Background Art Conventional underwater dam discharges water through an upper part of a water gate thereof, so that it causes water stored therein to be foul on the contrary.

Describing more specifically, when water is stored, contaminants contained in water is decomposed naturally by solar heat, and these decomposed contaminants are piled up near a lower part of the water storing device and become bottom materials or sludge as a molecular structure of them become heavy, that is a specific gravity of them become heavy.

Sludge is created by the accumulation of the contaminants, which are decomposed by the four major actions, the purifying action of solar heat, the purifying action of the circulation layer, the purifying action of the dissolved oxygen, and the

purifying action of the microorganism in water. Since the sludge once piled up photosynthesizes continuously before being dredged up, an accompanying contamination due to chemical reaction in the sludge occurs, and this is the major defect of the water gate which adopts an upper discharge manner.

Therefore, when the underwater dam is constructed using the upper discharge type water gate, the water contamination is generated more seriously due to the sludge accumulated at the lower part of the underwater dam.

In addition, conventional large-sized water storing device uses a construction method wherein a large dam blocking valley is built in order to store a large amount of water at the same time and discharge this stored water at appropriate time when needed, ruins of ancient time or a farmland located in low land is submerged when the dam water overflow, and due to vaporization of the stored water, the number of foggy day is increased and a respiratory disease breaks out frequently among residents around the dam.

Among the physical and chemical reaction decomposing contaminants in water, is the natural self-purification effect where oxygen contained in water decomposes contaminants naturally, and the secondary natural purification effect by oxygen and air of the circulation layer contacting with water. Since the natural purification action by dissolved oxygen and microorganisms has a good effect, it is used widely in a sewage treatment plant and this fact is known in academic field as well.

Disclosure of Invention When a multi-staged underwater dam is constructed using an automatic water gate of low discharge type in a method for improving a water quality naturally using a multi-staged water storing device according to the present invention, secondary

contamination does not occur since accumulated sludge which is created by an natural purification effect.

Since organic contaminants which is not purified in the first stage of the water storing devices could be purified again in the next stage of the water storing devices, a large amount of the organic contaminants is decomposed at low cost if the multi-staged water storing devices are constructed and a large amount of the water is stored therein.

That is, the present invention improves a quality of contained water without additional operation, and also uses the automatic water gate, which is fully opened by a cylinder rod operated by a water level detecting sensor and the water level increased naturally in a flood and rainfall, and then is closed by the cylinder rod operated automatically when the rainfall stops, so that the water storing devices could be operated smoothly.

Additionally, in the present invention, a large amount of water could be stored and the quality of the contaminated water could be purified by using the force of nature without the construction of a large dam.

The present invention is contemplated to solve the aforementioned problem, and it is an object of the present invention to provide the multi-staged water storing devices which uses the automatic water gate that is closed by an operation of a cylinder, the main driving unit mounted to an upper part of a supporter in order to initiate the water storing operation when a flow rate from an upper stream is decreased, and is opened by water pressure and buoyancy, simultaneous with the elimination of the pressure of the cylinder by the water level detecting sensor in order to discharge water when a flow rate from the upper stream is increased, so that a constant water level is maintained continuously, and thereby causes the quality of the contaminated water to be purified naturally by the

purification action of solar heat, circulation layer, and microorganism/dissolved oxygen in water, which decompose contaminants contained in water naturally.

That is, it is the main objection of the present invention to provide a system, in which a certain amount of water is stored in each multi-staged water storing device, and then this stored water is discharged to the amount flowed in through the lower part of the water storing device.

To accomplish the above object, the present invention provides a method for improving a water quality naturally using an underwater dam, which uses an automatic water gate of low discharge type such as a water gate for forming a fish way, an underwater dam in a river for securing water used for irrigation or industry, an automatic water gate for an irrigation canal, and a full automatic dam for making an amusement park in downtown, being characterized in that the multi-staged water storing devices are constructed along the water level of the entire river, and stores a certain amount of water so that the stored water is discharged to the amount flowed in from the upper stream of the river through the lower part of the water storing device.

Brief Description of Drawings The features and advantages of the present invention will be more described specifically in the following description of preferred embodiments of the invention with reference to the accompanying drawings wherein: FIG. 1 illustrates closed status of a multi-staged water storing device in the present invention; FIG. 2 is an enlarged view of the water storing device of FIG. 1; FIG. 3 illustrates opened status of a multi-staged water storing device in the

present invention; and FIG. 4 is an enlarged view of the water storing device of FIG. 3; and FIG. 5 illustrates another embodiment of the present invention.

Best Mode for Carrying Out the Invention Reference will now be made in detail to the embodiment of the present invention and examples of which are illustrated in the accompanying drawings. In explaining the present invention, the same names and reference numerals will be given to the same components, and explanations in the same will be omitted.

FIG. 1 illustrates closed status of a multi-staged water storing device in the present invention, and FIG. 2 is an enlarged view of the water storing device of FIG. 1; A reference numeral 1 indicates a multi-staged and low discharge type water storing device which is constructed to block the river across an entire width thereof along a water level of an upper and lower stream of a river, or at each point of 50%-70% or certain value of the stored water level.

The water storing device 1, as shown in FIG. 2 comprises a pair of wall 17 built at both sides of a canal with a predetermined distance, a supporter 14 fixed uprightly to inside of the wall 17, a water gate 11 which is a hollow rectangular plate having packing 12 at both lower sides, rotative shaft is provided to both sides of an upper end thereof so as to be coupled to an upper part of the supporter 14 by a hinge 16, and a lower end thereof is located between the walls 17 inclined toward the discharge side, a cylinder 15 which one end thereof and the other end are coupled rotatively to the supporter 14 and the water gate 11 respectively so that the water gate 11 is ascended and descended about the hinge 16, a gate frame 13 which is formed beneath the water gate 11 with being inclined

to both walls 17 and serves to reserve water together with the packing 12 in closing the water gate 11, and a sensor 18 which is mounted to stored water side of the wall 17 with certain height for detecting the water level of the stored water.

The above water storing device 1 may be installed to block continuously the entire canal or some part thereof which has the upper and lower stream generating difference in the water level, but it is preferable that the water storing device is installed at an end of the water level or the water storing device is installed overlapped to maintain a constant water level. Also, when the width of the river is wide considerably, a plurality of the water storing devices are installed along the width of the river and could store and discharge water by stages according to the quantity and pressure of water.

The method for improving the water quality naturally using the multi-staged water storing device described above will be explained as follows.

The length of the canal or river is considerably long, and thereby the length of dam constructed to protect this canal and river, and a residential area and farmland, is greatly long.

The present invention is to cause contaminated water to be purified naturally by constructing a multi-staged and low discharge type water storing device along a water level of an upper and lower stream of a river, or at a point of 60%-80% or middle value of the stored water level, using the dam.

FIG. 3 illustrates opened status of a multi-staged water storing device in the present invention, and FIG. 4 is an enlarged view of the water storing device of FIG. 3.

Firstly, describing the operating status of the water storing device 1 as shown in FIG. 4, since the water pressure is low when the store water level is low, the water storing device maintains the closed status by its self weight. And, as the water lever become high

gradually, the cylinder is operated by the signal of the water level detection sensor 18 set in predetermined height so that the lower part of the water gate 11 is opened and then the discharge of water is performed, and eventually it could be possible to store water of constant amount continuously.

The multi-staged water storing devices 1 are closed from the downstream by stages in storing water as shown in FIG. 3, and is opened from the upper stream where the water pressure is more higher, by stages in discharging water.

The World Health Organization (WHO) has announced after analyzing the component of contaminants in water, that about 2,000 components are contained in water, about 600 components among them are not edible, and it could not figure out which one among the rest 1,400 components is good or harmful for human.

Not referring to the theses and announcements of the academic field that solar heat decomposes naturally organic matters distributed in the surface of water, it is laiown to scholars who researches water that the natural improving effect of the water quality does not exist in a covered river that solar heat could not reach.

Considering such fact, it could be aware that organic contaminants are decomposed only by solar heat in stored water.

The organic contaminants are created from the vegetable, mineral, and animal oil which have the light specific weight, the livestock waste water and the like, positioned in the surface of water when mixed with water, and diluted with water when water flows.

These diluted organic contaminants are caught by the upper part of the automatic water gate when the automatic water gate discharges water through its lower part.

That is, the organic contaminants have the characteristics to be separated from water because of its molecular structure lighter that that of water. Due to this

characteristics, a certain amount of the separated organic contaminants are decomposed by the decomposition action by solar heat, the decomposition action by the friction effect of the circulation layer contacting with air, and the natural purification action by the microorganism and dissolved oxygen contained in water, during they remain near the upper part of automatic water gate 11 in the water storing device 1.

Water once purified by the natural self-purification action described above, becomes completely purified water, passing through the multi-staged water storing device.

The problem occurred in this water storing device performing the natural purification, is when the store water is discharged in case of a flood. However, if it is set in advance when the discharging or storing water is initiated according to the water level, the water gate operates automatically based on the set water level, so that the above problem is resolved.

Various water gates are applied to the present invention to obtain the effect described above.

Firstly, there are water gate operation methods in which the water gate is opened and closed by a driving device provided to both sides of the upper end in water gate, and the driving device is included in the water gate so that the stored water is discharged through the lower part of the water gate.

Further to these, there could be the method wherein the water gate is reversed automatically or manually when the stored water reaches to a certain water level.

In the method using reversible water gate, the driving device is mounted outside or inside of the water gate, or a plate member is attached to the water gate in order to use the siphon effect where lower water is pumped up to the upper part of the water gate due

to the capillary phenomenon.

Still another method illustrated in FIG. 5 will be explained as follows.

As illustrated, the method for improving water quality using the multi-staged water storing device could be possible by using a low discharge type rubber dam 20 in which a fish way 23 formed at a bottom of the canal is opened and closed by opening/closing means 22, so that the stored water could be discharged beneath a rubber dam body 21 in the middle of the canal.

Therefore, it would be apparent that the multi-staged water storing system and the method for improving the water quality using the same which are modified variously as described above, are included in the scope of the present invention, although the method for storing water or operating the water gate are changed.

Industrial Applicability The effect of the method for improving the water quality by the multi-staged water storing device according the present invention which is installed in order to store water and purify the contaminated water, is as follows.

A river has served as a canal to flow rainwater to downstream when it rains or a flood occurs up to now. However, in the present invention to solve this problem, since multi-staged water storing devices are constructed in the entire river using a water gate opened and closed automatically, and water stored or flowed in is discharged though a lower part of an automatic water gate of the multi-staged water storing device, the water quality is improved by the natural purification action of the stored water.

In addition, if a flood or a large amount of rainfall occurs, the water gates of the multi-staged water storing devices are opened and closed serially in a automatic manner,

so that an unexpected dangerous situation could be managed.

Further, when a flood occurs, the river has a problem that have the considerable amount of water directly since a fast flowing stream is formed in the river. However, when a full automatic dams, that is the multi-staged water storing device using the automatic water gate is installed along a level of the stored water or at each certain or middle point of the stored water level, using the method for improving naturally the water quality according to the present invention, a constant amount of the entire rainfall is stored continuously, although the heavy rainfall is occurred.

Since the multi-staged water storing device could store a large amount of water, water needed for various purposes is supplied appropriately, no matter how a drought prolongs.

Moreover, when a large amount of water is stored and at the same time water flowed in from the upper stream of the river is discharged gradually through the lower part of the automatic water gate, the quality of the contaminated water is improved by the natural purification effect of the water quality by solar heat irradiated to the stored water, the natural purification effect in the circulation layer by air and oxygen contacting with the stored water, that is the natural purification effect of the water quality by the mixture operation due to the friction of the waves, and the natural decomposition effect by the microorganism and dissolved oxygen contained in water.

That is, each time water passes through one of the water storing devices, the effect that the water quality is improved gradually exists, and the water quality is improved completely, passing through the all the water storing devices installed in multi- stage. Therefore, the natural improvement in the water quality could be achieved by using the multi-staged water storing device of the present invention.

Meanwhile, it would be apparent that the constructing methods of the multi- staged water storing device for installing a rubber dam so that water is discharged beneath the rubber dam, installing various water gates so that water is discharged by siphon effect, or using the water gate of which the lower part is opened and closed, are included in the scope of the present invention, though they are somewhat different each other.