A METHOD OF CLEANING Technical Field [1] The present invention concerns the method of naturally purifying polluted rivers. More specifically, the invention is about the method of installing a multiple-staged discharge system along the length of the river to naturally purify the river. The system is operated either by water pressure or motor power. [2] It is a well-known fact that streams of water flow into water storage such as rivers and water reservoirs from various channels. Then, it also follows that at least one of those channels contains pollutants in masse. [3] Therefore, there have been many methods suggested so far in the purification of such bodies of water. The rapid sand filter, slow sand filter, water purification by the methods used for sewage treatment, and chlorine treatment are some types of methods that have been used until now. However, all of the above stated methods cost con¬ siderable amounts of money and we claim that they have not proven as effective as the amount of money put into them. [4] In order to improve these shortcomings, a device has been suggested that purifies the river by making whirlpools in the water which in turn causes the pollutants to float to the surface. Then the pollutants could be lifted out. However, the cons of this device were that a separate apparatus was required and that the area in which the device could operate in was very limited. And so, the device did not prove at all useful in wide areas that needed purification. [5] The present invention is about technology that purifies the rivers that are getting polluted all the more day by day. The purification is done by natural means. Background Art [6] The present applicant for the patent has another patent under the name, "Natural Pu¬ rification Method of water by using Multiple-staged Reservoir Device." The patent received Korean Patent Public No. 2001-0000343. This present invention is of technology that is one step ahead of the applicant's previous patent. In the previous patent, only one water gate was present and so it had a fault of having very low natural self-purification effect caused by aeration. [7] Because of this fault, water stored within the interiors of the water gate would combine with pollutants and this in turn would cause the lumping effect and the combining effect of matter. These effects would raise the pollution level of the water and would induce green tide. Therefore, the fault of the previous patent had a serious problem of worsening the condition of the stored water. [8] In order to raise the technological worth of the present invention, the terms applied to the present invention shall be explained. [9] The following terms relate to phenomenon which either purifies pollutants in the rivers or worsens the pollution level. These terms shall be explained: "acceleration phenomenon of matter", "cut in effect of matter", "law of matter conservation instinct", "lumping effect", "combination effect of matter", "rejection effect of matter", and "separation effect of matter." [10] When a multiple-stage discharge system having both an aeration device-type main water gate and an auxiliary water gate is installed along the river, the above mentioned effects are aroused and they naturally purify polluted rivers. The reason is because of the following effects that occur. [11] The "acceleration phenomenon of matter" which corrodes stored water shall be explained. [12] All matter, because of the difference in its mass and relative density, form different layers as soon as it flows into water according to each matter's mass and relative density. In other words, heavier matter will form the bottom layer while lighter matter will float to the top. And these different layers of matter will form the flow of water. [13] Because of this effect, clean water ? which has a high relative density, forms the lower layer of the river in its flow and polluted waters ? which has a low relative density, flows in the top layers of the river. Reality is that the flow speed of the river is faster in the upper layers ? which are polluted, then the lower layers or the clean water. The reason for the occurrence of this effect is that the amount of pollutants in the river, i.e. the pollutant load is high. [14] In the present invention, the above principle is called the "acceleration phenomenon of matter." [15] The increase of the pollution level in rivers is due to the "acceleration phenomenon of matter" and the "lumping effect." The reason is because of the following phenomenon. [16] Gravitation occurs because of the revolution of the earth and the solar system. Due to gravitation, the polluted waters which has a lower relative density flows on top of the clean waters which as a higher relative density. Then as the water flows down the river, other polluted waters constantly flow into the river and join in with pollutants already present in the water. This is turn causes the lumping effect and worsens the pollution of the river. Therefore, the pollution level of the river is increased. [17] Then, the "acceleration phenomenon of matter" can be defined in the following manner: it is a phenomenon in which the polluted waters of the river with a lower relative density stays on top of those waters with higher relative density and flows faster down the river than the lower layers. [18] Next, the "cut in effect of matter" shall be explained. This effect occurs when the water purification system of the present invention is installed along the whole river in order to prevent the "acceleration phenomenon of matter." The "cut in effect of matter" shall be explained in detail. [19] The cut in effect of matter and the acceleration phenomenon of matter have a very close relationship with each other. [20] The cut in effect of matter occurs in the following manner: when the polluted river passes through each stages of the aeration-causing water gate system installed by the construction of the present invention, the clean waters of the river with the higher relative density pushes the polluted water with the lower relative density up to the top layers. Next, the clean waters escape out of the discharge system of the aeration- causing water gate before the polluted waters. In the present invention, this principle is named with the term "cut in effect of water." [21] All matter that exists on earth, even if the atoms and the molecules that form the matter are same in size, differ in their volume or relative density. Therefore, once the matter is put into water, each matter assumes a different position in water. [22] The present invention is about purifying a polluted river by using the "cut in effect of matter" that occurs because of the above stated fact. In other words, when the river passes through each stages of the multiple-staged discharge system, clean waters with higher relative density pushes polluted waters with lower relative density to the top layers and then escapes first out of the system. This effect is defined as the "cut in effect of matter" in this present invention. [23] More precisely, in the present invention, to prevent the occurrence of the ac¬ celeration phenomenon of matter which increases the pollution level of water, aeration- causing water gates are installed along the whole length of the river in multiple stages. Then, the water gates increase the efficiency of the cut in effect of matter. At the same time, so that the aeration effect may be incurred, the aeration-causing water gates are installed at each different levels of the river. Thus, the present invention consists of two parts: one multiple-staged discharge system and one composite control system. [24] Next, the following terms are explained: "the law of matter conservation instinct", "lumping effect", and the "delivery effect of matter." "The law of matter conservation instinct" is caused by the fact that all matters, by instinct, try to conserve its original elements. Because of this law, the "lumping effect" is incurred. The "delivery effect of matter" is caused by the aeration effect. [25] Water, because of its structural characteristic, when a matter other than water in¬ filtrates into the structure of the water, water instinctively accepts that infiltrating matter, combines with that matter and forms another matter. [26] In the present invention, the above effect is defined as the "lumping effect." [27] Also, in order to get rid of the pollutants that have infiltrated into the pure water molecular structure which form water crystals, constant amount of shock is given to water. Then, because of the shock, the pollutants contained within the pure water molecular structure immediately separate from the structure. This occurrence is defined as the "separation effect of matter." The basic principle behind the occurrence of this effect is the "law of material conservation instinct" as defined in the present invention. [28] In other words, when the system of the present invention is installed, the whirlpool and the aeration effect is incurred. These two effects give physical shock to water and clean up the polluted water. The overall effect is defined as the "separation effect of matter." [29] As is stated above, when water is discharged from a reservoirs which stores up water from rivers, if it is discharged from the upper part with systems such as concrete weirs, conductive water gates, or rubber dams, then the lumping effect will occur and increase pollution level of the water. However, when the water gate system is installed which discharges the river from the lower part of the reservoir, the cut in effect of matter and push effect of matter along with separation effect of matter will naturally occur and all work together to naturally purify the polluted river. [30] If reservoir devices constructed according to the method presented in this invention are installed within large-sized dams or in the upper part of the river that flows towards the dams, then because of the cut in effect of matter, polluted waters of the river will not be able to flow into the dams. Therefore, this would be of significant help in solving the problem of polluted rivers locked up within dams by removing the problem at its source. [31] If rubber dams and conductive water gates are installed to discharge only part of the waters in the lower layer of the river and concrete weirs are installed which discharge the water through the upper part of the dam, then the pollution level is increased. The reason why shall be explained. [32] Polluted waters with a lower relative density are accumulated on the parts of the rubber dam or the conductive water gate that do not constitute the discharge area. Then, these waters, because of the push effect of matter, are pushed out by the clean waters with a higher relative density. The problem is that they are pushed not out of the discharge area but into other parts. Then, due to the lumping effect, these polluted waters combine again with other pollutants and thus the pollution level is all the more increased. [33] The polluted waters of the river are accumulated in parts of the water gate besides the discharge area because of the push effect of matter and the lumping effect. Due to structural problems, it is impossible for these polluted waters to flow down the river. Then the accumulated waters combine with other matters and pollutants within the waters lump together and so the pollution level is increased furthermore. This is because when a siphon-type water gate which allows only a part of the water in the lower layers to be discharged is installed, clean waters with a higher relative density flows out of the discharge system before the polluted waters due to the cut in effect of matter. Then the polluted waters are left behind and are stagnant and because of the push effect of matter can never flow out down the river. The waters once again lump with other pollutants because of the lumping effect and therefore the state of the polluted waters gets all the more worse. [34] If water is store using the rubber dam, the conductive water gate, and the concrete weir, then, while the water is stored within the weir, a serious problem arises in that the pollution level increases because of the "lumping effect" and the "combining effect of matter." [35] Next, the "rejection effect of matter" shall be explained. [36] All matter, as it enters water, is diluted. The lumping effect and the combining effect of matter do not occur at first. However, because of the rejection effect of matter, the pure water molecule structures reject the pollutants. Therefore, combining does not happen immediately. In other words, at first, the water molecules reject the lumping effect which makes matters to lump together. But after a certain period of time has passed, due to natural causes such as dissolved oxygen, the sun's heat, mi¬ croorganisms, and effect of osmotic pressure, the water molecules are decomposed. Then, the pollutants slowly begin to combine with the water molecules causing the combining effect of matter and the pollution level is increased. [37] Next, the process by which polluted waters are purified through the principle of the "law of matter conservation instinct" shall be explained. [38] The pure molecules of water, because of the law of matter conservation instinct, try to maintain their structure and reject to be combined with other matters that are polluted. However, because of the viscosity of the pollutants, the water molecules cannot help but combine with other matters. As combination occurs, the relative density of the water gets higher and sinks to the bottom layer of the river. And then, because of decomposition caused by natural means, the decomposed water molecules along with partial matter of the pollutants once again rise to the upper layer of the reservoir. Then, this step repeats itself over and over again. Water molecules combine with pollutants, sink to the bottom, are decomposed by natural means, rise to the top, and so on. In this way, the river becomes purified. In the present invention, the cause of the above process is what is defined as the "law of matter conservation instinct." [39] The present invention either incurs or stops the above mentioned effects: the "acceleration phenomenon of matter", "cut in effect of matter", "law of matter con- servation instinct", "lumping effect", "combining effect of matter", "rejection effect of matter", "separation effect of matter", and the "decomposition effect of matter." By doing so, this invention allows for the natural purification of polluted rivers by solving the problem at its roots. Disclosure of Invention Technical Problem [40] Water gates for aeration are installed in multiple stages between the embankments of the river along the whole length of the river. Then, as water is discharged from the water reservoir, so that aerations and whirlpools can be incurred between each main water gate and secondary water gate, a discharge system in multiple stages is installed. Due to this installation, oxygen from the air is naturally supplied into the water. In turn, this supply of oxygen causes natural aeration effects. Then, following the aeration effects, the "acceleration phenomenon of matter, " "cut in effect of matter", "law of matter conservation instinct", "lumping effect", "combining effect of matter", "rejection effect of matter", "separation effect of matter", and the "decomposition effect of matter" occur. By either using or suppressing these effects, the present invention wishes to provide a method of purifying a polluted river. [41] Another point of view is this. Each water gate is equipped with a motor power transmitting system. Then each motor power transmitting system would be controlled by a central control system and by controlling each aeration-causing water gate according to the level of pollution in the water reservoir, purification of water could be done in a more aggressive manner. The enactment of this system is seen as another major technological task. Technical Solution [42] For the technological solution of the present invention, the main aeration-causing water gate and the secondary aeration-causing water gate are installed. Also, aeration materials (5) are attached to the upper exterior of the aeration-causing water gate so that more aerations and whirlpools may be incurred between the water gates. The in¬ stallations and the attachments are the solutions to the technical problems. [43] Also, because water flows horizontally by each layer of matter, an aeration-causing water gate should be installed along the whole width of the river so that only the bottom layer of the river may be discharged. For an alternative, a siphon passage or a conductive-type water gate in addition to a secondary water gate may be installed so that much of the bottom layer is discharged. Another alternative is to install a discharge system that lets out the bottom layer of the river in the lower part of a rubber dam. The rubber dam would be installed along the whole width of the river. By installing one of the devices stated above, the polluted river may be naturally purified. In this way, the technical problems can be solved. Advantageous Effects [44] As it has been explained so far, the present invention is constructed in a way so that water could be discharged through the lower parts of a multiple-stage water gate. The natural water purification method of the present invention that makes use of the multiple-stage aeration system has the following significant effect. Because of the aeration system, the "acceleration phenomenon of matter, " "cut in effect of matter", "law of matter conservation instinct", "lumping effect", "combining effect of matter", "rejection effect of matter", "separation effect of matter", and the "decomposition effect of matter" naturally occur. These effects in turn work to naturally purify the river of the pollutants contained in it. The polluted river could be cleaned up from its roots. [45] In other words, while the polluted water stays in reservoirs, it becomes naturally purified. Not only that, by blocking the lumping effect, the system prevents from secondary pollution due to the formation of new pollutants. Also, as water is discharged, whirlpools are incurred between the main water gate and the secondary water gate. During the process of incurring the whirlpools, the aeration effect is also incurred. Then, along with the natural purification effect of the water itself, the separation effect of matter which occurs naturally when the aeration effect occurs induce pollutants to rise to the top. So a more aggressive water purification process could be performed. These water gates are installed in multiple stages. And so, as water flows through each stage, it could be more surely purified by natural means. [46] Therefore, when this kind of system is applied, even large rivers can easily be purified with low expenses. And because purification system which is naturally incurred is used, the river could be purified to a clean and pure state. The system has an effect of producing clean water without the aid of chemicals such as chlorine or fluoride. If the system is applied to large-sized dams, the accumulation of slime that builds up within the interiors of the dam could be removed. Also, the system would have a significant effect in preventing green tide that occurs because of such effects as the accumulation of slime. [47] The system could also prevent red tide. Red tide is caused by the flow of polluted rivers into the sea. By purifying the river, the system could eliminate the source of red tide. [48] Another advantage of the invention is this. No matter how much water is stored, it does not get polluted. So that means water can be stored in mass amounts. Then, because of the capillary phenomenon caused by the stored water, the mountains and fields nearby would maintain a high level of moisture in the land which would make the land fertile. This would mean that there would be abundance come harvest time. Also, because of the capillary phenomenon, the growth of plants in the mountains would be stimulated which in turn would be of significant help in preventing landslides. Therefore, because of the effects caused by the stored water, desertification due to draughts can be prevented and deserts can also be changed to fertile land. Brief Description of the Drawings [49] Figure 1 : Structure of river purification device according to the present invention [50] Figure 2: Structure of device in Figure 1 in case motor power is attached [51] Figure 3: Structure of river purification device according to the alternative example suggested in the present invention [52] Figure 4: Structure of device in Figure 4 in case motor power is attached [53] *** Explanation of Symbols on main parts of the figures *** [54] 1 : embankment wall 5: aeration material 10 : aeration-causing main water gate [55] 20 : aeration-causing secondary water gate 30 : aeration-causing multiple-stage water gate [56] 40 : motor power transmitting system 50 : central control system Best Mode for Carrying Out the Invention [57] In the following, the first working example suggested by the present invention shall be explained in detail. The attached figure shall be referred to. [58] As it is shown in Figure 1, the river purification system of the present invention is one in which the aeration-causing water gate is installed in the direction of water discharge along the wall of the embankment (1). As for the aeration-causing water gate, the center of rotation is located on the upper part and is installed in a way so that it slants toward to direction of water discharge. It is constituted of the following parts: the main aeration-causing water gate (10) which discharges the water through the lower part and the multiple-stage secondary aeration-causing water gates (20). The upper part of each secondary water gate is fixed onto the exterior part of the main aeration-causing water gate (10) so that revolution is possible. Therefore, this con¬ struction makes possible the occurrence of whirlpools between the main aeration- causing water gate (10), the secondary aeration-causing water gates (20), and another supportive aeration-causing water gate when water is discharged from the water reservoir. [59] The aeration-causing water gates (10) (20) which are constructed according to the above stated structure, can be made in a way so that they automatically open according to water pressure. As shown in Figure 2, a motor power transmitting system (40) is connected to each of the main aeration-causing water gate (10) and the secondary aeration-causing water gates. Then a central control system (50) which controls each motor power transmitting system (40) is constructed. The central control system could be manipulated in a way so that it controls the opening, closing, and patterns of each aeration-causing water gate (10) (20) according to the pollution level in the water reservoir. [60] Because of the above stated constructions, a polluted river can be purified by natural means. The polluted river is purified by the following effects. [61] First, in the case each of the aeration-causing water gates (10)(20) are constructed so that they automatically open due to water pressure, when a certain amount of water fills up the reservoir so that the water pressure exceeds the closing pressure of the aeration-causing water gates (10) (20), then that water pressure pushes out the water gates and water is discharged through the space made between the lower part of each aeration-causing water gate (10)(20) and the floor. [62] At this time, the water which was discharged by pushing out the main aeration- causing water gate (10) has to once again push out the secondary aeration-causing water gate (20). During this process, whirlpools are incurred in the water and because of the occurrence of whirlpools oxygen from the air is naturally supplied into the water causing the aeration effect. Due to the aeration effect, pollutants in the water rise up to the top. [63] Also, the water that was discharged out of the secondary aeration-causing water gate (20) has to push out yet another supportive aeration-causing water gate on the outside (20). As this process is repeated, whirlpools are incurred between each of the aeration-causing water gates (10)(20) and the water gradually gets cleaner. When at last the water is discharged out of the final supportive aeration-causing water gate (20), it is at a purified state. The pollutants which have risen to the top will be gradually purified after continuous discharge of water because of the self-purification char¬ acteristic of water. [64] In addition, water has a self-purification characteristic of its own. The present invention stimulates that characteristic. In the following, the characteristic of water will be explained. [65] There exist millions of kinds of matter all around the world. All of those matters either oxidizes or decays in the natural environment they are in. As they do so, the matters lose their original form. During the process of oxidization or decay, the matters that have been oxidized or decayed join rainwater and flows into natural rivers. [66] However, because of the difference in the number of elements and number of carbons contained in the matters themselves, the matters do not completely decay or oxidize. They contain a little bit of carbon and elements and it is in this state that the matters flow into water. Therefore, each matter has a different relative density. And it is according to this relative density that the matters begin to flow in water in different layers. This effect is caused by the centrifugal force which occurs as the earth revolves around the sun. Because of the centrifugal force, the clean waters with a higher relative density flows in the bottom layers of the river while the polluted waters with a lower relative density flow in the top layers. In addition, the clean waters with a higher relative density push the polluted waters to the top and flow out at a faster speed. [67] When water flows naturally as described above, whirlpools are incurred between each water gate. Then, the clean waters with the higher relative density would push aside the polluted waters with a lower relative density and would pass through the lower parts of each aeration-causing water gate. During this process, oxygen from the air is naturally put into the water. Then, the amount of dissolved oxygen is increased. This increase causes the aeration effect which in turn purifies the polluted water. [68] Also, when water is stagnant, matters beside water combine with the structure of water and infiltrates into the water. Then, because of its structural characteristic, water accepts the infiltrating matter and combines with that matter. And so the pollution level is increased. However, if constant amount of shock is given to the water at this state, then the infiltrating matter separates and water molecules have the characteristic of bonding with each other. [69] Therefore, as water is discharged, it crashes against each aeration-causing water gate (10)(20) and during the process of incurring whirlpools, shock is given to pollutants and polluted waters which are in combination with the pollutants. Then the shock process to separate the pollutant is done naturally. In other words, the separation effect of matter occurs and water is purified. Due to this effect, as pollutants rise to the top layers of the water, water molecules bond together and the purifying process of water occurs. [70] The summary of the above is the following. Water flows in layers according to the relative density of the matters contained in the water. As the water crashes against the main aeration-causing water gate (10) and the secondary aeration-causing water gates (20), whirlpools are incurred and so oxygen in the air is naturally supplied into the water. Then the amount of dissolved oxygen in the water is increased. Due to the increase, pollutants that were part of the water molecules are separated away. Clean water molecules bond together. Also, pollutants with a lower relative density are induced to rise to the top by aeration. In this way, purification takes places. This process takes place successively between each aeration-causing water gate (10) (20). And so the water is gradually purified. [71] However, if a conductive-type or a rubber dam or a concrete weir is used instead of the aeration-causing water gate (10) (20) mentioned in the present invention, there is a problem that the pollution level is increased. This is because while the water gate of the present invention discharges water from the lower part, the other types discharge water from the upper part. If water is discharged from the upper part, the polluted waters with a lower relative density are accumulated in areas other than the discharge area. Then because of the push effect of matter, the polluted waters are pushed into places other than the discharge area by the clean waters with the higher relative density. Then the polluted waters come to a state in which it is impossible for them to move down the river. In this state, the polluted waters combine with other pollutants and the pollution level is increased. [72] However, if aeration-causing water gates which discharge water from its lower parts are installed along the whole width of the river, then the polluted rivers can be naturally purified. The principle is as follows: ® Effect of solar heat ? ultraviolet and visible rays from the sun naturally purifies the polluted water, (D natural purification effect caused by surface friction from contact of air with water, (D water purification effect by microorganisms in the water, ® purification effect by dissolved oxygen contained in water, (D natural water purification caused by the cut in effect of matter that occurs due to the law of relative density, © natural water purification effect by surface pressure effect which occurs because of the law of gravity, ® natural water pu¬ rification by the capillary phenomenon, and finally (D natural water purification effect by the rising up of pollutants caused by osmotic pressure effect. Along with the above eight effects, there are some other effects that contribute to the natural purification of water as well. As water passes between each of the aeration-causing water gates (10) (20), whirlpools are incurred. Due to the whirlpool, pollutants are naturally separated and clean water molecules bond together. This is the self purification effect. Also, as the aeration effect occurs, pollutants rise to the top of the water. Then because of the division effect which divides the water molecules into layers according to their relative density, a difference of speed occurs in the flow of waters according to relative density. Therefore, due to the difference in flow speed, purification effect of the polluted river takes place in a more aggressive manner. [73] However, in the case each aeration-causing water gate (10) (20) is constructed in the above described manner so that it automatically opens according to water pressure, a more aggressive method is needed so that the opening or the opening pattern of each aeration-causing water gate (10) (20) could be controlled according to the pollution level of the water reservoir. For a more aggressive method, a motor power transmitting system (40) is connected to each of the secondary aeration-causing water gates. The secondary gates are fixed upon a hinge on the upper part of the main aeration-causing water gate (10). Then a central control system (50) that controls each of the motor power transmitting system is constructed. This control system is constructed in a manner so that it controls the closing, opening and patterns of each aeration-causing water gate (10 (20). After checking the pollution level of the water reservoir, if the pollution level is deemed to be high, then the main aeration-causing water gate (10) or the many secondary aeration-causing water gates (20) can be controlled to open in an angle the controller deems fit. Then each of the aeration-causing water gates could be set to open at different angles. Because this is possible, after the pollution level of the water reservoir has been measure, the opening angle of the water gates can auto¬ matically be controlled in accordance with the data obtained. Also, depending on the pollution level of the water reservoir, each of the aeration-causing water gates (10) (20) can be set to open at a large angle for a certain period of time and to open at a small angle for another certain period of time. In this way, even automatic time control is possible. So, the polluted river could be purified in a shorter period of time using this aggressive method. [74] Also, although the motor power transmitting system (40) that is applied in the present invention is not clearly specified, gears, cylinders, or rope controls can be used as the means for opening and closing the aeration-causing water gate. In addition, a power control board that either automatically or manually controls the power supplied to the means of closing and opening the water gate is needed. For the power to be supplied, power system that uses solar energy could be used. Or a hydroelectric generating system could be used by making use of the water that is discharged. In this way, the system could be constructed so that it can supply its own power. [75] The following is the explanation of the construction of the second working example of the present invention. It is shown in Figure 3. [76] The direction of the water discharge in the two sides of the river embankment is blocked and the aeration-causing water gate is constructed. The center of revolution of the aeration-causing water gate (30) is located on the upper part of the gate. In order for it to slant towards the direction of the water discharge, aeration-causing water gates (30) of multiple stages are installed between the walls (1) of the embankments. Then, when water is discharged from the water reservoir, the system is constructed in a way so that whirlpools are incurred between each of the aeration-causing water gates (30). With this structure, the aeration-causing water gates are opened due to water pressure and whirlpools are incurred between each of the aeration-causing water gates (30). During the process, oxygen in the air is naturally supplied into the water. Not only does the water come to life, but the pollutants also rise to the top. In the process of the incurrence of whirlpools because of water crashing against the aeration-causing water gates (30), pollutants are separated from the water molecules. The water molecules bond with each other and self-purification takes place. Then, according to the relative density of the matters contained in the waters, the clean waters located on the bottom layers flow out at a faster speed. And polluted waters with lower relative density are pushed to the top layer because of the push effect of matter. As this process is repeated, water becomes purified. [77] Also, for this structure, a motor power transmitting system (40) could be connected to each of the aeration-causing water gates as shown in Figure 4. Then a central control system (50) that controls each of the motor power transmitting system could be constructed. This control system could be constructed in a manner so that it controls the closing, opening and patterns of each aeration-causing water gate (10 (20) according to the pollution level of the reservoir. Then, a more aggressive purification of water could take place. [78] Polluted waters can be purified by natural means with the installation of an aeration-causing water gate of the second working example. The steps in which the pu¬ rification takes place shall be explained. [79] First, in order to discharge the water stored in the interiors of the first stage aeration-causing water gate, the lower part of the first stage aeration-causing water gate is slightly opened. Then water is filled up to the upper part of the inside of the second- stage aeration-causing water gate. At this time, if the lower part of the second stage aeration-causing water gate is slightly opened, then the inside of the third stage aeration-causing water gate is filled with water up to its upper part. At this stage, if the lower part of the third stage aeration-causing water gate is slightly opened, then the first, second, and third stage aeration-causing water gates are all filled with water up to their upper parts, and a constant amount of water is discharged. At this time, in the exterior parts of each of the multiple-staged aeration-causing water gates (30), aeration-causing materials are attached. Water molecules collide with those materials and whirlpools occur. Then, because of the whirlpools, pollutants which were bonded within the structure of the water molecules are separated and the separation effect of matter takes place. Then the polluted river becomes naturally purified. [80] Such effects as explained above also occur when the first working example is installed. And so the polluted river is purified by natural means. [81] Also, the second working example can be constructed by using the principles and structures illustrated in the first working example. Therefore, such changes are also subject under the patent rights of the present invention. [82] In addition, a constant distance can be put between the installations of each aeration-causing water gate in order to construct a purification system of multiple- staged discharge system. Therefore, such changes in design are also subject under the patent rights of the present invention. [83] All engineering works according to the aeration-causing purification system of the present invention are also subject under the patent rights of the present invention. Mode for the Invention [84] The natural water purification method of the present invention should be installed along the whole length of the river with a consistent distance between the installations. Then aeration-causing water gates are installed along the whole width of the river so that the functions of the present invention may be displayed to its maximum capacity. [85] However, in order to install aeration-causing water gates having rigid plate-like elements along the whole width of the river, the size of the aeration-causing water gate has to be constructed to be large and so this large size could rather be an obstacle that interferes with the drainage of the river. [86] In order to solve this problem, the aeration-causing water gates can be divided into several parts and installed in a way to block the river in several places. [87] Also, for the rubber dam which is constructed to block one whole section of the whole river, a discharge path for the lower layer waters can be made. The path would be constructed in the whole lower part of the rubber dam at a set height and in a straight line. Then, by using this discharge path, a multiple stage reservoir device could be constructed injunction with the rubber dam which would purify the polluted river by natural means. Since such a device would make use of the principles suggested by the present invention, it is under the patent rights of the present invention. [88] Also, any other devices such as the siphon tunnel or the conductive type water gate can be changed in a way so that they can make use of the principles displayed in the present invention. Therefore, any such structural changes are all subject to the patent rights of the present invention. Industrial Applicability [89] Today's rivers are getting polluted all the more by the day. Then, judging by the present state of rivers, the possibilities for the application of the present invention are limitless. [90] 70% of the earth's crust is formed of water and 30 % of land. Ecological problems that arise from water pollution are on a serious level. [91] Of those problems, in Africa, rapid desertification is taking place because of lack of water. And because of desertification, food production is impossible and so the population that faces starvation is on the increase. The number of deaths due to starvation is also increasing. Also, the speed of the desertification process of the inlands of Central Asia as well as Southwest Asia is increasing by the day. [92] In addition, because of the lack of water, water pollution is getting worse and oc¬ currences of diseases due to water pollution are on the increase as well. If water is stored by using the water purification method suggested in the present invention, then water can be used in plentiful amounts. At the same time, polluted rivers can be purified and brought back to life by natural means. Then, the present invention will play a significant role in changing the dry lands of Africa and inland Asia into fertile soil on which plants could grow on.