JP4247285B2 - Method for regenerating submerged plant community and method for purifying water - Google Patents

Method for regenerating submerged plant community and method for purifying water Download PDF

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JP4247285B2
JP4247285B2 JP2007102571A JP2007102571A JP4247285B2 JP 4247285 B2 JP4247285 B2 JP 4247285B2 JP 2007102571 A JP2007102571 A JP 2007102571A JP 2007102571 A JP2007102571 A JP 2007102571A JP 4247285 B2 JP4247285 B2 JP 4247285B2
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昭太 袋
義彦 島多
洋 久保田
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本発明は、沈水植物群落、典型的には湖沼、池等の閉鎖性水域の沈水植物群落を再生する方法及びこの沈水植物群落利用した水質浄化技術に関する。   The present invention relates to a method for regenerating a submerged plant community, typically a submerged plant community in a closed water area such as a lake or a pond, and a water purification technology using the submerged plant community.

湖沼や池等の閉鎖性水域の水質汚濁対策として、湖沼水質保全特別措置法(以下、湖沼法)が1984年に公布されて以後、工場及び事業場の排水や、生活排水の負荷量規制など、特定汚染源対策がこれまでに実施されてきたが、それにも拘らず、指定湖沼等の閉鎖性水域の水質には、顕著な改善が殆どみられないのが現状である。これに対し、平成17年6月に湖沼法が改正され、面源負荷削減のための流出水対策地区や、自然浄化機能の活用を推進するための湖辺環境(湖辺植物)の保護地区の指定が新たに追加されるなど、閉鎖性水域の水質改善のための湖辺植生帯の保全・再生事業は、今後ますます拡大してくるものと予想される。   As measures against water pollution in closed water areas such as lakes and ponds, the Lake Water Quality Conservation Special Measures Law (hereinafter referred to as the Lake Law) was promulgated in 1984, and so on. Despite the fact that specific pollution source countermeasures have been implemented so far, in spite of this, there is almost no noticeable improvement in the water quality of closed waters such as designated lakes. On the other hand, the Lake Law was revised in June 2005, and the runoff water countermeasure area for reducing the surface load and the lakeside environment (lakeside plant) protection area for promoting the use of the natural purification function The lakeside vegetation zone conservation and restoration project for the improvement of water quality in closed water areas is expected to expand further in the future.

このような閉鎖性水域の水質改善に、近年、沈水植物群落を利用することが試みられている。詳しくは、湖辺植生帯は、葦(ヨシ)などの抽水植物帯や、ヒシなどの浮葉植物帯や、クロモなどの沈水植物帯からなり、このうち沈水植物は、水面下に根・茎・葉のすべてが存在する植物であり、水質汚濁の原因となるアオコ等の発生を助長する窒素や燐などの栄養塩の取り込み機能や、アオコを捕食する水質浄化作用の高いミジンコなどの動物プランクトンを魚から保護する隠れ家構造となることで、これらの動物プランクトンの増殖を促す機能や、植物プランクトン等の懸濁物質の沈降促進機能などを有するため、水質浄化機能が大きい。そして他の植生帯が、湖沼等において水際の線を形成するのに対し、沈水植物は4m程度の水深まで生育できることから、沈水植物群落による広大な面を形成することができるなど、水質に与える量的な効果が大きい。しかも、沈水植物の群落は、上述の水質浄化機能だけでなく、水鳥の餌としての機能、魚類の産卵礁機能、稚魚や底生動物の棲み家機能など、生態系回復作用といった質的な効果も大きい。   In recent years, attempts have been made to use submerged plant communities to improve water quality in such closed waters. Specifically, the lakeside vegetation zone is composed of water-extracted plant zones such as reeds, floating leaf plant zones such as eagles, and submerged plant zones such as chromo, among which submerged plants are roots, stems, It is a plant where all leaves exist, and it has a function of uptake of nutrients such as nitrogen and phosphorus that promotes the occurrence of blue water, which causes water pollution, and a zooplankton such as Daphnia, which has a high water purification effect to prey on blue water. Since it has a hideout structure that protects from fish, it has a function of promoting the growth of these zooplanktons and a function of promoting sedimentation of suspended substances such as phytoplanktons, and thus has a large water purification function. And while other vegetation zones form a line at the edge of lakes and marshes, submerged plants can grow to a depth of about 4 m, so they can form a vast surface due to submerged plant communities, giving water quality. Great quantitative effect. Moreover, the submerged plant community is not only a water purification function as described above, but also a qualitative effect such as a waterfowl feed function, a spawning reef function for fishes, and a habitat function for fry and benthic animals. Is also big.

このように、沈水植物は湖沼等の水質、生態系に対してその量及び質的な効果が他の植生帯より優れているため、沈水植物群落を再生することによって、閉鎖性水域の水環境の回復を加速化することが期待できる。   In this way, submerged plants are superior to other vegetation zones in terms of water quality and ecosystems such as lakes and marshes, so by regenerating submerged plant communities, Can be expected to accelerate recovery.

しかしながら沈水植物は、わが国における高度経済成長期前後の時期に、湖沼等の閉鎖性水域で栄養塩が大量に流れ込んで負荷が増大し、アオコ等植物プランクトンが大量に発生して水域の透明度が急激に低下したことにより、植物の生育に必要不可欠な光条件が悪化したことや、農地で過剰に散布された除草剤などの農薬が湖沼、池沼等の閉鎖性水域へ流入するなどの影響によって、沈水植物は、その大部分が消失または衰退し、現在に至っては絶滅危惧種となっている植物種も少なくない。特に中小規模の湖沼、池沼では沈水植物が完全に消失してしまった水域が殆どである。   However, in submerged plants around Japan during the period of high economic growth, a large amount of nutrients flow in closed waters such as lakes and marshes, and the load increases. As a result, the light conditions indispensable for plant growth have deteriorated, and pesticides such as herbicides overspread on farmland flow into closed waters such as lakes and ponds. Most submerged plants have disappeared or declined, and many plant species are endangered to date. Especially in small and medium-sized lakes and ponds, most of the water areas have lost their submerged plants.

これまで、工場及び事業場からの排水や生活排水の負荷量規制や農薬規制等がなされてきたため、現状では沈水植物群落を再生するための主要な制限因子は水中の光環境であり、一部波浪も制限因子であることがわかっている。光環境によって沈水植物群落の再生が制限されるのは、上述のように、アオコ等植物プランクトンが大量に発生していると、水底の植物の成長に必要な太陽光が水底に届かないからであり、波浪により再生が制限されるのは、大規模な湖沼等の中には波浪の影響が大きく、沈水植物が水底に根をしっかりと張る前に巻き上げられてしまうからである。   Until now, the regulation of the amount of wastewater discharged from factories and workplaces and the amount of domestic wastewater and the control of agricultural chemicals have been made, so at present the main limiting factor for regenerating submerged plant communities is the underwater light environment. Waves are also known to be a limiting factor. As described above, the regeneration of submerged plant communities is limited by the light environment, because, if a large amount of phytoplankton, such as blue sea bream, is generated, the sunlight necessary for the growth of plants on the bottom does not reach the bottom. There is a reason why waves are limited to regeneration because large waves and lakes are affected by waves, and the submerged plants are rolled up before they firmly root their roots.

従来、沈水植物群落の再生手法としては、水底の底泥中に眠る在来種の植物の種子や殖芽などの土壌シードバンクを水底に撒き出す方法が実施されてきたが、上述のように、水中の光環境が劣悪なため、浅い場所には在来種がいったん再生するが、そのような浅い水深は葦などの抽水植物や浮葉植物なども成長できるため最終的には光の競合に負け、再消失してしまう。したがってこのような方法では、沈水植物群落の再生は困難である。   Conventionally, as a method for regenerating submerged plant communities, a method has been implemented in which soil seed banks such as seeds and buds of native species that sleep in the bottom mud of the bottom of the water are sprinkled onto the bottom of the water. However, because the light environment in the water is poor, native species regenerate once in shallow places, but such shallow water depths can also grow drought plants such as coral and floating leaf plants, so ultimately they will compete for light. Loss and disappears again. Therefore, it is difficult to regenerate submerged plant communities by such a method.

これに対し、近年は、沈水植物の供給と経済的な光環境の改善技術を組み合わせた方法、例えばバイオマニピュレーションによる方法や、水位制御による方法や、植生浮島による方法が開発されてきた。このうち、バイオマニピュレーションは、光環境を悪化させているアオコ等植物プランクトンを捕食するミジンコなどの動物プランクトンを捕食する魚類を除去するなどの生態系の操作により透明度を改善する方法であり、これに土壌シードバンクの撒き出しや苗株の移植などの方法を組み合わせて沈水植物群落を再生する。また、水位制御による方法は、沈水植物群落の再生初期は湖沼等の水位を例えば30cm程度に下げることによって、沈水植物の成長に十分な太陽光を水底に供給し、植物の成長と共にその水位を上昇させることで沈水植物群落を再生する方法である。また、植生浮島による方法は、下記の特許文献に開示されているように、抽水植物を植栽した植生浮島と沈水植物を植栽した植生浮島を水面に浮かべ、抽水植物の浮島で透明度を改善し、沈水植物の植生浮島で植物を栽培し、透明度の改善と共にその栽培水深を徐々に増加していき、最終的に水域の水底に沈水植物群落を再生する方法である。
特開2007−29058号公報
On the other hand, in recent years, methods that combine the supply of submerged plants and economic light environment improvement techniques, such as a method using biomanipulation, a method using water level control, and a method using vegetation floating islands have been developed. Biomanipulation is a method of improving transparency by manipulating ecosystems such as removing fish that prey on zooplankton, such as daphnia, that prey on phytoplankton, such as sea lions, which are deteriorating the light environment. Regenerate submerged plant communities by combining methods such as seeding of soil seed banks and transplanting of seedlings. In addition, the water level control method supplies sunlight sufficient for the growth of submerged plants to the bottom of the water by reducing the water level of lakes and marshes, for example, to about 30 cm at the initial stage of regeneration of submerged plant communities. It is a method of regenerating a submerged plant community by raising it. In addition, as disclosed in the following patent document, the method using vegetation floating islands floats vegetation floating islands planted with water-extracted plants and vegetation floating islands planted with submerged plants on the surface of the water, and improves transparency on the floating islands of water-extracted plants. This is a method of cultivating a plant on floating vegetation floating islands, gradually increasing the cultivation water depth with improvement in transparency, and finally regenerating a submerged plant community on the bottom of the water area.
JP 2007-29058 A

しかしながら、バイオマニピュレーションによる方法は、湖沼等の水域の特性によってその生態系が異なるため、透明度の改善が図れない場合の事例も数多くあり、また魚類の除去などは漁業等利水制限に左右され、大規模湖沼では魚類の大部分の除去は非常に困難であり、しかも生態系への悪影響を及ぼすおそれがあるといった問題が指摘される。また、波浪の影響がある湖沼では適さない。   However, biomanipulation methods differ in ecosystems depending on the characteristics of water bodies such as lakes and marshes, so there are many cases where transparency cannot be improved, and removal of fish depends on water use restrictions such as fisheries. In large-scale lakes, it is very difficult to remove the majority of fish, and there is a problem that it may adversely affect the ecosystem. In addition, it is not suitable for lakes and marshes affected by waves.

また、水位制御による方法は、漁業及び農業など利水上の制約条件がある湖沼では採用が困難であり、大規模湖沼での水位制御は困難であり、さらに、波浪の影響がある湖沼では適さない。   In addition, the water level control method is difficult to adopt in lakes and lakes that have water-use constraints such as fishing and agriculture, and is difficult to control in large-scale lakes. .

また、植生浮島による方法は、利水制限にはほとんど左右されず、波浪についてもある程度の消波効果があり、経済的に安価で有効な方法ではあるが、大規模湖沼を対象とする際には、植生浮島の設置数量が増大するため、費用が高くなるおそれがある。   In addition, the method using vegetation floating islands is hardly affected by water use restrictions, and there is a certain amount of wave-dissipating effect on waves, and it is an economically cheap and effective method, but when targeting large-scale lakes. Because of the increased number of vegetation floating islands installed, the cost may increase.

本発明は、上述のような問題に鑑みてなされたもので、その技術的課題は、生態系への悪影響を殆ど与えずに、大規模湖沼でも容易かつ低コストで沈水植物群落の再生を行い、ひいては、これによって閉鎖性水域の水質浄化を図ることにある。   The present invention has been made in view of the above-mentioned problems, and its technical problem is to regenerate submerged plant communities easily and at low cost even in large-scale lakes with little adverse effect on the ecosystem. Therefore, this is to purify the water quality of the closed water area.

上述の技術的課題を有効に解決するための手段として、請求項1の発明に係る沈水植物群落を再生する方法は、水域内に、この水域の一部を他部から隔離する囲いを設けて、この隔離された水域の透明度を改善してから、前記隔離された水域の中で沈水植物を生育させ、前記沈水植物の群落が前記隔離された水域における所定の面積まで成長したら、前記囲いによって隔離する水域の面積を適宜拡大して引き続き前記沈水植物を生育させるといった工程を繰り返すものである。この方法によれば、水域に、その一部を他部から隔離する囲いを設けて沈水植物を栽培することで、アオコなどの植物プランクトンが発生した周りの汚濁水又はアオコなどの植物プランクトンが発生しやすい周りの汚濁水の流入を防ぎ、波浪を遮ることができるため、囲い内で確実に沈水植物を成長させて群落を形成し、その繁茂領域を囲いによって漸次拡大させていくことができる。 As a means for effectively solving the technical problem described above, the method for regenerating a submerged plant community according to the invention of claim 1 is provided with an enclosure for isolating a part of the water area from other parts in the water area. After improving the transparency of the isolated water area, grow a submerged plant in the isolated water area, and when the submerged plant community has grown to a predetermined area in the isolated water area, the enclosure The process of expanding the area of the water area to be isolated as appropriate and subsequently growing the submerged plant is repeated. According to this method, by enclosing a part of the water area with an enclosure that isolates a part from other parts, cultivating a submerged plant, polluted water around which the phytoplankton such as the sea bream was generated or phytoplankton such as the sea bream is generated. Since it is possible to prevent the inflow of polluted water around the water, and to block the waves, it is possible to reliably grow submerged plants in the enclosure to form a community, and to gradually expand the prosperous area by the enclosure.

また、請求項2の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、水面から50cm以深を囲うものである。   The method for regenerating a submerged plant community according to the invention of claim 2 is the method of claim 1, wherein the enclosure surrounds a depth of 50 cm or more from the water surface.

また、請求項3の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、水面から水底までを囲うものである。   The method for regenerating a submerged plant community according to claim 3 is the method according to claim 1, wherein the enclosure surrounds the water surface to the bottom of the water.

また、請求項4の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、粒径が2μm以上の粒子を通さない材質からなるものである。このような材質のものを用いれば、アオコなどの植物プランクトンが殆ど通過できなくなる。   The method for regenerating a submerged plant community according to the invention of claim 4 is the method of claim 1, wherein the enclosure is made of a material that does not pass particles having a particle size of 2 μm or more. If a material of such a material is used, phytoplankton such as a giant sea bream can hardly pass.

また、請求項5の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、遮水性を有する材質からなるものである。このような材質のものを用いれば、例えば窒素やリンが非常に高濃度で含まれアオコが発生しやすい汚濁水や、洗剤、農薬など、沈水植物の生育に悪影響を与える物質が溶解している汚濁水が囲い内へ侵入するのを、有効に遮断できる。   According to a fifth aspect of the present invention, there is provided a method for regenerating a submerged plant community, wherein the enclosure is made of a material having a water shielding property. Using such materials dissolves substances that adversely affect the growth of submerged plants, such as polluted water that contains nitrogen and phosphorus in very high concentrations and is prone to the occurrence of watermelon, detergents, and agricultural chemicals. It can effectively block contaminated water from entering the enclosure.

また、請求項6の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、囲い本体と、この囲い本体の上部を水面もしくは水面上に支持するためのフロートと、前記囲い本体の下部を水底に繋着するシートアンカーと、前記フロートを水底に繋着するフロートアンカーとからなるものである。   A method for regenerating a submerged plant community according to claim 6 is the method according to claim 1, wherein the enclosure is a float for supporting the enclosure body and the upper part of the enclosure body on the water surface or the water surface. And a seat anchor for connecting the lower part of the enclosure main body to the bottom of the water and a float anchor for connecting the float to the bottom of the water.

また、請求項7の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いが、囲い本体と、この囲い本体を固定する支持枠と、前記囲い本体の下部を水底に固定するシートアンカーとからなるものである。   A method for regenerating a submerged plant community according to claim 7 is the method according to claim 1, wherein the enclosure includes an enclosure main body, a support frame for fixing the enclosure main body, and a lower portion of the enclosure main body. It consists of a seat anchor fixed to the bottom of the water.

また、請求項8の発明に係る沈水植物群落を再生する方法は、請求項1に記載の方法において、囲いの拡大は、この囲いによって隔離される水域の面積に対して、前記囲い内の沈水植物群落の占有面積が10〜40%が確保されるようにするものである。   Further, the method for regenerating a submerged plant community according to the invention of claim 8 is the method of claim 1, wherein the enlargement of the enclosure is caused by the subsidence in the enclosure relative to the area of the water area isolated by the enclosure. The occupation area of the plant community is ensured 10 to 40%.

また、請求項9の発明に係る水質浄化方法は、請求項1〜8のうちいずれかの方法により再生される沈水植物群落によって閉鎖性水域の水質を浄化するものである。   Moreover, the water quality purification method according to the invention of claim 9 purifies the water quality of the closed water area by the submerged plant community regenerated by any one of claims 1-8.

本発明によれば、波浪の影響の大きい水域や、大規模湖沼でも容易に沈水植物の群落を再生することができ、しかも、大型のプラント等の物理化学的な装置や、薬剤を必要としないため、湖沼等閉鎖性水域の生態系に悪影響を与えずに、低コストで沈水植物群落を再生することができる。   According to the present invention, it is possible to easily regenerate a submerged plant community even in a water area with a large wave effect or in a large-scale lake, and it does not require a physicochemical apparatus such as a large plant or a medicine. Therefore, it is possible to regenerate submerged plant communities at low cost without adversely affecting the ecosystem of closed waters such as lakes.

また、本発明によれば、沈水植物群落の再生によって、湖沼等閉鎖性水域の水質を有効に浄化することができる。しかも、沈水植物群落の再生によって、水質浄化だけでなく、水鳥の餌としての機能、アオコを除去するミジンコなどの動物プランクトンの隠れ家機能、魚類の産卵礁機能、稚魚や底生動物の棲み家機能などによって、生態系の回復も期待することができる。   Moreover, according to this invention, the water quality of closed water areas, such as a lake, can be purified effectively by reproduction | regeneration of a submerged plant community. Moreover, by regenerating submerged plant communities, it not only purifies water quality, but also functions as a waterfowl food, zooplankton hideout function such as daphnia that removes sea cucumbers, spawning reef functions for fishes, and a habitat function for fry and benthic animals. The ecosystem can also be expected to recover.

以下、本発明に係る沈水植物群落の再生方法及びそれによる水質浄化方法の好ましい実施の形態について、図面を参照しながら説明する。図1は、本発明を工程順に示す説明図、図2は、本発明で適用する囲いの構造の一例を示す斜視図及び側面図、図3は、本発明で適用する囲い1の構造の他の例を示す斜視図及び側面図、図4は、囲い1の初期設置時の大きさを決定する方法を示す側面図、図5は、本発明において囲いを設置した初期状態を示す湖沼の平面図、図6は、本発明において囲い内で沈水植物が繁茂した状態を示す湖沼の平面図、図7は、本発明において沈水植物群落が再生された状態を示す湖沼の平面図である。   Hereinafter, preferred embodiments of a method for regenerating a submerged plant community and a method for purifying water according to the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing the present invention in the order of steps, FIG. 2 is a perspective view and a side view showing an example of a structure of an enclosure applied in the present invention, and FIG. 3 is another structure of the enclosure 1 applied in the present invention. FIG. 4 is a side view showing a method for determining the size of the enclosure 1 at the initial installation, and FIG. 5 is a plan view of a lake showing an initial state in which the enclosure is installed in the present invention. FIG. 6 and FIG. 6 are plan views of lakes and marshes showing a state in which submerged plants have grown in the enclosure in the present invention. FIG. 7 is a plan view of lakes and marshes showing a state in which submerged plant communities have been regenerated in the present invention.

本発明の方法では、まず図1における(A)に示されるように、初めに、沈水植物群落の再生対象の湖沼に、その水域の一部(以下、隔離水界という)aを他部(以下、外部水界という)bから隔離する囲い1を設置し、この囲い1による隔離水界aで沈水植物2を生育させる。   In the method of the present invention, first, as shown in FIG. 1 (A), first, a part of the water area (hereinafter referred to as an isolated water body) is transferred to another part ( The enclosure 1 isolated from b) is set up and the submerged plant 2 is grown in the isolated water area a.

初期設置時の囲い1による隔離水界aは、アオコ等植物プランクトンによる透明度の低い水質となっているため、隔離水界aに沈水植物2を確実に再生するには、隔離水界aの透明度を改善してから、沈水植物2を供給することが必要である。この場合の透明度改善方法としては、初期設置時の囲い1による隔離水界aの面積が小さいため、沈水植物2の成長を阻害するような薬剤等を用いる方法でなければどのような方法を用いて構わない。例えば先に従来技術として説明したバイオマニピュレーションによる方法や、水位制御による方法、植生浮島による方法や、水質浄化装置を用いる方法や、小型のプラントを用いる方法でも構わないし、囲い1の中に清浄水を供給して、汚濁水と入れ替える方法を用いても構わない。 Since the isolated water field a by the enclosure 1 at the initial installation has a low water quality due to phytoplankton such as blue-green algae, in order to reliably regenerate the submerged plant 2 in the isolated water field a, the transparency of the isolated water field a It is necessary to supply the submerged plant 2 after improving . As a method for improving the transparency in this case, any method is used as long as it is not a method using a drug or the like that inhibits the growth of the submerged plant 2 because the area of the isolated water boundary a by the enclosure 1 at the initial installation is small. It doesn't matter. For example, a biomanipulation method, a water level control method, a vegetation floating island method, a method using a water purification device, a method using a small plant, or a method using a small plant may be used. You may use the method of supplying and replacing with polluted water.

囲い1による隔離水界a内への沈水植物2の供給方法としては、対象水域内に残存している在来種や、この対象水域に流入する河川、又は対象水域から流出する河川など、周辺水域の河川等に自生している種に錘をつけるなどして散布する方法や、植生浮島を用いる方法でも良いし、水域の底泥中に眠る在来種の種子や殖芽などの土壌シードバンクを水底に撒き出す方法も採用可能である。   As a method for supplying the submerged plant 2 into the isolated water body a by the enclosure 1, there are local species remaining in the target water area, rivers flowing into the target water area, rivers flowing out of the target water area, and the like. Methods such as attaching weights to seeds that grow naturally in rivers in the water area, or using vegetation floating islands, or seeds of native species that sleep in the bottom mud of the water area or soil seeds such as sprouts It is also possible to adopt a method of rolling out the bank to the bottom of the water.

囲い1は、隔離水界aの四方を囲むものでも良いし、図1(A)のように、岸cを囲い1の一辺として他の三辺を囲む方法でも良い。隔離水界aの大きさは特に限定しないが、光条件が好ましくなる構造や、沈水植物2の再生目標規模と再生期間に応じて設定するのが好ましい。   The enclosure 1 may enclose four sides of the isolated water boundary a, or may be a method of enclosing the other three sides with the shore c as one side as shown in FIG. The size of the isolated water boundary a is not particularly limited, but is preferably set according to the structure in which the light conditions are preferable, the regeneration target scale of the submerged plant 2 and the regeneration period.

また、植物プランクトンの中でも最も水域の透明度を悪化させるのは、一般的にアオコと呼ばれる藍藻であり、これらのアオコは水面に粉状に発生する。このため、水面に浮かせた浮体にシート等を水面より50cm以深に下垂した構造でも、外部水界bよりも隔離水界a内の透明度を高く維持する効果を得ることはできるが、アオコ以外の植物プランクトンはそれよりも深い水深に分布できるため、水面から水底までを囲い込む構造とするのが最も好ましい。   In addition, it is a cyanobacteria generally called blue-green algae that most deteriorates the transparency of the water area among phytoplanktons, and these blue-green algae are generated in the form of powder on the water surface. For this reason, even in a structure in which a sheet or the like is suspended 50 cm or more deeper than the water surface on a floating body floated on the water surface, the effect of maintaining the transparency in the isolated water boundary a higher than the external water boundary b can be obtained. Since phytoplankton can be distributed at a deeper water depth, it is most preferable to have a structure that surrounds the water surface to the bottom of the water.

囲い1の構造は、隔離水界a内に、アオコ等の植物プランクトンが大量発生している外部水界bの汚濁水を流入させない構造であれば、どのようなものでも構わない。例えば、後述するように、土木工事等で用いられる鋼矢板や木板、杭、あるいは遮水シート等で囲う方法が考えられる。また、一般に植物プランクトンのサイズ分布の殆ど(8割以上)は2〜200μmであるため、透水性で粒径が2μm以上の粒子は通さない材料からなる膜又はシートで囲うことも好ましく、これによって、隔離水界a内へ、アオコ等の植物プランクトンで汚濁した水が流入するのを防止することができる。つまり、アオコが発生した汚濁水を隔離水界a内に流入させないためには、2μm以上の粒子が通らないもので囲うのが望ましく、また例えば近くに排水口があるような場合に、アオコが発生しやすい窒素やリンが非常に高濃度に含まれる汚濁水や、洗剤、又は農薬など沈水植物の生育に悪影響を与える物質が溶解した汚濁水を隔離水界a内に流入させないためには、遮水性の材質を選定することが望ましい。   The structure of the enclosure 1 may be any structure as long as it does not allow the contaminated water of the external water body b in which a large amount of phytoplankton such as sea cucumber is generated to flow into the isolated water field a. For example, as will be described later, a method of enclosing with a steel sheet pile, a wooden board, a pile, a water-impervious sheet, or the like used in civil engineering work is conceivable. Moreover, since most of the size distribution of phytoplankton (80% or more) is generally 2 to 200 μm, it is also preferable to surround with a film or sheet made of a material that is permeable and does not allow particles with a particle size of 2 μm or more to pass through. It is possible to prevent the water contaminated with phytoplankton such as the sea cucumber from flowing into the isolated water zone a. In other words, in order to prevent the polluted water that has been generated from flowing into the isolated water zone a, it is desirable to enclose it with something that cannot pass particles of 2 μm or larger. For example, when there is a drain outlet nearby, In order to prevent contaminated water containing very high concentrations of nitrogen and phosphorus that are likely to be generated and contaminated water in which substances that adversely affect the growth of submerged plants, such as detergents or agricultural chemicals, from flowing into the isolated water zone a, It is desirable to select a water-impervious material.

具体的な例としては、例えば図2に例示される囲い1は、水域の一部(隔離水界a)を取り囲んで他部(外部水界b)から隔離する囲い本体11と、この囲い本体11の上部を水面WLもしくは水面WL上に支持するためのフロート12と、囲い本体11の下部を水底Gに繋着するシートアンカー13と、フロート12をロープ又はワイヤ14を介して水底に繋着するフロートアンカー15とからなる。   As a specific example, for example, the enclosure 1 illustrated in FIG. 2 includes an enclosure main body 11 that surrounds a part of the water area (isolated water boundary a) and isolates it from the other part (external water boundary b), and the enclosure main body. The float 12 for supporting the upper part of the water 11 on the water surface WL or the water surface WL, the seat anchor 13 for connecting the lower part of the enclosure body 11 to the water bottom G, and the float 12 connected to the water bottom via a rope or wire 14 The float anchor 15

この構成において、囲い本体11は、水を通さず、又は透水性であるが2μm以上の粒子を通さない膜又はシートであれば素材を問わない。例えば、一般的に遮水シート材として、合成ゴム、塩化ビニル、ポリエステル、ポリエチレン、アスファルト系、ベントナイト系のものがあるので、対象水域の波、風、流速等の条件に応じてその素材、厚みを選定するのが好ましい。   In this configuration, the enclosure body 11 may be made of any material as long as it is a film or sheet that does not allow water to pass through or is permeable to water but does not pass particles of 2 μm or more. For example, generally there are synthetic rubber, vinyl chloride, polyester, polyethylene, asphalt type, bentonite type as the water shielding sheet material, so its material, thickness depending on conditions such as wave, wind, flow velocity etc. in the target water area Is preferably selected.

フロート12は、囲い本体11の重量を支えることのできる浮力を有するものであれば材質や種類を問わない。例えば、中空のプラスチック製の枠、あるいは発泡スチロールや発泡塩化ビニル等からなるブイや中空管状のものでも構わないが、容易に破損しないものを選択するのが好ましい。   The float 12 may be of any material or type as long as it has a buoyancy that can support the weight of the enclosure body 11. For example, a hollow plastic frame, a buoy made of foamed polystyrene or foamed vinyl chloride, or a hollow tubular shape may be used, but it is preferable to select a frame that does not easily break.

シートアンカー13は、囲い本体11が対象水域の波、流速、囲い本体11の浮力等によって水底Gから離れないものであれば、材質を問わない。例えば、鋼製のチェーン、鋼製の棒や管、鋼製の錘、砂利等を充填した土嚢等が好適に使用可能である。   The seat anchor 13 may be made of any material as long as the enclosure main body 11 is not separated from the water bottom G due to waves in the target water area, flow velocity, buoyancy of the enclosure main body 11 and the like. For example, a steel chain, a steel rod or tube, a steel weight, a sandbag filled with gravel, or the like can be suitably used.

フロートアンカー15は、水底Gに固定されるものであって、フロート12が水域の波、風、流速により流されないように、固定力を発揮するものであれば良い。例えば、鋼製やコンクリート製のブロックや錨、チェーン、土嚢などが好適に使用可能である。   The float anchor 15 is fixed to the bottom G, and may be any one that exhibits a fixing force so that the float 12 is not caused to flow by waves, winds, or flow velocities in the water area. For example, steel or concrete blocks, rivets, chains, sandbags, and the like can be suitably used.

また、囲い1は、フロート12及び囲い本体11の末端と末端を連結して隔離水界aを包囲する閉構造にすれば、囲い1を拡張する際に、その連結部をはずし、新たな拡張分を追加するだけで済むため、実用的である。また、汚濁防止膜やシルトフェンス、オイルフェンスとして既に市場に出回っている製品は、フロートと、粒径が5μm以上のシルトを通さないシートがセットになっているものがあるが、植物プランクトンのサイズや物理的な水域の条件に適合するならば、このような製品を用いても構わない。   Further, if the enclosure 1 has a closed structure in which the ends of the float 12 and the enclosure body 11 are connected to surround the isolated water boundary a, when the enclosure 1 is expanded, the connecting portion is removed and a new expansion is performed. This is practical because you only need to add minutes. In addition, products that are already on the market as antifouling films, silt fences, and oil fences include floats and sheets that have a particle diameter of 5 μm or more that do not pass through silt. Such products may be used as long as they meet the conditions of physical water bodies.

そして、図2に示される構造によれば、大きな土木工事は殆ど発生せず、囲い1の拡張作業や撤去作業も容易であるが、風、波、流速によって流されたりしないように、囲い本体11及びフロートアンカー15をしっかり固定する必要がある。   And, according to the structure shown in FIG. 2, the large civil engineering work hardly occurs and the expansion work and the removal work of the enclosure 1 are easy, but the enclosure main body is prevented from being swept away by wind, waves, and flow velocity. 11 and the float anchor 15 need to be firmly fixed.

一方、図3に例示される囲い1は、水域の一部(隔離水界a)を取り囲んで他部(外部水界b)から隔離する囲い本体11と、棒材又はパイプ材で組み立てられて囲い本体11が張設固定される支持枠16と、囲い本体11の下部を水底Gに固定するシートアンカー13とからなるものである。囲い本体11は、先に説明した図2の例と同様のものが使用可能である。   On the other hand, the enclosure 1 illustrated in FIG. 3 is assembled with an enclosure body 11 that surrounds a part of the water area (isolated water boundary a) and is isolated from the other part (external water boundary b), and a bar or pipe material. The frame includes a support frame 16 on which the enclosure body 11 is stretched and fixed, and a seat anchor 13 that fixes a lower portion of the enclosure body 11 to the water bottom G. As the enclosure main body 11, the same thing as the example of FIG. 2 demonstrated previously can be used.

支持枠16を構成する棒材又はパイプ材は、囲い本体11を支持可能で水底(底泥)Gに差し込むのに必要かつ十分な剛性があり、かつ水中で溶解、分解などにより劣化しないものであれば、鋼製、木製、プラスチック製等、材質を問わない。例えば、単管を単管クランプ等で図示の枠状に組み立てて、これに囲い本体11を張設する構成とすれば良い。また、シートアンカー13は、先に説明した図2の例と同様のものを選択することができる。   The bar material or pipe material constituting the support frame 16 is capable of supporting the enclosure body 11 and has sufficient and sufficient rigidity to be inserted into the water bottom (bottom mud) G, and does not deteriorate due to dissolution or decomposition in water. Any material such as steel, wood or plastic can be used. For example, a single tube may be assembled into a frame shape as illustrated with a single tube clamp or the like, and the enclosure main body 11 may be stretched over the frame. As the seat anchor 13, the same one as in the example of FIG. 2 described above can be selected.

図3に示される囲い1は、図2のものよりも大掛かりな構造であるが、水底G中に棒材又はパイプ材をしっかりと差し込んで支持枠16を組み立て、この支持枠16で囲い本体11を固定するため、強度の高い安定した構造とすることができる。   The enclosure 1 shown in FIG. 3 has a larger structure than that of FIG. 2, but a support frame 16 is assembled by firmly inserting a bar or pipe material into the bottom G, and the enclosure main body 11 is surrounded by the support frame 16. Therefore, a stable structure with high strength can be obtained.

したがって、図2のような構造にするか、図3のような構造にするかは、対象水域の特性に応じて選択するのが好ましい。また、更に他の例としては、鋼矢板や木板などによって、面状に組み立てるものであっても良い。   Therefore, it is preferable to select the structure as shown in FIG. 2 or the structure as shown in FIG. 3 according to the characteristics of the target water area. As still another example, the sheet may be assembled in a planar shape using a steel sheet pile or a wooden board.

囲い1の初期設置時の大きさを決定する方法としては、光条件に関しては、水深が深い水域の場合、初期設置時の囲い1の面積が小さいと沈水植物2の成育に十分な太陽光Sが届かなくなるため、次式(1)によって沈水植物2の成長に好ましい囲い1の一辺の初期長さを求めることが好ましい。
As a method of determining the size of the enclosure 1 at the time of initial installation, regarding light conditions, in the case of deep water, if the area of the enclosure 1 at the time of initial installation is small, the sunlight S sufficient for the growth of the submerged plant 2 Therefore, it is preferable to obtain the initial length of one side of the enclosure 1 preferable for the growth of the submerged plant 2 by the following formula (1).

この式(1)において、θは春分及び秋分時の南中高度である。すなわち、沈水植物が良く育つのは春〜秋にかけてであるため、式(1)は、図4に示されるように、春分及び秋分時に太陽の南中高度θで水底の80%以上に常に太陽光Sが当たるようにして沈水植物2の成長を高めるための望ましい設計条件である。例えばθ=54°である場合、水深1.5mの水域で囲い1の高さを2mとすると、囲い1の一辺の望ましい初期長さは約7.3m以上となり、囲い1が正方形である場合、その面積は、約53m以上となる。但し、囲い1の材質が太陽光Sを十分に通す素材である場合は、このような設計にする必要はない。 In this equation (1), θ is the south-central altitude at the time of spring equinox and autumn equinox. That is, since the submerged plants grow well from spring to autumn, as shown in FIG. 4, the equation (1) always shows the sun at 80% or more of the bottom of the water at the south and middle altitudes of the sun at the spring and autumn minutes. This is a desirable design condition for increasing the growth of the submerged plant 2 by being exposed to light S. For example, when θ = 54 °, if the height of enclosure 1 is 2 m in a water area with a water depth of 1.5 m, the desired initial length of one side of enclosure 1 is about 7.3 m or more, and enclosure 1 is square The area is about 53 m 2 or more. However, when the material of the enclosure 1 is a material that allows the sunlight S to sufficiently pass therethrough, it is not necessary to make such a design.

また、沈水植物2の再生目標規模と期間に応じた囲い1の初期設置時の好ましい大きさは、次式(2)及び(3)によって導くことができる。
Moreover, the preferable magnitude | size at the time of the initial installation of the enclosure 1 according to the reproduction | regeneration target scale and period of the submerged plant 2 can be guide | induced by following Formula (2) and (3).

上記式(2)において、対象水域の面積とは、沈水植物群落の再生を対象とする閉鎖性水域(図5〜図7に示される湖沼L)の面積である。目標再生率は、対象とする閉鎖性水域に沈水植物群落を再生する割合、つまり目標再生規模であり、これは対象水域への流入、流出水の水量と水質、水域の滞留時間、水域内での水の流動、対象水域内の物質循環等を考慮した水質予測モデル等において設定するのが最も望ましいが、簡易的には、対象水域面積に対して10〜40%に設定しても良い。すなわち、沈水植物群落が、対象水域面積に対して10〜40%の面積を占有した状態に再生されれば、効果的な水質浄化作用が期待できる。   In the above formula (2), the area of the target water area is the area of the closed water area (lake L shown in FIGS. 5 to 7) targeted for the regeneration of the submerged plant community. The target regeneration rate is the rate at which submerged plant communities are regenerated in the target closed water area, that is, the target regeneration scale. This is the inflow to the target water area, the amount and quality of the effluent water, the residence time of the water area, and within the water area. It is most desirable to set in a water quality prediction model that takes into account the water flow, material circulation in the target water area, etc., but may be set to 10 to 40% with respect to the target water area. That is, if the submerged plant community is regenerated to occupy an area of 10 to 40% of the target water area, an effective water quality purification action can be expected.

また、上記式(2)において、拡大回数は年間拡大回数に目標期間を乗じ、最初の囲い分を引いた値となる。年間拡大回数は、植物種、対象水域の水質、底質条件等によって異なるが、一般的には年に1回又は2回、多くても3回と設定するのが好ましい。   In the above formula (2), the number of expansions is a value obtained by multiplying the number of annual expansions by the target period and subtracting the first enclosure. The number of annual expansions varies depending on the plant species, the water quality of the target water area, bottom sediment conditions, etc., but it is generally preferable to set the number of annual expansions once or twice a year and at most three times a year.

なお、上記式(2)及び(3)に基づいて、例えば沈水植物を再生する対象湖沼の面積を1km(1000,000m)とし、設定値を仮に以下のように設定して計算すると、開始時の囲いの好ましい大きさは1,600mとなる。
対象水域の面積:1000,000m
目標再生率:20%
囲いの拡大率:5倍/回
目標期間:5年
拡大回数:1回/年
Based on the above formulas (2) and (3), for example, assuming that the area of the target lake where the submerged plant is regenerated is 1 km 2 (1,000,000 m 2 ) and the set value is set as follows, The preferred size of the starting enclosure is 1,600 m 2 .
Target water area: 1,000,000m 2
Target regeneration rate: 20%
Enlargement rate of enclosure: 5 times / time Target period: 5 years Expansion frequency: 1 time / year

説明を図1に戻すと、図1(A)に示される初期設置時の囲い1による隔離水界a内では、アオコ等の植物プランクトンが発生した汚濁水の流入が、囲い1によって防止され、かつ波浪も囲い1によって有効に遮断されるので、沈水植物2の成長が妨げられない。したがって、図1(B)に示されるように、やがて隔離水界a内には沈水植物2が繁茂して群落を形成する。   Returning to FIG. 1, in the isolated water area a by the enclosure 1 at the initial installation shown in FIG. 1 (A), the inflow of polluted water in which phytoplankton such as sea lions is generated is prevented by the enclosure 1. Moreover, since the waves are also effectively blocked by the enclosure 1, the growth of the submerged plant 2 is not hindered. Therefore, as shown in FIG. 1 (B), the submerged plants 2 will eventually grow in the isolated water boundary a to form a community.

沈水植物2の群落が、囲い1による隔離水界a内の全面に繁茂するまでの期間は、囲い1の規模と、対象の閉鎖性水域(湖沼L)の水質や底質等の特性、沈水植物2の供給量などによって異なるが、沈水植物2の群落が隔離水界a内の全面に繁茂したら、図1(C)又は図5に示されるように、囲い1を拡張する。この場合、大きな囲い1を新たに施工しても良いが、既設の囲い1を開放し、その開放された連結部1aに、新たに拡張する部分の連結部1bを連結するのが経済的である。   The period until the community of the submerged plant 2 grows over the entire surface of the isolated water area a by the enclosure 1 is the size of the enclosure 1 and the characteristics of the target closed water area (Lake L), such as water quality and bottom quality, Although it depends on the supply amount of the plant 2, etc., when the community of the submerged plant 2 grows over the entire surface of the isolated water boundary a, the enclosure 1 is expanded as shown in FIG. 1 (C) or FIG. In this case, the large enclosure 1 may be newly constructed, but it is economical to open the existing enclosure 1 and to connect the newly expanded portion of the connecting portion 1b to the opened connecting portion 1a. is there.

このとき、拡張率をどの程度にするかは、閉鎖性水域の特性に応じて、水質予測モデル等で予測するのが最も望ましいが、先に説明した初期設置時の囲い1の大きさ設定と同様の考え方から、簡易的には、拡張後の隔離水界aの面積に対する群落の占有面積が10〜40%となるように、拡張率を2.5〜10に設定することが好ましい。その理由は、沈水植物2の群落の面積が全体の10〜40%占有した状態において、この沈水植物2の群落による浄化作用により拡張後の隔離水界aの透明度が有効に改善されるからである。拡張率を、この範囲を超える倍率に設定した場合は、群落の占有面積が過小であるため、拡張によって悪化した隔離水界aの透明度が改善されにくく、沈水植物2の成育に必要かつ十分な太陽光が水底に届かないため、群落の拡大が遅延するか、最悪の場合は再生した沈水植物群落が再消失するおそれがある。   At this time, it is most desirable to predict the extent of expansion by using a water quality prediction model or the like according to the characteristics of the closed water area, but the size setting of the enclosure 1 at the time of initial installation described above From the same idea, it is preferable to set the expansion rate to 2.5 to 10 so that the area occupied by the community with respect to the area of the isolated water boundary a after expansion is 10 to 40%. The reason is that, in the state where the area of the community of the submerged plant 2 occupies 10 to 40% of the whole, the transparency of the isolated water boundary a after expansion is effectively improved by the purification action by the community of the submerged plant 2. is there. When the expansion rate is set to a magnification exceeding this range, the occupied area of the community is too small, so the transparency of the isolated water boundary a deteriorated by expansion is difficult to improve, and is necessary and sufficient for the growth of the submerged plant 2. Since sunlight does not reach the bottom of the water, the expansion of the community is delayed, or in the worst case, the regenerated submerged plant community may disappear again.

上述のように、拡張後の隔離水界aの面積に対する群落の占有面積が10〜40%となるように囲い1を拡張すれば、拡張によって隔離水界aの水質が一時悪化しても、沈水植物2の自然浄化機能によってすぐに透明度が改善されるため、囲い1により面積が拡大した隔離水界a内で、図1(D)又は図6に示されるように、沈水植物2の群落が拡大していく。   As described above, if the enclosure 1 is expanded so that the occupied area of the community with respect to the area of the isolated water boundary a after expansion is 10 to 40%, even if the water quality of the isolated water boundary a is temporarily deteriorated by the expansion, Since the transparency is immediately improved by the natural purification function of the submerged plant 2, the community of the submerged plant 2 in the isolated water area a whose area is expanded by the enclosure 1, as shown in FIG. Will expand.

拡張した囲い1による隔離水界aの全域に沈水植物2の群落が繁茂したら、再び囲い1を拡張し、沈水植物2の群落を繁茂させる。そして、このような工程を繰り返していくことによって、図7に示されるように、最終的には閉鎖性水域(湖沼L)において、目標とする再生面積まで沈水植物2の群落を再生することができる。目標とする再生面積まで沈水植物2の群落が拡大した後は、囲い1を撤去しても沈水植物2の自然浄化機能が作用が高いため、沈水植物2の群落が消失することはなく、むしろ拡大していく。また、再生した沈水植物2の群落によって、対象水域の水質及び生態系を含めた水環境を急速に回復することができる。   When the community of the submerged plant 2 grows in the whole area of the isolated water boundary a by the expanded enclosure 1, the enclosure 1 is expanded again and the community of the submerged plant 2 grows. And by repeating such a process, as shown in FIG. 7, finally in the closed water area (lake L), the community of the submerged plant 2 can be regenerated to the target reclaimed area. it can. After the settlement of the submerged plant 2 has expanded to the target regeneration area, even if the enclosure 1 is removed, the subsidence plant 2 community will not disappear because the natural purification function of the submerged plant 2 is high. Expand. Moreover, the water environment including the water quality and ecosystem of the target water area can be rapidly recovered by the community of the regenerated submerged plant 2.

本発明を工程順に示す説明図である。It is explanatory drawing which shows this invention in process order. 本発明で適用する囲いの構造の一例を示すもので、(A)は斜視図、(B)は側面図である。An example of the structure of the enclosure applied by this invention is shown, (A) is a perspective view, (B) is a side view. 本発明で適用する囲いの構造の他の例を示すもので、(A)は斜視図、(B)は側面図である。The other example of the structure of the enclosure applied by this invention is shown, (A) is a perspective view, (B) is a side view. 本発明で適用する囲いの初期設置時の大きさを決定する方法を示す側面である。It is a side view which shows the method of determining the magnitude | size at the time of the initial installation of the enclosure applied by this invention. 本発明において囲いを設置した初期状態を示す湖沼の平面図である。It is a top view of the lake which shows the initial state which installed the enclosure in this invention. 本発明において囲い内で沈水植物が繁茂した状態を示す湖沼の平面図である。It is a top view of the lake which shows the state where the submerged plant grew in the enclosure in the present invention. 本発明において沈水植物群落が再生された状態を示す湖沼の平面図である。It is a top view of the lake which shows the state where the submerged plant community was reproduced | regenerated in this invention.

符号の説明Explanation of symbols

1 囲い
1a,1b 連結部
11 囲い本体
12 フロート
13 シートアンカー
14 ロープ又はワイヤ
15 フロートアンカー
16 支持枠
2 沈水植物
a 隔離水界(水域の一部)
b 外部水界(水域の他部)
L 湖沼(閉鎖性水域)
DESCRIPTION OF SYMBOLS 1 Enclosure 1a, 1b Connection part 11 Enclosure main body 12 Float 13 Seat anchor 14 Rope or wire 15 Float anchor 16 Support frame 2 Submerged plant a Isolation water body (a part of water area)
b External water (other parts of water)
L Lake (closed water area)

Claims (9)

水域内に、この水域の一部を他部から隔離する囲いを設けて、この隔離された水域の透明度を改善してから、前記隔離された水域の中で沈水植物を生育させ、前記沈水植物の群落が前記隔離された水域における所定の面積まで成長したら、前記囲いによって隔離する水域の面積を適宜拡大して引き続き前記沈水植物を生育させるといった工程を繰り返すことを特徴とする、沈水植物群落を再生する方法。 An enclosure for isolating a part of the water area from the other part is provided in the water area, and after improving the transparency of the isolated water area, a submerged plant is grown in the isolated water area, and the submerged plant When the community grows up to a predetermined area in the isolated water area, the area of the water area isolated by the enclosure is appropriately expanded and the process of continuously growing the submerged plant is repeated. How to play. 囲いが、水面から50cm以深を囲うものであることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The method for regenerating a submerged plant community according to claim 1, wherein the enclosure surrounds a depth of 50 cm or more from the water surface. 囲いが、水面から水底までを囲うものであることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The method for regenerating a submerged plant community according to claim 1, wherein the enclosure surrounds the water surface to the bottom of the water. 囲いが、粒径が2μm以上の粒子を通さない材質からなることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The method for regenerating a submerged plant community according to claim 1, wherein the enclosure is made of a material that does not pass particles having a particle diameter of 2 μm or more. 囲いが、遮水性を有する材質からなることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The method for regenerating a submerged plant community according to claim 1, wherein the enclosure is made of a material having water-impervious properties. 囲いが、囲い本体と、この囲い本体の上部を水面もしくは水面上に支持するためのフロートと、前記囲い本体の下部を水底に繋着するシートアンカーと、前記フロートを水底に繋着するフロートアンカーとからなることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   An enclosure is an enclosure body, a float for supporting the upper part of the enclosure body on the water surface or the water surface, a seat anchor for joining the lower part of the enclosure body to the bottom of the water, and a float anchor for joining the float to the bottom of the water The method for regenerating a submerged plant community according to claim 1. 囲いが、囲い本体と、この囲い本体を固定する支持枠と、前記囲い本体の下部を水底に固定するシートアンカーとからなることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The method for regenerating a submerged plant community according to claim 1, wherein the enclosure comprises an enclosure body, a support frame for fixing the enclosure body, and a seat anchor for fixing a lower portion of the enclosure body to the bottom of the water. . 囲いの拡大は、この囲いによって隔離される水域の面積に対して、前記囲い内の沈水植物群落の占有面積が10〜40%が確保されるようにすることを特徴とする請求項1に記載の沈水植物群落を再生する方法。   The enlargement of the enclosure is characterized in that 10 to 40% of the occupied area of the submerged plant community in the enclosure is secured with respect to the area of the water area isolated by the enclosure. To regenerate submerged plant communities. 請求項1〜8のうちいずれかの方法により再生される沈水植物群落によって閉鎖性水域の水質を浄化することを特徴とする水質浄化方法。   The water quality purification method characterized by purifying the water quality of a closed water area by the submerged plant community regenerated by the method in any one of Claims 1-8.
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