Hengye Reservoir is located 2km east of Zhanhua County, Binzhou City, on the left bank of the main canal of Chaohe River, with a rectangular plane, which is the floodplain of the alluvial plain in the lower reaches of the Yellow River. The project area is short of fresh water resources, sparse surface vegetation and serious soil desertification, which belongs to the key control area of soil erosion. The strata in the project area are silty soil, silty clay and clay deposited by Quaternary Holocene alluvial deposits, and silty soil, silty clay and silty sand deposited by Quaternary Holocene marine deposits. There are many types of soil in this area, including fluvo-aquic soil and saline soil, and there are three subtypes of fluvo-aquic soil, saline fluvo-aquic soil and coastal fluvo-aquic soil. The main vegetation is plain vegetation. The plane of the project area is approximately rectangular, with the east-west length of1900m and the north-south width of1000m. The whole project covers an area of 220hm2.
Soil erosion is mainly wind erosion, and water erosion is slight. The reservoir site is now saline-alkali wasteland, with poor soil fertility and easy wind erosion. It belongs to moderate wind erosion control area, and the erosion modulus of water and soil loss is 2500 t/km2 * a, and the types of water and soil loss generated during the project construction are wind erosion and water erosion. At the initial stage of operation, the plant measures implemented in the project area are in the survival period, and the ability of wind prevention and soil fixation is poor, so there is also a certain degree of soil erosion.
2, soil erosion prevention and control scheme
According to the relevant provisions of Technical Specification for Soil and Water Conservation Scheme of Development and Construction Projects, the scope of responsibility for soil erosion prevention and control includes the project construction area and the directly affected area. The project construction area includes the permanent land acquisition scope and temporary land occupation scope of the construction unit; The directly affected area refers to the scope of direct harm caused by development and construction activities outside the project construction area. According to the layout and characteristics of the main project, the responsibility scope of soil erosion prevention and control is determined to be 59.25hm2. Based on the analysis of the influencing factors of soil erosion in the project area and the characteristics of soil erosion in this project, comprehensive prevention and control measures combining engineering measures, plant measures and temporary protection measures are adopted to scientifically prevent and control the original soil erosion and new soil erosion in the project area and improve the ecological environment around Hengye Reservoir.
Through analysis, after the completion of the project, we decided to focus on protecting the dam crest, dam slope, pumping station and embankment. During the construction period, temporary protective measures such as laying waste soil, shaping and loading soil in woven bags shall be taken for the temporary slag stacking area of the project, and the construction party shall be required to suspend earthwork construction when the wind speed is greater than or equal to level 5 wind; After the construction, the temporary land will be leveled, the original landform will be restored, and vegetation will be planted in the soil yard. In short, in the process of engineering construction, various measures are reasonably matched to give full play to its best benefits.
3. Specific measures
3. 1 dam crest and slope prevention measures
3. 1. 1 dam crest preventive measures
After the completion of the project, the dam will be newly built, the soil will be exposed, and the number of vehicles entering and leaving the dam top will increase. The strengthening of human activities will deepen the degree of soil erosion. In order to protect the ecological environment and prevent soil erosion caused by wind erosion on the dam crest, the dam crest was hardened in the main project design. Dam crest hardening includes mechanical rolling subgrade, spreading lime stabilized soil foundation, asphalt surface treatment and greening and beautification. During construction, after spreading lime stabilized soil base, cover it with woven bags filled with waste soil to prevent soil erosion caused by wind; After the construction, the soil of the laid woven bag should be removed and recycled to avoid the woven bag being buried in the soil and affecting the quality of asphalt surface treatment. The rest of the dam crest is afforested and beautified by combining arbor, shrub and grass, and by combining plane greening with vertical greening, so as to improve the environmental quality and enrich the landscape types.
3. 1.2 dam slope prevention measures
The dam slope is mechanically formed, covered with woven bags, and filled with waste soil to prevent soil erosion caused by wind; After the construction, the woven bags used for bedding will be removed and recycled to avoid the woven bags being buried in the soil and polluting the soil. After the completion of the main project, the dam slope will be afforested by planting turf and three rows of trees.
From the point of view of soil and water conservation, the greening project avoids the bare land, increases the vegetation coverage and improves the ecological environment, which fully meets the requirements of soil and water conservation. Moreover, it provides a beautiful and comfortable workplace for employees through greening and beautification, which is of great significance for improving the work efficiency of employees.
3.2 Engineering Protection of Pumping Station
The pumping station is built in the southeast corner of Hengye Reservoir, 80m away from Nanba. In the process of water lifting, the main canal of Chaohe River may change its flow direction, resulting in lateral scouring, scouring and even collapse of the canal bank. Therefore, 50-meter-long slurry block stone slope protection is arranged upstream and downstream of the intake. Through this measure, the lateral erosion of water flow caused by water lifting can be effectively controlled, which not only prevents the danger of canal bank collapse, but also ensures the smooth progress of water intake project and meets the requirements of soil and water conservation.
3.3 Greening around water supply pumping station and office building
Within 50 meters near the water supply project and the office building, the greening project is mainly to plant turf, and flowering shrubs and small trees are appropriately planted; Outside 50 meters, planting windbreak belts, using mixed trees and shrubs and mixed needles and broadleaves, not only has the windbreak effect of tight structure, but also has the protection distance of sparse structure. From the point of view of soil and water conservation, the coverage of surface vegetation around the main project has been increased, effectively curbing wind erosion and preventing dust.
4. Implementation plan and completion period of soil and water conservation measures
According to the "three simultaneities" in the soil and water conservation law, the soil and water conservation scheme should be implemented simultaneously with the main project. However, in the actual production and construction process, due to the progress of the main project and the characteristics of soil erosion, the engineering measures of soil and water conservation scheme should be completed simultaneously with the main project, and the plant measures should be implemented and accepted by stages, but not more than one year.
5. Benefit analysis of soil and water conservation
According to the purpose and requirements of the scheme design, through the implementation of the scheme, more than 90% of the soil erosion area in the project area can be effectively controlled, and the excavation surface, exposed surface and vegetation destroyed during construction around the reservoir can be protected, so that the whole ecosystem tends to be stable. The waste soil produced in the process of engineering construction is temporary waste soil, which is used for foundation backfilling and yard backfilling after taking materials. Temporary engineering measures shall be taken during temporary stacking to effectively block the spoil and avoid soil erosion. After the implementation of the plan, the grassland was restored, trees and shrubs were planted, and the forest and grass coverage rate was improved. In this way, not only the soil erosion in the project area can be effectively controlled, but also the arrangement of a large number of plant measures will obtain direct economic benefits. At the same time, the construction of soil and water conservation projects can improve the local residents and government's understanding of soil and water conservation, provide a certain number of employment opportunities for local people, and help improve people's living standards. The restoration and increase of vegetation will greatly increase soil moisture, improve soil physical and chemical properties, improve soil fertility, and adjust inter-seasonal water quantity and regional microclimate at the same time, which is conducive to the improvement of environmental air quality and the benign cycle development of the ecosystem in the project area.
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