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■ Qiantang River
The largest river in Zhejiang province. In ancient times, it was called Zhejiang, Zhejiang Water, Zhejiang River and Zhishe River. It originates from the east slope of Liugujian in Huaiyushan Mountain, southwest of Xiuning County, Anhui Province, at the junction of Anhui and Jiangxi provinces (the elevation of Liugujian is1629.8m, and the elevation of its source is about1350m). The main stream flows through Anhui and Zhejiang provinces, enters Hangzhou Bay from the south exit of Zhangpu Changshan in Haiyan County, and reaches Xisanzha at the junction of Yuyao City and Cixi County. It has a total length of 605 kilometers and a drainage area of more than 48,800 square kilometers. Between 28 04' ~ 30 24' north latitude and117 39' ~12114' east longitude. The topography of the basin inclines from southwest to northeast, and the main stream flows northeast into Hangzhou Bay. The river is feathered.
The main stream is located in the upper reaches of Xin 'anjiang Hydropower Station. The fengcun River, which comes from the upper source, passes through the mountainous area in southern Anhui, reaches he cheng in Xiuning County, and joins Meixiyuan, which comes from Wuyujian in Huaiyushan and is called Dayuanxi. The tributary absorbed along Dayuanxi has a short and urgent flow. From Liukou River in Xiuning County to Xiao Yuan River to Tunxi City, the water is weighed. After reaching Hengjiang, a tributary of Tunxina, it is called Jianjiang, and it is injected from the north in Pukou, Shexian County. Pukou to Meicheng Town, Jiande County, Zhejiang Province is called Xin 'anjiang. A mountain stream belonging to the street corner of Shexian County.
Xin 'anjiang Hydropower Station to Fuchunjiang Hydropower Station is the middle reaches. Xin' an River flows to Meicheng and accepts tributaries Lanjiang and Tongjiang. The three rivers will form a "D" shape. Lanjiang River is the largest tributary of Qiantang River and one of the main water sources of Qiantang River. The upper reaches of Ma Jinxi originated from the northern slope of Qingzhidaijian in the south of Xiuning County. Najiangshan Port in Shuang Gang, Quzhou City is called Changshan Port. Changshan Port mostly flows through mountainous areas and belongs to a mountain stream river. Quzhou to Lanxi is called Qujiang (or Qujiang or Xin 'anjiang), and Lanxi to Meicheng is called Lanjiang. Qujiang River flows through Jinqu Basin, with wide channel and slow water depth. Leaving the Jinqu Basin, the riverbed becomes deeper and deeper. Tongjiang is a tributary from Meicheng to Tonglu, starting from Wushitan, about 7 kilometers below Meicheng, and entering the famous Qililong Gorge, with a total length of about 22 kilometers. After Fuchunjiang Hydropower Station was completed and impounded, the surface of Qililong River widened and the original shoal was submerged. Some rivers in Lanjiang and Tongjiang form reservoirs. After seven miles, the river widened.
Below Fuchunjiang Hydropower Station is the downstream. Influenced by tides, it belongs to Qiantang River estuary area. Yan Wen, from Tonglu to Xiaoshan County, is called Fuchun River. Its riverbed is open and stable, with slow flow and obvious accumulation. The floodplain is developed, which is basically unaffected by sand coming from the sea. From Yan Wen to Hangzhakou, the riverbed is wide and shallow, and the river is zigzag, so it is also called Jiang. The sluice is hereinafter called Qiantang River, and later refers to the whole river, which is characterized by surging tidal bore. Below Ganpu is Hangzhou Bay. The right bank of the main tributaries in the lower section is Huyuan River, Puyang River and Cao 'e River; There are Fenshui River and Luzhu River on the left bank.
Climate hydrology Qiantang River basin belongs to subtropical monsoon climate. Annual precipitation 1600 ~ 2000 mm, and the precipitation in the upper reaches of the main stream is higher than that in the hilly plains in the middle and lower reaches. Runoff recharge is mainly rainwater, and groundwater accounts for only a small amount. The total runoff of Qiantang River is 43 1 100 million cubic meters, and the runoff depth is 880 mm.
The seasonal distribution of runoff in Qiantang River is uneven, and the flow of flood and low water is very different. In most areas (the main stream is above Fuyang), the precipitation is the highest from May to June, and the maximum runoff of rivers is the same period. The runoff of Quxian Station from May to June accounts for 42.2% of the total annual amount. Lutzbu station accounts for 39.3%. The annual variation range of runoff is small, the coefficient of variation of annual runoff is 0.28 ~ 0.38, and the annual extreme value ratio is also small. The water erosion modulus of Qiantang river basin is 100 ~ 500 tons/km2/year. The high value is in Cao 'e River and Puyang River basins, and the low value is above Changshan Mountain. The average sediment concentration of Qiantang River is 0. 1 ~ 0.4kg/m3. The average annual sediment discharge is 6.68 million tons. This river is clear all the year round, and it only becomes turbid during the flood season. The salinity, hardness and alkalinity of river water are low.
Qiantang tide is one of the most famous tides in the world. Especially the August 18th of the lunar calendar is the most spectacular. The formation of tidal bore is closely related to topography. Hangzhou Bay is a typical comb-shaped estuary, and its width shrinks sharply from the mouth of the bay. Bay mouth 100 km wide, 20 km wide to the surface of Ganpu, and only 1 km wide to Hangzhou. When the tide goes up, the water body is sharply constrained, the tidal wave energy is highly concentrated, and the tidal range is significantly increased. The tidal range in Ganpu is twice that of the estuary. The average tidal range is about 5 meters, and the maximum tidal range appears in Ganpu, reaching 8.93 meters. At the same time, the longitudinal section of Qiantang River estuary is unique. The riverbed of Hangzhou Bay is flat, rising from above Zhapu, with the highest point between Qibao and Cang Qian, and the highest point is about10m higher than the baseline. The total length from Yan Wen to Zhapu is130km, which is a huge sand ridge uplift. Huge sandbanks make the riverbed above Ganpu rise rapidly, and the low water depth becomes shallow from the mouth of the bay, with an average water depth of 2 ~ 3 meters, sometimes only about 1 meter. In the process of tidal wave propagation, due to the gradual shallowing of the river bottom, the propagation speed of tidal peak is much faster than that of tidal valley, the slope of tidal front becomes steeper, the back wave slows down, the deformation of tidal wave intensifies, and a tidal bore is formed near Jianshan Mountain. The tidal bore is the largest near Haining, with a general height of 1 ~ 2 meters and a maximum height of 3.7 meters, which gradually weakens near Hangzhou.
When the Qiantang River is at high tide, seawater flows backwards, and a large amount of sediment is mainly carried by the Yangtze River and deposited in the estuary by seawater, which is the main source of sediment in sandbars. At the same time, the river bed is raised and the water depth is shallow, which seriously affects the benefits of estuary shipping and aquaculture. In order to prevent tidal waves, seawall projects, which are as famous as the Great Wall and the Beijing-Hangzhou Canal, have been improvised since ancient times, and have been continuously strengthened since 1949.
The cascade development and comprehensive utilization of the whole basin is rich in hydraulic resources, and the exploitable energy is about 2.05 million kilowatts. By the end of 1978, the developed installed capacity had reached 13 1.9 million kilowatts. The tidal energy in the estuary is greater. Since 1950s, Qiantang River has been developed by cascade. Reservoirs and hydropower stations such as Xin 'anjiang, Fuchunjiang, Huangtankou and Hunan Town have been built, of which Xin 'anjiang Hydropower Station has a total storage capacity of 22 billion cubic meters and an installed capacity of more than 650,000 kilowatts. Fuchunjiang Hydropower Station has a total storage capacity of 874 million cubic meters and an installed capacity of 297,200 kilowatts. Huangtankou Hydropower Station and Hunan Town Hydropower Station were built for two-stage cascade development of Wuxi River, a tributary.
Qiantang river is the main channel below Lanxi, which can be used for ships of 30 ~ 100 tons. Only offshore ferries are navigable below Hangzhou. Xin 'anjiang is an important waterway connecting western Zhejiang and southern Anhui. The waterway is interrupted at Xin 'anjiang Dam, and the upper and lower sections are navigable. The steam turbine can reach Tunxi, Anhui by tracing back to Xin 'anjiang. Other tributaries and reservoirs also have navigation mileage of different distances. The basin is densely populated and economically developed. The valleys on both sides of the Taiwan Strait are good agricultural areas. The mountains are rich in wood and bamboo. There is a vast beach in the estuary area.
At the end of 1988, a 7-kilometer-long river course was excavated in the northeast corner of Hangzhou, reconnecting the Qiantang River with the Beijing-Hangzhou Canal, realizing the connection between the Beijing-Hangzhou Canal and the five major water systems of the Yangtze River, the Yellow River, the Huaihe River, the Haihe River and the Qiantang River, expanding the direct distance of water transportation by 400 kilometers, and forming a water transportation network centered on Hangzhou.
The natural scenery of Qiantang River is intertwined with man-made buildings. Go up the Qiantang River, cross Fuchun River to Xin 'anjiang River, become a tourist attraction, and be listed as a national 1 batch of key scenic spots.
■ Qiantang River estuary
The estuary area of the strong tidal estuary is 274 kilometers from the tidal boundary Lutzbu to the mouth of Hangzhou Bay. It can be divided into three sections: Lutzbu to Wenjiayan, which is 83 kilometers long and controlled by runoff. There are many Jiang Xinzhou in the river, and the riverbed is relatively stable, near the estuary; Wenjiayan to Ganpu, 10 1 km, runoff and tidal current interact, and tidal bore and riverbed are changeable; Belongs to the estuary section; Ganpu, commonly known as Hangzhou Bay, is 90 kilometers long and has little impact on runoff. The width from Nanhuizui to Yongjiang at the mouth of the Bay is 100km, and the width of Ganpu section at the top of the Bay is 20km, which is offshore outside the mouth. There are many islands outside the mouth of the bay, which are called Zhoushan Islands.
In the early years of the Eastern Han Dynasty, Wang Chong first discussed the astronomical and topographic conditions for the formation of tidal bore in Qiantang River. In order to resist the invasion of tidal bore, seawall projects have been built one after another since the Tang Dynasty, and the project scale is huge. Since the 1950s, people have systematically investigated the hydrological sediment and river evolution in the estuary area. The large-scale reclamation project that began in the late 1960s had a great influence on the evolution of tidal bore reach.
About 6000 years ago, the mouth of Qiantang River was invaded during the last ice age, and then the sea level dropped. After continuous deposition, the north shore is the south wing of the Yangtze River Delta, and the coastline is in Jinshan-Wangpanshan-Ganpu line. In recent 2000 years, Hangzhou Bay has collapsed from the south to the north, with drastic changes. The south bank extends from Shaoxing, Shangyu and Hushan, a large area of land outside Zhapu and Jinshan collapses, and Wang Panshan falls into the bay. Because the tidal force is much larger than the river, the sediment is brought into a huge sandbar with a volume of 42.5 billion cubic meters between Zhapu and Wenjiayan, with a length of 130 km and a beach top 10 m higher than the baseline. The main material is uniform silt.
Qiantang River has a large runoff variation and a small sediment discharge. The season of incoming water and sediment varies greatly, with the incoming water from March to June accounting for 57% of the whole year, and the incoming water from June 18+00 is only 15.6% of the whole year. The annual average flow rate is 1468m (/s), and the measured maximum flow rate at Lutzbu Station is 29000m/s (65438++). The total annual runoff of the whole basin is 46.3 billion cubic meters. The average sediment concentration for many years is 0.2kg/m, and the annual sediment discharge is 7.03 million tons.
The tide is a semidiurnal tide. Because the width of Hangzhou Bay is sharply reduced from the outside to the inside, the tidal range along the way is increased. The average tidal range of Zhenhai on the south bank of the Bay Mouth is 1.69 m, that of Zhangpu on the top of the Bay is 5.45 m, and the maximum tidal range is 8.93 m ... The average inflow and outflow of Ganpu section is 654.38+0.4 million m/s, which is much larger than the inflow from the basin. The tidal range on the north shore is greater than that on the south shore, and Luchao Port is larger than Zhenhai 1.49 meters. To the west of Ganpu, the riverbed narrows and rises sharply, and tidal waves deform violently, forming the world-famous Qianjiang tidal bore near Jianshan. Tidal bore is the highest in Yan Guan (formerly called Haining). The tidal head is usually1~ 2m, and the measured maximum is 3m. The propagation speed of tidal wave is 8 ~ 10 meter per second. Tidal bore is extremely destructive. According to the measurement, the tidal bore pressure reaches 7 tons/m, and the concrete blocks weighing 25 tons placed on the spur dike head are sometimes washed away. The maximum vertical average velocity in Jianshan and Yan Guan areas is as high as 4 ~ 5 m/s, and in the reach above Yan Guan, the rising tide velocity is about twice as high as the ebb tide velocity. The sediment carried by tidal current varies with the velocity. The sediment concentration in Jianshan and Yan Guan is the largest, with the measured maximum sediment concentration as high as 5 1kg/m, and the average sediment concentration in Ganpu is generally 3-4 kg/m, and the average sediment discharge per tide is about100000 tons.
The diluted water of the Yangtze River has obvious influence on the distribution of salt content in Hangzhou Bay. In the sea area east of Jinshan, salinity is distributed horizontally, with high in the south and low in the north. Due to the strong tidal current, the mixing of salt and fresh water in Qiantang River estuary belongs to vertical uniform mixing type, and the boundary of salt water intrusion moves up and down with the runoff of Qiantang River. In dry season, salt water can be traced back to Hangzhou, which affects the industrial, agricultural and domestic water consumption in Hangzhou.
The river bed in the estuary is wide and shallow, with a low tide depth of1~ 3m and a wide intertidal zone. Under the action of strong pulsating tidal current diverging from the flow path, with the increase and decrease of the contrast between runoff and tidal current, the riverbed is severely deformed. In the autumn when the runoff is weak and the tide is strong, the main trough swings in the direction of rising tide, and in the season when the runoff is high, the main trough swings in the direction of falling tide. With the alternation of wet year and dry year, the swing of the main trough has also changed for many years. For example, from 1962 to 1969, the main trough near Jianshan Mountain oscillated for nearly 20 kilometers. During the swing of the main trough, the beach on the side hit by the mainstream quickly collapsed and retreated, and a record of 245 meters of high beach collapse was measured one day. The longitudinal erosion and siltation of riverbed also changes greatly, with the upper reach of Yan Guan being in flood season and the lower reach being in dry season. The average scouring and silting range of riverbed can reach 5 meters.
Since the 1960s, 900,000 mu of tidal flats have been reclaimed, which has narrowed the river bundles of more than 60 kilometers above Babao in Haining County by three quarters. There are excellent natural deep-water harbors on both sides of Jintang Waterway on the south bank of Hangzhou Bay, and a 6,543,800-ton dock of Beilun Port has been built. Shanghai petrochemical base has been built on the north shore. The Yangtze River, Qiantang River and other rivers are constantly supplying rich nutrients, making the sea area south of the estuary the largest fishing ground in China.
■ Qiantang river tidal bore
Tidal surge at the mouth of Qiantang River in Hangzhou Bay. It looks like an upright water wall, rolling in. The tidal range of Qiantang River estuary is very large, the estuary is wide funnel-shaped and the riverbed is flat, which leads to a sharp increase in the tidal range of the Pacific Ocean when it spreads to this area. The tidal wave introduced into Hangzhou Bay meets the river at the mouth of Qiantang River, and the wave front is greatly resisted, and the front edge of the wave crest is broken and enters the sand bar when it meets the water, so that the tidal bore is divided into two branches, East Lake and South Lake, and continues to advance to the mouth. Between Jianshan and Haining, sometimes a water column with a height above 10 meter can be stirred. The breaking tide peak is a rolling white wave, with a height of 1 ~ 2 meters, which propagates at a speed of 4 ~ 6 meters per second, and the tide level rises to more than 2 meters in a short time. Every year approaching the autumnal equinox coincides with the spring tide and rainy season, and the average sea level rises. The tidal range in Haining can be as high as 9 meters, and the tidal bore phenomenon is extremely prominent. In case of strong east wind or southeast wind, the tidal bore scene is more spectacular.
■ Qiantang River Bridge
The first double-deck truss girder bridge for highway and railway in China. Located in Hangzhou, Zhejiang Province. Built in 1937. Built by Mao Yisheng and Ying Luo. Total length1453m, main bridge1072m, consisting of 16 simply supported riveted steel truss girder with a span of 65.84m.. The south approach bridge is 38 1 m long and consists of a double-hinged steel truss arch bridge and a reinforced concrete rigid frame bridge. Because the quicksand at the bottom of the river is as deep as 40 meters and the tide of Qiantang River, the bridge construction project is very arduous. Three months after the completion of the bridge, before the Japanese invaded Hangzhou, China blew it up by itself, and War of Resistance against Japanese Aggression recovered after the victory.