of the sluice is introduced to the bottom on the downstream side of the sluice.

  According to the present invention, there is provided a water quality improvement system for improving the water quality of a tidal river, wherein a sluice gate provided on the upstream side of the river and which can be opened and closed is communicated with an upstream side and a downstream side bottom portion of the sluice gate. A waterway that can be opened and closed, and the water gate and the waterway are closed at high tide and the water level on the upstream side of the water gate is raised, and the waterway is opened at low tide and the upstream side of the water gate is opened. And a control means for guiding the water to the downstream bottom of the sluice, so that the upstream water is guided to the downstream bottom by the head difference formed between the upstream and downstream of the sluice, and this water flow and the river water at the bottom The water quality at the bottom of the tidal river can be improved at low cost by generating vertical mixing due to the difference in density and temperature and replacing the water remaining at the bottom.

FIG. 1 is a river longitudinal sectional view showing a state of the river water quality improvement system according to the present invention at the time of rising tide. FIG. 2 is a river longitudinal sectional view showing a state at the time of high tide of the river water quality improvement system according to the present invention. FIG. 3 is a river longitudinal sectional view showing a state of the river water quality improvement system according to the present invention at the time of low tide. FIG. 4 is a diagram illustrating an example of the structure of the downstream outlet of the water conduit. FIG. 5 is a diagram showing changes in the water level of the Nihonbashi River. FIG. 6 is a position diagram of the Nihonbashi River as an example of a river close to the sea. FIG. 7 is a longitudinal sectional view showing the water quality of the Nihonbashi River. FIG. 8 is a diagram showing the change over time in the flow direction of the Nihonbashi River. FIG. 9 is a longitudinal sectional view showing the water quality of the Nihonbashi River. FIG. 10 is a photograph showing the scum that has emerged on the surface of the river.

  Embodiments of a river water quality improvement system and method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  As shown in FIG. 1, a river water quality improvement system 10 according to the present invention is a water quality improvement system that improves the water quality of a tidal river 2, and is a cutoff plate that can be opened and closed up and down provided on the upstream side of the river 2. The sluice 12 comprising the sluice 12 is connected to the recess 4 at the upstream side and the downstream bottom of the sluice 12, and the conduit 14 (water conduit) capable of opening and closing the communication, and the open / close state of the sluice 12 and the conduit 14 are adjusted and controlled. And control means 16 for performing the above.

  As shown in FIG. 1, the control means 16 performs control to open the water gate 12 from the rising tide to the high tide.

  Then, as shown in FIG. 2, the sluice 12 and the conduit 14 are closed at high tide and water is stored upstream of the sluice 12 to raise the water level. When the sluice 12 and the conduit pipe 14 are maintained in the closed state from the time of low tide to the time of low tide, the river water level on the downstream side of the sluice 12 is lowered and a water level difference is generated on the upstream and downstream sides of the sluice 12. In this way, the water level on the upstream side of the sluice gate 12 is raised by the tide level fluctuation of the river water and stored as potential energy.

  Thereafter, as shown in FIG. 3, control is performed to open the water conduit 14 while keeping the sluice 12 closed at low tide. By this control, the water on the upstream side of the sluice 12 is guided to the recess 4 at the bottom on the downstream side of the sluice 12 by the head difference. Vertical mixing is generated at the water introduction point by the density difference and temperature difference between the water flow thus introduced and the river water in the recess 4. If it does so, the density difference of the water which retains in the recessed part 4 and upper river water will decrease, and replacement | exchange of water by river scavenging force will become easy. By doing so, water quality such as dissolved oxygen concentration at the bottom of the river can be improved.

  Thus, the opening and closing timing of the sluice 12 by the control means 16 is closed at high tide and open at low tide. In addition, it is suitable to make it an open state at the time of river increase. Further, the opening and closing timing of the water conduit 14 by the control means 16 is preferably opened after about 1 hour from high tide and closed at low tide. This is because the water level on the downstream side of the sluice 12 is sufficiently lowered after about 1 hour from high tide, and the water level difference from the upstream side of the sluice 12 becomes large so that the water quality can be improved efficiently.

  As shown in FIG. 4 (a), water is introduced into the river 2 from the water conduit 14 to the river 1 in a vertically upward direction, as shown in FIG. 4 (b). A method of discharging water downstream of the river with the downstream communication port 14a of the water pipe 14 directed obliquely upward, as shown in FIG. 4C, a porous tube 18 is provided at the downstream communication port 14a of the water conduit 14, A method in which the pipe 18 is widely installed on the bottom of the river and water is introduced on the surface, as shown in FIG. 4 (d), a method in which the swirl vane 20 is provided in the downstream communication port 14a of the water guide pipe 14 and the water is stirred and guided. Can be used.

  In addition, the position of the upstream communication port of the water conduit 14 needs to be a position where the water quality is relatively better than that of the recess 4 on the downstream side. As the position of the upstream communication port, for example, a river bottom convex part or a position relatively higher than the river bottom (a position higher than the maximum convex part of a certain range of river bottom irregularities) or a position such as an upper layer to a middle layer of a river It is possible.

  Fig. 5 is a diagram showing an example of the water level change at the Joban Bridge in the Nihonbashi River (Non-Patent Document 2, "Takasaka et al., Water Quality Fluctuation Characteristics in the Nihonbashi River Tide Area, 35th Kanto Branch Technical Research Presentation (See Abstract, March 2008).

  As shown in Fig. 5 and Fig. 6, the observation point Joban Bridge is 2km upstream from the estuary, but the influence of the tide level change is remarkable, and in Fig. 5 the tide level change is about 1.5m, About 2m of tide level change was observed during this period. In Japan, the coasts, ports, and canals that face the sea directly have a maximum tidal level change of about 4.5m at the time of the tide and about 0.1m at the time of the tide.

  Therefore, it is possible to improve the water quality near the bottom of the river at low cost by using renewable energy due to such tide level fluctuations. That is, the water level difference is formed on the upstream and downstream sides of the sluice 12 by using the water level rise at the time of high tide to store water upstream of the sluice 12 while using the water level decrease at the time of low tide. Then, the water on the upstream side of the sluice 12 is guided to the bottom on the downstream side by this water head difference, and vertical mixing is caused at the water introduction point by this water flow, density difference and temperature difference. By doing so, the water quality near the bottom of the river can be improved at low cost.

  As described above, according to the present invention, there is provided a water quality improvement system for improving the water quality of a tidal river, the sluice gate provided on the upstream side of the river that can be opened and closed, and the upstream side and the downstream side of the sluice gate. A water conduit that communicates with the bottom of the side and that can be opened and closed; and the water gate and the water conduit are closed at high tide and the water level upstream of the water gate is raised, and the water conduit is opened at low tide Control means for guiding the water upstream of the sluice to the bottom of the downstream of the sluice, so that the water on the upstream side is led to the bottom of the downstream by the head difference formed between the upstream and downstream of the sluice. The water quality at the bottom of the tidal river can be improved at low cost by generating vertical mixing due to the density difference and temperature difference between the river and the river water at the bottom and replacing the water staying at the bottom.

  As described above, the river water quality improvement system and method according to the present invention are useful for improving the water quality at the bottom of tidal rivers, and are particularly suitable for improving the water quality of the recesses near the bottom where salt water tends to stay.

2 River 4 Concave 10 River water quality improvement system 12 Sluice 14 Conduit (conduct)
16 Control means 18 Porous tube 20 Swivel blade

Claims (7)

A water quality improvement system that improves the quality of tidal rivers,
A sluice gate that can be opened and closed vertically on the upstream side of the river;
A water conduit that communicates the upstream side and the downstream bottom of the sluice, and that can be opened and closed;
After the sluice and the conduit are closed at high tide and the water level upstream of the sluice is raised, the conduit is opened at low tide and water upstream of the sluice is guided to the bottom downstream of the sluice And a water quality improvement system for a river.   The river water quality improvement system according to claim 1, wherein a communication port on the downstream side of the water conduit is arranged upward.   The river water quality improvement system according to claim 1 or 2, wherein the control means opens the sluice from a rising tide to a high tide.   The river water quality improvement system according to any one of claims 1 to 3, wherein the dissolved oxygen concentration at the bottom of the downstream side of the sluice is improved.   The river water quality improvement system according to any one of claims 1 to 4, wherein swirl vanes are provided at a communication port on the downstream side of the water conduit.   The river water quality improvement system according to any one of claims 1 to 4, wherein a porous pipe is provided at a communication port on the downstream side of the water conduit, and the porous pipe is widely installed on a river bottom. A water quality improvement method for improving the water quality of tidal rivers,
A sluice that can be opened and closed on the upstream side of the river;
The upstream side and downstream side bottom of the sluice gate are communicated, and a water conduit that can open and close the communication is provided,
After the sluice and the conduit are closed at high tide and the water level upstream of the sluice is raised, the conduit is opened at low tide and water upstream of the sluice is guided to the bottom downstream of the sluice River water quality improvement method characterized by doing.