The Hanjiang River has three sources, namely Shui Yang, Nanhe and Qushui. In the past, it was generally believed that the Central Plains was the positive source, that is, the overflowing water originated from Fan Zhongshan in Ningqiang, Shaanxi, China. The flow of overflow water is much smaller than that of Daiyu River and Qushui River, but the valley is much wider than both. Near Liejin Dam, the overflow level is only 10 meter wide, but the width of the valley is 2000 ~ 3000 meters. The valley slopes on both banks are gentle, and the river bed slope is also very gentle, unlike the deep valleys at the upstream starting point of general rivers. The Hanjiang River flows eastward from Lijinba to Da 'anyi, forming a small watershed with a width of 1 1,000 meters. The difference between the local flood level and the low water level is only1-2m. It's just that rivers are scattered, water has no fixed channels, and fields on both sides of the strait are washed away and turned into wasteland. Then it flows into the canyon and develops into a basin in Xinpu Bay, similar to Daangang. Further east to Dangchang City, Nanyuan Nanhe Laihui, and Qushuipu, it originated in Liuba Qinling, Shaanxi Province, and Qushui Laihui, with an altitude of 26 10 meters, is the northern source of the southwest foot of Bai Zi. The basin area, length and water volume of the north-south source are larger than those of the middle source, but the valleys are very narrow canyons. After the confluence of the three sources, the Hanjiang River has the scale of a big river, and then passes through a canyon of about 10000 meters, reaches Gaojiaquan in the upper reaches of Wuhou Town, and enters the flat and open Hanzhong Basin. The Hanjiang River runs through Hanzhong Basin from west to east, with a wide valley and alluvial plains on both sides. The two banks near Mianxian County are about 3000 ~ 4000 meters away from the mountain. At low water level, the river is about 60 ~ 70 meters wide and the flood reaches 400 ~ 700 meters. Near Nanzheng, the flat land on the south bank is only 1000 ~ 2,000 meters away from the mountain, and the flat land on the north bank is more than10 kilometers. This river is very wide. At low water level, the river is about 300 meters wide and 3 ~ 5 meters deep. The width of the flood river is1000 ~ 2000m, and there are rows of sandbars in the river, with alluvial sand on the shore, which is easy to be washed away by running water and the river course is changeable. For example, in the 29th year of Guangxu (65,438+0,903), Dashui was in Jiangnan before, and now it is in Jiangbei, about 500 meters away from both sides. The terraces on both sides of the Hanjiang River Valley in this section are well developed. The terrace below10m is the first terrace-flat floodplain terrace. The second terrace is between 10 ~ 15 meters, which is not as flat as the floodplain terrace, but it is divided less; The third terrace is 30 ~ 40 meters higher than the river bed, and the ground division is relatively broken; The fourth terrace is 70 ~ 80 meters higher than the river bed and distributed sporadically; The fifth terrace is 200 meters higher than the river bed and is completely hilly. Hanshui River flows out of Hanzhong Basin and into the canyon section of more than 600 kilometers. The Hanjiang River is cut off sharply, with undulating mountains on both sides and narrow riverbed. The narrowest place is only 50 meters and the widest place is only 200 meters. The river flow is confined to steep valleys, and the current is swift, with a tendency of a thousand miles, and it is rich in water resources. Danjiangkou, Ankang, Shiquan on the main stream and Huanglongtan water control project on the tributary are all located in this narrow ravine. After flowing through Xun County, the Hanshui River flows through laohekou city, Gucheng, Xiangfan, Yicheng and Zhongxiang in the southeast, enters the downstream plain, crosses Qianjiang, Tianmen, Xiantao, Hanchuan, Caidian and other counties and cities, and joins the Yangtze River at the Longwang Temple in Wuhan. Hanjiang River [Shaanxi, China]-Hydrological information The Hanjiang River is divided into upper, middle and lower sections. Above Danjiangkou is the upstream, with a length of about 925 kilometers and a catchment area of 9.52 square kilometers. Crossing between Qinling Mountain and Daba Mountain, the valley often intersects with the strike of rock strata, with an average slope of 0.6‰. Canyon and basin appear alternately, the river course is tortuous, the beach area is water, and there are many important beach hazards 100. The river width in the basin section is generally 200 ~ 300m, the valley depth in the canyon section is generally 300 ~ 400m, and the river width is only tens of meters. Among them, between Yangxian and Shiquan, canyons are the most concentrated. According to the natural conditions, this section can be divided into two small sections: Yangxian to Weimen is a deep canyon section. This section is the largest canyon on the main stream of the Han River, with a total length of about 53 kilometers, which is divided into upper and lower sections. The upper section is about 23km long, from Xiaoxiakou in Yangxian County to Zhu Huan Temple. After the Hanjiang River entered the small canyon, the river suddenly converged to 200 meters, and the mountains on both sides were higher than the riverbed 100 ~ 200 meters. The distance between Zhu Huan Temple and Weimen is about 3 0 kilometers. It is called the Golden Canyon, also known as the Grand Canyon, and it is the most famous canyon on the Han River. The Grand Canyon forms a big yoke, with a land-water distance of 30 kilometers and a land-water distance of only 9 kilometers. After the Hanjiang River enters the Grand Canyon, the mountains on both sides of the river are 300 ~ 400 meters higher than the riverbed, the inclination of the valley reaches 50 ~ 60 degrees, the narrowest part of the river is only 50 meters, and the difference between the highest and lowest water levels is 24 ~ 25 meters. There are more than 30 famous places in the middle of the river, among which Turtle Beach, Cage Beach and Jinliuzi are the most dangerous. Weimen to Shiquan. The valley from Weimen to Chazhen is very wide, roughly steep and slow, so if the Golden Canyon is sandwiched between two peaks, there is no room for manoeuvre. This section of the river is about 200 meters wide and the valley is 500 meters wide. There is a small basin formed by red rock series near Qixingba, which is slightly smaller than Shiquan basin. The valley from Chazhen to Shiquan is desolate, with a river width of about1.50m.. The peaks on both sides of the river are about 300 meters higher than the river, and the valley slopes are 50 ~ 60 degrees. Especially steep in limestone area, there are many caves, which are 30 ~ 40 meters higher than the river bed. There are many pebbles and moraines on the riverbed of this reach. The tributaries are short, mostly mountain streams. Danjiangkou to Zhongxiang is the middle reaches, about 270 kilometers long, with an average gradient of 0. 19‰ and a catchment area of 46,800 square kilometers. The river flows from east to west to southeast. Walking through low mountains, hills and hills, the flow rate slows down and the valley is slightly open. In dry season, the river width is generally increased to 300-400 meters, and in flood season, the river width is 2000-3000 meters, and the widest point can reach 5000-6000 meters. During the maximum flood period, the widest area extended to 8000- 10000 meters, and all the plain areas were flooded. The riverbed is wide and unstable, with changeable erosion and siltation and numerous beaches. After the Hanjiang River entered the plain, the flow rate suddenly slowed down, and there was a lot of sediment in the river, which often rushed up and changed a lot. During the flood, the river bed was washed away violently. For example, Xiangyang Station1952, April 29 ~ 165438+1October 10, measured the cross-section change in flood period16 times. At the beginning, the river bottom elevation was 665,438+0.9 m, with repeated scouring and silting in the middle, reaching 565,438+0.8 m at the lowest, silting back to 665,438+0.3 m after the flood, and the longitudinal section returned to a stable state. There are 143 sandbars and 38 beaches in this section, with an average of one sandbar or beach every 1.7 km. These sandbars and beaches are constantly changing. For example, there are six sandbars from Raojiaying to Wangjiahuan near Sanguan Hall, 1944 to 1953. The riverbed above Xiangyang in this section is composed of big stones, coarse sand and fine sand, and the riverbed below Xiangyang is sandy. Except for some places (such as Xiangyang Laolongdi), there are almost no dikes on both sides of the valley. Therefore, due to frequent floods, the natural dams along the river are gradually raised, and the farther away from the river, the lower the terrain, and the lowest to the hillside, resulting in the inversion of the valley landform. Local residents also know this, and there is a proverb that "it is too cold at the top and too cold at the bottom".
Below Zhongxiang is the downstream, about 382 kilometers long, with an average gradient of 0.09‰ and a catchment area of 6.5438+0.7 million square kilometers. Walking through Jianghan Plain, the water flow is slow, the river bed is shallow, and the meandering is extremely developed, so it is said that "the meandering is like Han". The central mileage of each river is much longer than the straight line distance. The total length of the Hanjiang River from Zhongxiang to Hankou is 388 kilometers, and the straight-line distance is only 2 10 kilometers, with a difference of 142 kilometers. Another example is Dongjing River. From Zekou to Dunkou, the length of the river is 2 10 km, and the linear distance is only 136 km. Since the Ming Dynasty, China has been building dikes on both sides of rivers, and the rivers along the way converge, with the upper width and the lower width forming a funnel shape. The width of Hanjiang River in Zhongxiang area is 3000 ~ 4000 meters during normal flood. From Zekou to Zhangjiegang, the river width is about 1000m, and it is reduced to 500m below Zhangjiegang to Mayangtan. The distance from HuangXinchang to Xiantao is reduced to 350m, which is even narrower below Xiantao, and the narrowest point is only 100m near Wuhan. During the flood season, the upstream water flows into the Yangtze River from the downstream mainstream and the Dongjing River on the right bank. The discharge section of the riverbed near Taozhubu in the upper reaches of Dongjing River is 2300 square meters, while that near the north mouth of the lower reaches is only 1700 square meters. This deformed state of wide upstream and narrow downstream makes the allowable flow of the river smaller and smaller. For example, the allowable flow of the Hanjiang River in Nianpanshan Mountain in Zhongxiang is 27,000 ~ 30,000 m3/s, while the allowable flow below Dujiatai Mountain in Xiantao is only 5,250 m3/s, and the upstream flow is very large, resulting in an extremely unbalanced flow of flood water, which is the biggest feature that distinguishes the Hanjiang River from other rivers. Once a flood occurs, the flood surges and breaks its banks, which is one of the basic reasons for the serious flood in the lower reaches of the Han River. In this section, there are vast plains and many lakes below 35 meters above sea level on both sides of the river. The plains are banded and parallel to the river. 35 ~ 50 meters are river terraces, hills and hills. The terrain along the Hanjiang River, Dongjing River and Yangtze River is generally relatively high, and depressions are often formed between rivers, which are depressions and lakes where accumulated water gathers. For example, on the left bank of the Han River, there are depressions in the Tianmen River Diaocha Lake between the main stream and the northern hillside, in the Tongshun River Basin between the right bank of the Han River and the Dongjing River, and in the Neijing River (Zhongxiang River) Honghu Lake between the Dongjing River and the Yangtze River. These depression zones are usually southeast. Where the plain is adjacent to the terrace, the terrain is also very low, and it often becomes a lake belt with depressions on the edge of the hillside during the lake dispersion period, such as Zhongxiang Shuijia Lake, Tianmen White Lake, Xiaogan Tongjia Lake and Wild Boar Lake. Siltation in the lower reaches of Hanjiang River is extensive and serious. Historically, there have been many caves and tributaries on both sides of the main stream of the Han River. Later, due to more and more serious siltation and blockage, most tributaries were silted up. In the Ming Dynasty, in order to maintain Wang Xian's tomb, the caves on the left bank were blocked, so the flood on the right bank became more and more serious. During the Ming and Qing Dynasties, in order to protect the ancestral graves, Zhang, a great scholar, built a Shayang levee on the right bank, blocking the Maojiangkou of the Yangtze River (now Honghu County), so most of the caves on the right bank were blocked, and the Han River was limited to a narrow dry dike, with the maximum flood discharge exceeding 4-5 times the safe flow. Coupled with the jacking of the Yangtze River, the Hanshui River often causes floods due to poor flood discharge. After 1949, in addition to building dikes along the whole line, large-scale water conservancy projects such as Ankang, Danjiangkou and Huanglongtan were built on the main tributaries in the upstream, and large-scale drainage project in Hanbei and flood diversion project in Dujiatai were built in the downstream, which reduced the flood disaster and provided the impetus for irrigation, shipping, power generation and aquaculture. With a total length of1.577km, the Hanjiang River is the longest tributary of the Yangtze River, with a drainage area of1.5900km2.. Among the main tributaries of the Yangtze River, second only to Jialing River, the average annual runoff is 56.3 billion cubic meters, the average annual estuary flow is 1.820 cubic meters per second, the natural drop is 1.964 meters, and the theoretical hydropower reserve is 65,464. Because the middle and upper reaches of the Han River come from mountainous areas, the current is swift, the erosion is strong and the sediment transport is large. The annual average sediment transport capacity of Nianpanshan Station is 2.39 kg/m3, with an annual sediment transport capacity of 65.438+300 million tons, the maximum sediment transport capacity of 263 million tons (654.38+0964) and the minimum sediment transport capacity of 22.3 million tons (654.38+0996).