The status and development ideas of check dam construction in the Loess Plateau area

1. Current status of development and construction of check dams in the Loess Plateau region

Check dams are a type of project created by the people in the Loess Plateau region of the Yellow River Basin in their long-term struggle against soil erosion. This is an effective water and soil conservation engineering measure that can not only intercept sediment, conserve water and soil, reduce yellow sediment, and improve the ecological environment, but also silt land for farmland, increase grain production, and develop regional economy. The earliest check dams were naturally formed, and recorded artificial dam construction began during the Wanli period of the Ming Dynasty, with a development history of more than 400 years. In 1945, the Yellow River Water Conservancy Commission built a check dam in Jingyu Valley, Xi'an. This was the first check dam built in the Loess Plateau. After the founding of the People's Republic of China, the construction of check dams in the Loess Plateau has developed rapidly through the review, demonstration and promotion of the water conservancy and water conservation departments. It has generally gone through four stages of development: experimental demonstration in the 1950s, promotion and popularization in the 1960s, development and construction in the 1970s, and the improvement and improvement of the dam system construction stage since the mid-1980s. The construction of check dams has evolved from focused trials to comprehensive development, from farmers taking the lead in building dams to government organizations and funding construction, from decentralization to small watersheds as units and construction of dam systems, from lack of planning and design to continuous improvement of standardization of preliminary work. Construction, from attaching great importance to construction to paying equal attention to construction and management, has achieved remarkable results. According to statistics, more than 110,000 large, medium and small check dams have been built in the Loess Plateau area, forming more than 300,000 hm2 of dam area, accumulating more than 21 billion silt, and reducing the annual sediment load of the Yellow River by 300 million.

2. The status and role of check dam construction in the Loess Plateau

Decades of practice have fully proved that the construction of check dams plays an important role in intercepting sediment, storing floods, and reducing erosion and solidifying water. It has produced significant ecological, social and economic benefits in terms of ditching, increasing grain production, and improving the ecological environment. It plays an irreplaceable role in soil and water loss control and ecological environment construction in the Loess Plateau.

1 Check dam is a key measure to intercept and reduce sediment

It is mainly manifested in three aspects: sediment interception, erosion reduction and flood detention. In terms of retaining mud, the check dam can not only retain the sediment produced in the channel itself, but also retain the sediment that flows into the channel from the slope. In terms of erosion reduction, after the sedimentation dam project is silted, it raises the erosion base level, which has the effect of preventing the expansion of the ditch bank, the undercutting of the ditch bottom and the advancement of the ditch head, and reduces the ditch erosion. In terms of flood detention and sediment reduction, it mainly intercepts floods and reduces channel erosion downstream of the dam, thereby reducing sediment input downstream.

According to the calculations of the Xifeng Soil and Water Conservation Station of the Yellow River Water Conservancy Commission on the three sedimentation dams in the Nanxiaohegou Basin, the channel ratio dropped from 11% to 15‰ before damming to 0.5% to 1 after sedimentation. ‰. According to a survey of more than 1,000 check dams in Suide, Zizhou, Jingbian and Hengshan counties in northern Shaanxi, it was found that 59,000 m3 of mud was retained per hectare of dam land, and the mud retention effect was very significant. Based on the analysis of various soil and water conservation measures in reducing the amount of sediment entering the Yellow River in the Hekou Town-Longmen section of the Yellow River where check dams are most concentrated, in the 27 years from 1970 to 1996, the amount of sediment reduction by channel dam projects accounted for the total amount of water conservancy and soil and water conservation measures. 59% of the sand reduction, especially in the 1970s, the dam system accounted for 76.7% of the total sand reduction.

This shows that the channel dam system project is a key measure to achieve rapid sediment reduction in the Yellow River, reduce the sedimentation of coarse sand in the lower reaches of the Yellow River, and prevent the Yellow River bed from raising. It has the effect of controlling sediment in small watersheds. Absolute control over sex.

2 The construction of check dams plays a prominent role in agricultural production in the Loess Plateau area

1. Increase the area of ??cultivated land and turn barren gullies into fertile farmland

Due to severe water and soil erosion, the Loess Plateau area has been cut into fragments with thousands of ravines. The gully density is generally 1 to 4km/km2. The dam system is constructed in the ditch, and the water and soil resources originally washed away by floods are retained in the ditch and fully utilized on site, so that the barren and uneven ditches of various sizes are silted up into fertile farmland, and the cultivated land area in the water and soil erosion area is increased. The dam land formed by a dam or a dam system ranges from several hectares to hundreds of hectares and becomes a small plain in the ravine. Especially in severely drained areas with many people and little land, damming and silting the land has become a very important way to increase basic farmland. Table 2 lists the siltation survey of typical channels at the Suide Water Conservation Station in Huangwei.

2． The soil in the dam area is fertile and farming is convenient, which increases the grain yield. Since the dam area retains topsoil lost from the slopes of small watersheds, containing a large amount of livestock manure, litter, etc., the soil is fertile; the groundwater level in the dam area is high, and the soil is fertile. It has sufficient water, good moisture content, and is resistant to drought; the dam land is flat and wide, making farming easy. According to calculations, the soil moisture content in general dam fields is 1.5 times higher than that of sloping farmland and 1 times higher than that of terraced fields; the nitrogen, phosphorus, potassium, and organic matter contents per unit soil are 1.2, 2.0, 5.2, and 1.3 times higher than those of sloping fields respectively. Table 3 shows the comparative data of soil water and fertilizer content in different land types measured at Suide Water Conservation Station. Because the dam land has good water and fertilizer conditions, the yield is higher compared with other land types. According to statistics, the unit yield of dam land is generally 5000kg/hm2, and some are as high as 8000kg/hm2, which is 4 to 6 times, or even more than 10 times that of sloping farmland, and 2 to 3 times that of terraced fields. It can be seen from Table 4 that although the area of ??dam land accounts for a small proportion of the total grain field area, the grain output of dam land accounts for a large proportion, indicating that dam land agriculture plays a decisive role in the agriculture of the Loess Plateau region.

3． The construction of check dams can promote the conversion of farmland to forest and grassland and the adjustment of agricultural structure. The work of returning farmland to forest and grassland is a major decision taken by the Party Central Committee and the State Council at the beginning of the new century to implement the sustainable development strategy. It will definitely promote the ecological environment of our country. Overall development of construction and conservation undertakings. The construction of check dams has increased high-quality farmland resources for farmers in mountainous areas, achieving both ecological construction and enriching people's income. The improvement of the ecological environment and rural economic development complement each other. It can fundamentally relieve the masses' worries, promote the return of farmland to forests and grassland, and promote the return of farmland to forests and grasslands. The strategic adjustment of the agricultural structure and even the industrial structure will play an important role in recreating the northwest region with beautiful mountains and rivers. In Qiugou, Xuecha Township, Wuqi County, Shaanxi Province, since the average per capita farmland has reached 2 acres, the people are very receptive to returning farmland to forest. In the winter of 2000, 32hm2 of farmland was returned to forest at one time, and the per capita farmland was 0.27hm2. There are many such examples, which are enough to illustrate the role of check dam construction in returning farmland to forest and adjusting the agricultural structure in the Loess Plateau.

4． Replacing roads with dams improves traffic conditions and promotes local economic development. After the check dam is completed, the top of the dam becomes a bridge connecting the two sides of the ravine, which improves local rural traffic conditions, facilitates the production and living conditions of the people, and promotes material and cultural exchanges. and the development of commodity economy. According to statistics, about 20% of the backbone ditch control projects have become the main local traffic roads. After the completion of the Huacha small watershed dam system in Dingxi County, 50km of village roads were connected, and cars could be connected between villages and groups in the entire basin. 8 agricultural and sideline product processing points and commodity sales points were set up along the way to promote the development of local economy.

5． Flood prevention and disaster reduction, protecting downstream production safety. Although check dams will be damaged to varying degrees when encountering excessive rainstorms and floods, for channel dam system projects, especially dam systems that are relatively stable or controlled by backbone dams, in It can still play a huge role in detaining floods and mitigating downstream disasters. According to surveys, heavy rains and floods occurred frequently in the middle reaches of the Yellow River during the flood season in 1994, but none of the backbone dams built suffered flood disasters. In many small watersheds, many small and medium-sized check dams were effectively protected by backbone dams, and not only did no floods occur In the year of disaster, we achieved a bumper harvest. In the Mazhuang River Basin of Yan'an City, five backbone dams have been built since 1986 to effectively protect 23 check dams in the basin. The total output of only 80hm2 of dam land protected reached 500,000 kg.

6． To improve the utilization rate of water resources and solve the problem of water consumption for rural production and living, the first is to increase the water flowing in long channels. According to observations of the Jiuyuangou watershed by the Suide Water Conservation Station, the average regular water flow in the ditch was 28L/s from 1954 to 1964, and 36L/s from 1964 to 1968, an increase of 28.6; by 1965 to 1988, the average flow reached 65L/s, an increase of 1.3 times compared with the period from 1954 to 1964. The second is to regulate water resources to ensure full and rational utilization of water resources. Precipitation in the Loess Plateau is unevenly distributed throughout the year. 70% to 80% of precipitation is concentrated in the flood season from July to September. However, from May to June when crops need water for growth, there is often drought and little rain, and there is no water available. However, the dam system Excess precipitation during the flood season is captured and stored for reasonable adjustment and use. The third is to use the early water storage in the check dam to develop aquaculture and irrigation.

The Daohui ditch dam system in Dingxi County, Gansu Province uses the early water storage in the backbone dam to supplement 60hm2 of water for the Zhonghe Irrigation District every year, develop 55hm2 of water land, and release 300,000 fish fry. The fourth is to solve rural domestic water needs. The Chuanzhanggou Basin in Inner Mongolia has poor groundwater resources. Every spring there is drought and little rain. The rivers dry up and drinking water is very difficult. This has long restricted the development of agriculture and animal husbandry and the improvement of people's living standards. Through the construction of channel dam system projects, six villages in the basin have solved drinking water problems by using water stored in the early stage of the project.

7. It has significant economic benefits and promotes rural economic development. Due to the high and stable yield of the ditch dam, it creates conditions for the development of efficient agriculture and agricultural structural adjustment, increases farmers' income, and promotes the development of the rural economy. In the Abuhai River Basin of Ordos City, Inner Mongolia, 12 backbone dams and 35 small and medium-sized check dams have been built. A comprehensive watershed management pattern focusing on dam system construction has initially been formed, which has promoted the development of special breeding and tourism. The total agricultural output value has been 5.32 million yuan increased to 7.68 million yuan, and the per capita income reached 2,430 yuan. 3. The future development ideas for the construction of check dams in the Loess Plateau. Based on the actual conditions of the Loess Plateau and the needs of soil and water conservation, ecological construction and coordinated economic and social development, the overall development ideas for the construction of check dams in the future are: based on the spirit of the 16th National Congress of the Communist Party of China and the " Guided by the important thinking of "Three Represents", through the construction of large-scale check dams, sand and water storage, effective use of water and soil resources, the construction of basic farmland with high and stable yields, consolidating the results of returning farmland to forest and grassland, and increasing agricultural production in the Loess Plateau region , increase farmers’ income and create conditions for rural economic development. Give full play to the ecological self-repair ability, promote large-area vegetation restoration and ecological environment improvement, support the sustainable development of the economy and society with a good ecological environment, and provide support and guarantee for the comprehensive construction of a well-off society.