.

I think the dam needs to be repaired, and more leaky dams need to be repaired."

"How is this possible for a leaky dam? If the dam can be built into a leaky dam, then I can build it!"

Zhao Gang didn't expect that Huang Wanli, an honest man, would have such humor. It seems that people should not behave like this. However, after listening to Huang Wanli's explanation, Zhao Gang learned that there was really something called a leaking dam.

"A water leakage reservoir is a water conservancy project between an ordinary reservoir and a silt dam. It promotes the conversion of ground water to groundwater to achieve various goals such as flood control and disaster reduction, increasing the supply of water and soil resources, and improving the ecological environment. This kind of dam has little quality requirements and little environmental damage. I personally suggest that leaky reservoirs can be built according to local conditions."

Seeing that Zhao Gang still didn't understand, Huang Wanli continued:

"In fact, water leakage is a taboo in reservoir construction. In order to prevent water leakage, we have to adopt complex engineering measures, such as adding a concrete anti-seepage wall of 70m deep under the Yangtze River dam to block leakage in the cover layer. But under certain conditions, water leakage may also be a good thing.

Last year, I went to Zizhou County, Shaanxi Province and saw a wetland formed by a landslide. The natural dam at its blockage was about 60m high, and nearly 1,000 mu of silt land behind the dam. After heavy rain, there was a lot of water in the dam, but it leaked within two or three days, which did not affect the growth of crops in the dam.

This naturally formed water leakage reservoir plays at least two important roles, namely silt and flood retention. It gives me an inspiration: Can water leakage reservoir be built manually to achieve the goal of promoting profit and eliminating harm and increasing the total water supply? If possible, how should such a reservoir be planned, designed and built? Later, I thought about it for a long time and finally got some ideas.

When it came to the excitement, Huang Wanli took off his clothes and formed a half circle, and found many pens to put them on the paper.

"You see, this is a local loess highland, which is a lot on the Loess Plateau. Then we show it in this position." Huang Wanli finished speaking, putting his pen in the gap and putting it on the market for dams. The overall goal of building a leaky reservoir is to store water and soil resources as much as possible on the land, reducing the total amount of water and sand into the sea, thereby increasing the total supply of water resources. Compared with ordinary reservoirs, leaky reservoirs have the following characteristics:

The first is to use underground space to store water, and there is no need to permanently occupy land;

The second one avoids water loss caused by water surface evaporation in ordinary reservoirs;

The third one can block water and soil and fertilizer, which can silt and create excellent farmland;

The fourth is to reduce soil erosion and siltation of the lower river reservoirs;

The fifth one supplements groundwater to mitigate ground subsidence and seawater invasion disasters caused by the drop in groundwater levels.

If you see that, we don’t have to build more than 40 dams on the Yellow River, and we can achieve the same purpose, or even do better than that. The wages are saved a lot. I have calculated that under the same warehouse capacity, the construction cost of tax-eliminated dams is less than 1/20 of that of a regular dam. This money can be saved. There are many things we can do."

Zhao Gang nodded. The dissatisfaction just now had disappeared. This new type of ground dam was just like a tailor-made for people in the Northwest region. In this way, the amount of water that can be used for irrigation in the Three Norths can be increased by at least half. The Chinese canal plan can further reduce the scale. Zhao Gang couldn't help but regret not having contacted Huang Wanli earlier. If that were the case, how much financial resources could be saved! Governing a big country is like cooking a small freshman, and this sentence is true.

"Is this a silt dam? Once the Yellow River floods, will this dam come in handy?"

What Zhao Gang is most concerned about is the flood control issue of flooding in the Yellow River. This is not that he is not interested in people's livelihood, but because he is sitting in this seat. It is his main responsibility to consider more important matters and prevent people from being hurt.

"This kind of water leakage reservoir is different from a silt dam. First of all, in terms of flood control, water leakage reservoirs can also play a temporary flood blocking role like ordinary reservoirs. Of course, the water it intercepts cannot be directly used for power generation, irrigation, urban water supply, etc., but can only be used indirectly through extraction.

Therefore, this kind of water leakage reservoir has another advantage compared to a silt dam, which can block water. The latter often only blocks mud, not water, and cannot retain floods. Moreover, silt dams are always built in ravines, while water leakage reservoirs can also be built in low-lying plains. In this way, when the flood comes, this part can effectively reduce flood peaks.

In short, the basic function of a leaky reservoir is to convert surface water into groundwater, so it can be defined as "a water conservancy project that promotes the conversion of surface water to groundwater to increase the supply of water and soil resources." You also know that the Nile River floods regularly, not only did not cause major disasters, but instead formed the Nile Corridor and nurtured the Euphrates civilization. This is because they know how to take advantage of the situation rather than copying it. "

Zhao Gang stood up and turned his gaze to the map of China on the wall. The vast 30 million square kilometers of land was like a huge shuttle. In the center of the shuttle was the yellow Three Norths. This was once the birthplace of the Yellow River civilization. After thousands of years of development, it has become barren.

After a long time, Zhao Gang's voice came over, a little solemn:

"Minister Huang, it's no secret of being empty. What I want is a realistic plan, not your theory. How long does it take to come up with a plan that can be implemented."

Huang Wanli was overjoyed and thought for a while before answering:

"Three days, I need three days."

Three days later, the planning and design of the leaky reservoir was handed over to Zhao Gang, and the designer of the plan was forced to rest because of three days of sleeplessness. With excitement, Zhao Gang opened the cover and began to understand the planning of the leaky reservoir.

1. Terrain and geological conditions

There should be a strong permeable layer in the strata of the leaky reservoir, which is not buried deep, so as to transport the leaked water to the distance as soon as possible. Burying the permeable sand and pebbles layer too deep will undoubtedly increase the cost of the leaky well. In stone mountainous areas, riverbeds are often composed of sand and pebbles. If a dam is built on it, the undercurrent from the dam foundation will soon flow into the downstream river channel, and the goal of converting into groundwater cannot be achieved, so it is not advisable to build a leaky reservoir.

Therefore, the construction of leaky reservoirs is best carried out in the Loess Plateau area, where the water leakage performance is good. Moreover, the water is a vertical guide and there will be no return to the river. The terrain conditions of suitable water leakage reservoirs are the same as ordinary reservoirs in principle, that is, the valley leaky reservoir should be built in a valley with a small mouth and a large belly, while the plain leaky reservoir should be built in a depression on both sides of the river. In this way, the flood can be effectively intercepted when the flood arrives.

2. Hydrological meteorological conditions

Leaky reservoirs are suitable for building semi-arid areas with relatively concentrated summer rainfall, especially areas with excessive groundwater levels. These areas must meet the following four conditions: overall insufficient water resources; seasonal water resources are oversupply, which has to be discharged into the sea; large evaporation;

There is sufficient water storage space. Specifically, it is the Three Norths, including western North China, Henan and some areas of Shaanxi.

3. Layout of leaky reservoirs

Exit-controlled leak reservoirs can be arranged on small tributaries in mountainous areas. For tributaries with relatively large water volume, a cascade-stage storage leak reservoirs can be built. The leak reservoirs should be comprehensively planned with silt dams and ordinary reservoirs, and the local conditions are suitable for construction of which kind of projects.

In plain areas, leaky reservoirs can be arranged in a long-wild vine-shaped melon-shaped shape, that is, low-lying areas on both sides of the river. Unlike general flood retention areas, leaky reservoirs should be surrounded by dams to increase the depth of water storage, so as to achieve the purpose of storing as much water as possible within a small flooded area. Of course, leaky wells should also be arranged in the reservoir.

4. Library capacity design and operation control

It can only be designed according to the semi-blocking type. The storage capacity of a plain leaky reservoir should be determined based on the terrain conditions and the flooding loss. In principle, the top height of the reservoir embankment should be slightly lower than the top height of the river embankment so as to increase the storage capacity as much as possible. The operating mode of a leaky reservoir can be divided into two categories: multi-year water division type and annual water division type.

The former is to divert floods when encountering large floods, for example, at the frequency of 5 times; the latter is to divert water into the reservoir every year during the flood season to achieve the goal of reducing the amount of water entering the sea. Obviously, the latter operation method is to increase flood losses. Because the harvest is based on the two quarters of each year. The loss rate of 5 times is 10%, while the loss rate of 5 times is 50%. Of course, this is a rough estimate. In fact, the water level during the flood season will not be too high, and of course the range of the flood areas should be smaller.

A leaky reservoir can also retain part of the storage capacity for permanent water storage to meet the water needs of the reservoir area and surrounding areas.

This content of practice is just a general discussion. Zhao Gang looked at ten things at a glance and then flipped through it. The following is the most important content, divided into four points and discussed in detail. It seems that these things are not a day in Huang Wanli's mind. Therefore, they can be written in just three days.

There are not many main buildings in the leaky reservoir. Compared with ordinary dams, there is one more leaky well. The requirements for large dams can be said to be extremely low, far lower than the requirements of large dams, and only equivalent to the requirements of general small dams.

Water leakage reservoirs are mainly small and medium-sized projects and are generally built on the cover layer. Therefore, waterproof buildings should be mainly earth dams, and can generally be designed as homogeneous earth dams. Given the characteristics of water leakage reservoirs, their construction standards can be lowered.

First of all, there is no anti-seepage requirement. Even sand and pebbles can be used to build dams. Secondly, the water barrier time is short, generally no more than March. Infiltration lines are not easy to form in the homogeneous dam of clay soil, and there is no problem of sudden water level drop in the upstream. The filling density of the dam body and the requirements for the slope ratio of the dam can be reduced.

Therefore, the dam body can be filled with relatively fast and cheap directional blasting or hydraulic flushing method. When using the latter method, vacuum pumping can be used to accelerate the consolidation of the fill. However, in order to ensure the stability of the penetration, measures are still required to prevent pipe surges.

A leaky well is a key facility for a leaky reservoir, and it must ensure that it operates for a long time without being blocked. It is different from the drain wells set up in the earth dam to reduce the infiltration line. It must ensure that a single well has sufficient drainage capacity. The drainage volume and number of wells of a single well should be based on the water accumulation in the reservoir area within 100 to ensure that the flood loss of farmland is limited to autumn crops. The bottom of the well should be penetrated deep into the sand and pebbles layer, but how the water inlet should be set, whether its elevation changes with the reservoir water level or is fixed on a certain elevation, its design and layout method need to be further studied.

A water separation dam needs to be built between the plain water leakage reservoir and the river channel. However, unlike the water separation gate used in the conventional sense for the flood diversion area, the amount of water flowing into the leaking reservoir automatically penetrates into the ground and does not have to wait for the flood to recede into the river channel. Therefore, it only needs to be designed according to one-way flow. The simplest solution is to use a concrete rolling dam, which is connected with a rubber dam on it, and even uses self-cruciduous soil protons~.:. Effective.

If the mountainous water leakage reservoir cannot store all incoming water and must operate in a semi-storage manner due to the limitations of terrain and geological conditions, flood discharge facilities need to be arranged, such as dam top spillway or dam foundation flood discharge hole. Small projects can adopt the method of dam top spillway and geotextile protection. If medium-sized projects do not have conditions to build spillways on both sides of the shore, flood discharge holes should be considered for burying flood discharge holes on the dam foundation. If there is a soft soil layer on the dam foundation, in order to avoid settlement and breakage, it can be built using the pipe-pipe after the dam body is filled.

Later, Huang Wanli also wrote in detail how to transform the silted reservoir and make it a leaky reservoir.

For mountain reservoirs with severe siltation and basically lose their water storage function, if conditions permit, water leakage wells can be added to make them leaky reservoirs to make them leaky reservoirs to utilize the flooded land resources. If the plain flood retention area is not added to allow the flooding, the flooding loss will be great. If the low-lying land with relatively poor ridges is fenced and converted into a leaky reservoir, although the investment is greater, it can be used repeatedly with confidence, which may be cost-effective.

In addition, leaky reservoirs will gradually be silted like ordinary reservoirs, and some may eventually be silted and scrapped. Huang Wanli also studied this problem. In order to reduce silt and extend the service life of the reservoir, the following measures can be considered: Use the top pipe method to add sand drainage holes at the bottom of the dam. Use silt soil to increase the embankment or embankment to use the method of dam storage and increase the dam. In this way, the cost of one-time investment in the embankment project can be reduced. Manual dredging, and the excavated silt is used to improve farmland in surrounding areas.

After Zhao Gang finished reading it, he agreed with Huang Wanli's idea. For the northern semi-arid areas, there are only two ways to increase the supply of water resources: one is to divert water from other places, namely the Chinese canal project; the other is to base on local precipitation, that is, to store more and evaporate less.

Taking the area of ​​500mm annual precipitation as an example, if precipitation accounts for 60% during the flood season, and 10% of the precipitation (30mm) is stored underground, and the area reaches millions of square meters.} The total water volume of 30mm will reach more than 150 cubic kilometers, which shows the huge water storage capacity of underground reservoirs. Once promoted and opened, the water transfer volume of Chinese canals can be reduced by more than half.
Chapter completed!