Question 1: The basic meaning of river course is divided into five grades, namely, first-class river course, second-class river course, third-class river course, fourth-class river course and fifth-class river course. According to the river classification method, most of the first-class and second-class rivers span two or more provinces, which have a decisive impact on the overall national economic and social development, so such rivers should be identified by the Ministry of Water Resources; Third-class rivers mostly affect one province or neighboring provinces, and their importance is slightly lower than that of first-class and second-class rivers, but they also have a considerable impact on the regional national economy. In order to make the inter-provincial standards generally consistent and facilitate the classification of inter-provincial rivers, the Ministry of Water Resources should entrust the water conservancy (hydropower) departments (bureaus) of the provinces (autonomous regions and municipalities directly under the Central Government) to negotiate and report to the Ministry of Water Resources for identification; Four or five types of rivers are determined by the water conservancy (hydropower) departments (bureaus) of the provinces (autonomous regions and municipalities directly under the Central Government). The river level can be determined by stages and batches, and its level can also rise and fall due to changes in conditions. The change procedure is the same as the identification procedure. Considering that it is impossible to make comprehensive provisions in the classification, the Ministry of Water Resources can directly specify the grade of the river course under special circumstances. The management of cross-border or international border rivers involves bilateral or multilateral relations between countries, and domestic methods can not be completely used, so they can not be classified temporarily. The basic cause of ancient rivers is river diversion. River diversion is the result of both internal and external factors. The external causes include the uplift or subsidence of a certain reach caused by tectonic movement, the blockage of the river by glaciers, collapses and surf, and the artificial opening of another river. Among them, tectonic movement can divert the river on a large scale, and the abandoned reach may be lifted and located in the current basin, or it may be buried by later sediments due to subsidence. Most of the diversions caused by rivers themselves occur in plain rivers with strong accumulation. The riverbed of this river gradually silted up and the slope decreased, so that it was too late to discharge when the flood occurred and flooded out of the river. The water flowing out of the river quickly accumulates sediment on both sides of the river, forming a natural dike. Over time, the river and its natural dams on both sides will be higher than the ground. When a natural dam breaks somewhere, a deep river will be washed out downstream. After the flood subsides, the river will flow along the new channel, and the original channel will become an abandoned ancient channel. The lower Yellow River in China is a river with good siltation and migration, so there are countless ancient rivers left on the North China Plain. Some ancient rivers formed by river action are also caused by river erosion. For example, the winding of the plain leads to the bending and straightening of the flood, leaving an ancient river like an oxbow lake. There are many such ancient rivers left on both sides of Jingjiang section in the middle reaches of the Yangtze River. Type ① buried ancient river course is formed in the river where the ground sinks and the riverbed is not easy to deposit. The ancient river course is buried with ground materials. (2) The channel of the ancient * * * river, and the surface of the ancient * * * river has not been landfilled with materials. Including the following three types of ancient rivers: a. strip-shaped highland ancient rivers, mostly formed by surface rivers diverted; B. The ancient channel of Oxbow Lake is formed in a meandering river; C the ancient branch road of Jiang Xinzhou was formed in a sandy river in Jiang Xinzhou. Features and search methods The most important feature of the ancient river channel is its associated riverbed facies deposition, with pebbles or coarse sand at the bottom and sand or silt at the upper part. On the vertical section, the order of particle size is coarse at the bottom and fine at the top. In longitudinal section, the upstream is thicker than the downstream. Looking for ancient rivers on the surface of * * * can be directly pursued on the spot or interpreted according to remote sensing images. Searching for buried ancient rivers must be determined by drilling and geophysical methods from the distribution and lithology of their sediments. I. Dredging by diversion cofferdam method. The common method of river dredging is to conduct cofferdam diversion in stages in the river, and calculate the cross-section form and size of cofferdam according to the actual situation of construction site and Xie Cai formula. A water guide? On the other side, dry land dredging is carried out. Or intercept the river upstream and discharge the water from the construction area through pipelines or other drains? Dry land operation should be carried out in the construction area. Construction is mainly mechanical, and excavators are generally used for excavation and dumping, and dump trucks are loaded and abandoned in the spoil ground. Second, dredgers dredge. It is mainly suitable for the smooth channels around the reservoir all year round, with soft sediment and inconvenient transportation, which is not conducive to dry field operation. It uses mechanical dredging to remove polluted sediments from rivers, lakes and reservoirs. During dredging, during transportation and after dredging, it has little impact on the environment and surrounding water bodies. On February 18, 2003, the largest underwater dredging project in China-Tianjin Haihe River comprehensive development dredging project started. This is also a typical dredging project using dredgers. Three, the river earthwork leveling method. It is suitable for rivers with serious sediment deposition, years of drought, serious vegetation destruction, large sandstorm, wide reach and great fluctuation. River earthwork leveling method has been well applied in the dredging of Yongding River and Chaobai River in Beijing, and the effect is good after the project is completed. & gt
Question 2: What is river dredging and what is its definition? The 50-minute dredging is to make the original river channel smoother, and to dig the river channel for the construction project.
Question 3: What does the old channel of the reservoir mean? After the reservoir is repaired, the hydrological conditions downstream of the reservoir will usually be changed, such as the maximum flow rate is greatly reduced and the flow rate is relatively more uniform. If it is a diversion reservoir power station, the downstream bend may be cut off. Do you mean this river? Don't feel safe just because there is no water. During the flood season, these rivers must be flooded! ! !
Question 4: What do you mean by river surface and river course? The river surface is the surface of the river, and the river channel is the general name of the width and length of the river.
Question 5: What do you mean by dead river area? It means that water can't exchange with the outside water, becomes static, has almost no oxygen, and there are too many microorganisms in the water, which is eutrophication.
Question 6: What do you mean by leaving the river? Waihe River refers to the river water used in different ways, such as industrial and agricultural water and urban domestic water.
River water penalty refers to the use of river water resources for water transportation, fishery, tourism, sand washing and ecological environment.