The Yellow River, the second longest river in China, flows through arid and semi-arid areas, providing valuable water resources for northwest and north China, and is an important source of life in northern China. The Yellow River basin has serious erosion, unstable riverbed, serious water pollution and fragile ecological environment. The Yellow River Conservancy Committee put forward the slogan of "maintaining the healthy life of the Yellow River", which turned the management of the Yellow River into multi-objective management. Based on the experience and lessons of river regulation at home and abroad, the author puts forward the following views on the comprehensive regulation of the Yellow River.

1. Controlling the undercut of the channel is the basis of controlling erosion.

The Yellow River flows through the loess plateau with the most serious soil erosion in the world. In the past, about 65.438+600 million tons of sediment entered the downstream every year, and about 400 million tons of sediment was deposited on the riverbed, which posed a great threat to people's lives and property on both sides of the lower Yellow River. We usually call gully erosion a form of erosion in which soil and parent rock are strongly eroded by slope runoff and cut into the ground to form large gullies. Gully erosion is the inducement of rill erosion and slope erosion. Trench undercutting makes bank slopes and branches steep, and rill erosion and slope erosion intensify, so controlling trench undercutting is the basis of erosion control. Erosion leads to the loss of nutrients in the soil and makes the land barren. At the same time, the nutrients carried by the sediment entering the Yellow River make the water quality of rivers and lakes eutrophic.

The fundamental way to control erosion is to control gully cutting and gully head rising, which can be controlled jointly by hydraulic engineering and bioengineering. Water conservancy project mainly refers to the construction of warping dams to intercept the sediment generated by scouring in the upper reaches of the Yellow River, so that it can be deposited in the river course, raise the river bed and reduce the slope, thus achieving the purpose of stabilizing the river course. In recent years, the construction of warping dams on the Loess Plateau has played an important role in blocking sand and controlling channel erosion. Bioengineering refers to planting vegetation that can effectively control erosion in the river or on the slopes on both sides of the river to protect the river and slope and prevent erosion and erosion. The research shows that restoring the vegetation coverage of slope to 70% can reduce the sediment yield of gully erosion by more than 75%. The key to controlling erosion by bioengineering lies in selecting suitable species. If species are selected properly, it can not only control erosion, but also increase biodiversity.

From 65438 to 0986, Qian put forward a scientific proposal to speed up the management of the loess plateau by developing seabuckthorn resources as a breakthrough, so that seabuckthorn shrubs could be planted in a large area on the loess plateau. Seabuckthorn, also known as Salix psammophila and Acacia angustifolia, belongs to Elaeagnus family and is a plant with good biological and ecological characteristics, strong adaptability, developed root system and strong germination ability. Population diffusion can be achieved by clonal growth, and the fitness of base plants and the survival probability of ramets can be improved by physiological integration and feeding behavior. Hippophae rhamnoides root system has high nitrogen fixation ability, which is of great significance to increase soil organic matter and nitrogen content, improve soil structure and improve forest productivity. It is found that planting Hippophae rhamnoides can effectively fix sand and store water, promote the growth of other local species, improve biodiversity and have good ecological effects.

Second, increasing resistance and slowing down is an important measure to stabilize river regime.

Stable river regime is very important for river health, and reducing flow is an important measure to stabilize river regime. Reducing the flow velocity mainly depends on the resistance structure of the river bed. Curved rivers, pebbles in rivers and vegetation on beaches are all part of the river bed resistance structure. These resistance structures can reduce the flow velocity, prevent river erosion and stabilize the river regime. At present, some river regulation projects have destroyed the resistance structure of river bed and caused many problems. From the point of view of comprehensive river management, cutting and straightening rivers, removing obstacles and reducing roughness in beach and channelization projects are not conducive to the health of rivers. Of course, reducing the flow velocity will lead to sediment deposition, so the resistance increase and deceleration should be carried out from top to bottom. On the whole, increasing resistance and slowing down fundamentally reduces the power of sediment erosion and movement, reduces the evolution rate of river bed, and makes the river regime gradually stable.

It is the nature of the river to bend, and it is against the nature of the river to turn the winding river into a straight river. Straight and concentrated water flow energy will cause river scouring and river bank erosion, which will lead to river instability, destroy aquatic habitats and affect the survival of aquatic organisms. Beach vegetation can reduce the flood velocity and prolong the flood advance time. Many scholars have studied the mechanism of beach vegetation affecting the hydraulic characteristics and geomorphological characteristics of rivers. The beach vegetation maintains the stability of river topography by increasing resistance and reducing the nearshore velocity, and increases the stability of river bank through its roots, thus accelerating the siltation of beach and river bank. Channelization of rivers will have adverse effects on river landforms and ecology. Hardening the riverbank with concrete has changed the original nature of the river. The roughness of smooth river bank is much less than that of natural river bank, which leads to the increase of nearshore velocity and threatens the safety of river bank and dike. It has been recognized that smooth river banks are not conducive to flood control safety. In some places, in order to control the nearshore velocity, large stones are embedded in the smooth revetment to increase the roughness of the river bank.

Reducing the flow velocity is not only beneficial to stabilizing the river regime, but also beneficial to the river ecology. Through the study of river biological community, it is found that when the flow velocity in the river is less than 2 meters per second, it is most conducive to the survival of aquatic organisms. Most aquatic animals and plants live in low-speed waters. Fitness index SI is the suitability of physical and chemical conditions of habitat for biological survival and reproduction. SI= 1 and SI=0 represent the best and worst living conditions respectively. The study of 36 species of fish shows that for adult fish, about 55% of them are most suitable for living in still water, and 97% are most unsuitable for living in water with a flow rate of more than 3 meters per second. Most fish lay eggs at a higher speed, while young fish need a lower speed. However, when the flow velocity is greater than 3m/s, the fitness index of all fish, whether adult or juvenile, drops to zero, while the fitness index of spawning, hatching and fry drops below 1.

Third, the construction of Tonghe Lake wetland is a chain to improve the ecology of the Yellow River.

Rivers are carriers of life and provide habitats for various aquatic organisms. At present, the Yellow River is in a state of serious pollution, more than 60% of its water is undrinkable, and its ecology has been seriously damaged. In addition, the bed of the Yellow River is fine sand, and the aquatic species and biomass of the Yellow River are much less than those of the Yangtze River. The author once led a research team to the lower reaches of the Yellow River and the Yellow River Delta for field ecological investigation, and collected benthic samples from the riverbed and wetlands of the Yellow River. Through analysis, it is found that only a few benthos live in rivers, while more species live in wetlands.

Tonghe Lake wetland plays an extremely important role in river ecology. In the water system, Tonghe Lake and the main tributaries of the river constitute a complete river and lake complex ecosystem. As different types of ecological units, rivers and lakes have their own ecological functions. Studies have found that many fish lay eggs in rivers and grow up in lakes. The relationship between Tonghe Lake system is beneficial to the survival and development of benthic invertebrates and fish. The running water environment of rivers has high dissolved oxygen, but the nutrients and bait organisms are poor; Tonghe Lake has high primary productivity, which supports all links of water food web. Conversely, lake ecology also depends on rivers. Therefore, maintaining the connectivity between rivers and lakes is very important for ecology. Studies have shown that the biodiversity of isolated lakes has decreased. Take the Yangtze River as an example. In the past 50 years, many lakes in the Yangtze River have gradually become smaller and isolated. In the isolated lake, the species of benthos decreased from 46 to 30, and the species of fish decreased from 80 to 50. One principle of ecological management is to maintain a high degree of connectivity between rivers and lakes. The construction of the Yellow River Tonghe Lake can significantly improve the ecology. For example, the main stream of Xiaobei, the floodplain of the second suspended river in Henan section, Dongping Lake, the flood detention area in the north exhibition and the flood detention area in the south exhibition can all build Tonghe Ecological Lake.

Another measure to improve the ecology is to increase the water surface area. Increasing the surface area can provide more habitats for aquatic organisms. From this point of view, building reservoirs and dams is beneficial to ecology. Although the construction of reservoirs and dams has isolated habitats and threatened some migratory fish, the increase of habitats has promoted the improvement of ecology.

Aquatic vegetation plays an important role in river ecosystem. Aquatic vegetation can provide benthic animals and fish with bait and a place to rest and lay eggs, and can absorb the organic matter in the river to achieve the purpose of purifying the river. Juma River in the suburbs of Beijing is a river with well-developed aquatic vegetation. Residents along the river use it as domestic water. The water discharged back into the river is domestic sewage containing a lot of organic matter, which is constantly absorbed by the vegetation in the river. After a certain distance of purification, the river becomes very clear. In the Yellow River regulation, aquatic vegetation can be planted in the conditional reach to purify the water quality.

Introduce suitable aquatic plants, such as submerged plants (such as Carex, black algae, POTAMOGETON, etc.), emergent plants (such as water wax, reed, etc.) and floating plants (such as lotus, Polygonum cuspidatum, duckweed, etc.) into Tonghe wetland and lake to construct benthic communities necessary for the life of the Yellow River and create and maintain a complete aquatic ecosystem of the Yellow River. The ecological restoration of water body should consider the restoration of the whole biological chain. For example, after the submerged vegetation is restored, it is necessary to consider both the maintainer of submerged vegetation and the garbage cleaner, that is, aquatic insects, snails and shellfish, and then release fish and shrimp.

4. Controlling point source pollution is the key to solve the pollution problem.

In recent years, the Yellow River has been seriously short of water and its pollution has intensified. According to the monitoring statistics of 200 1, the over-standard rates of phosphorus and ammonia nitrogen in the middle and lower reaches of the Yellow River are above 90% and 50% respectively. At present, the pollution of the Yellow River has both point source pollution and non-point source pollution. However, point source pollution can be controlled by sewage treatment and discharge, while non-point source pollution is difficult to collect and treat. Non-point source pollution is mainly nutrients that aquatic animals and plants can absorb or degrade; Point source pollution contains many toxic substances, which often kill some vertebrates and invertebrates and even vegetation, greatly reducing the purification capacity of rivers. Many examples show that after industrial sewage discharges kill higher organisms, some bacteria and algae can multiply, causing rivers to stink. Therefore, controlling point source pollution is the key to improve the water quality of the Yellow River. Previous studies show that if point source pollution is fully controlled, the surface water quality of rivers, lakes and reservoirs can be significantly improved.

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