Brief introduction of nenjiang river

Nenjiang River originates from the south side of the middle section of Ilhuli Mountain in Daxing 'anling, and its source is Nanweng River (also known as Nanbei River). Its source is 1030 meters above sea level, and the source is snowmelt and a mesh stream full of spring water. From the source of the river, it flows from northwest to southeast at 127.2km, and then joins the Ergen River and flows south, which is called the main stream of Nenjiang River. After that, the water flows from north to south through Oroqen Autonomous Banner, Qiqihar City, Da 'an City and other 15 cities, counties (banners), and joins the second Songhua River originating from Tianchi Lake in Changbai Mountain near Sancha River in Songyuan City, Jilin Province. From Heyuan to Sanchahekou, the total length is1370km, the main stream is 975km long, and the drainage area is 282,748km2.

Nenjiang River is divided into three sections according to its topography, landform and valley characteristics: upstream, middle and downstream. From the source of Nenjiang River to Nenjiang County, it is the upper reaches, with a river length of 66 1 km. Heyuan District is a famous mountain forest area in Daxing 'anling, with dense forests, numerous swamps, narrow river valleys, large river slopes and fast-flowing water. The water surface width is100 ~ 200m, and the river gradient is 14 .2‰, and the river is composed of pebbles and gravels. The river channel below the source area gradually widens, the river channel gradient drops by 3. 1 ‰ ~ 3.6 ‰, tributaries flow one after another, the water volume increases, and the width of the river valley can reach 5 ~ 10 km. From Nenjiang County to Nierji (formerly known as Buxi) in Molidawa Daur Autonomous Banner, it is the middle reaches, a transition zone from mountainous areas to plains, with a length of122km. There are many low mountains and hills on both sides of the river, the terrain is flatter than that on the upper reaches, and the two sides are asymmetrical, especially on the left bank, where the valley is very wide. There are few tributaries in the middle reaches, except that the river passes through Nenjiang County for 4 kilometers and the larger tributary on the right bank flows into the main stream, the rest are small tributaries or small mountain streams. Nierji to Sanchahekou is the downstream reach, with a length of 587 kilometers. This section of the river flows into the vast Songnen Plain. The river is winding, with many beaches, sandbars and tributaries. The rivers are mostly reticulate, and the beaches on both sides are very wide, with the widest point reaching more than 10 km and the maximum water depth of 7.4 meters. Foam, wetland and oxbow lake are widely distributed on the beach. The average gradient of the upper reaches of Qiqihar City is 0.2 ‰ ~ 0./kloc-0 ‰, and the water surface of the main channel is 300 ~ 400 meters wide and the water depth is 3 ~ 4 meters. The downstream river network is dense, with tributaries such as Nuo Min, Yarlung Zangbo River, Chu Er and Taoer River flowing into Nenjiang River on the right bank, and the vast area on the left bank is basically an inland closed flow area with large swamps, lakes and wet depressions. The height difference from Heyuan to Sanchahekou is 900 meters.

Most tributaries of Nenjiang River are on the right bank, and six of the eight tributaries with a basin area of 6.5438+0 million square kilometers are on the right bank. The tributaries on the left and right banks all originate from the branches of Daxing 'anling, form along the slopes of Daxing 'anling, and merge into the main stream from northeast to southwest or northwest to southeast. There have been many floods in Nenjiang River in history, most of which were caused by water from the tributaries on the right bank of the eastern slope of Daxing 'anling Mountains. Due to the topographical conditions, once there is a rainstorm in summer and autumn, a rainstorm center will often form. At the same time, because the middle and upper reaches of the main tributaries are mostly hilly areas that are easy to produce runoff, the runoff is large. In the past rainstorm or continuous rainfall, the water from the main tributaries has been injected into the main stream one after another, forming a major flood in the main stream. The thrilling 1998 Nenjiang once-in-a-century flood was thus formed.

The meteorological and hydrological elements of Nenjiang River have changed greatly within the year, between years and between regions. The maximum annual precipitation is 937.4 mm, and the minimum annual precipitation is152.5 mm. The annual precipitation is mainly concentrated from June to September, accounting for 82% of the annual precipitation, with July and August accounting for the largest proportion.

The average annual runoff of Nenjiang estuary is 22.5 billion cubic meters. The distribution of annual and inter-annual runoff is uneven. The maximum value appears from June to September, but the difference between the maximum value and the minimum value of the average flow in these months is 50 ~ 80 times; The difference between the maximum and minimum annual average runoff is generally 4 ~ 10 times, and the difference between the maximum and minimum is 30 ~ 60 times.

Nenjiang river basin belongs to the continental climate of cold temperate zone and semi-humid, with long and cold winters and short and rainy summers. The annual average temperature is 2 ~ 4℃, the lowest temperature over the years is -39.5℃, and the highest temperature is 40. 1℃. In winter, the freezing period of Nenjiang River is about 150 days, and the ice thickness is about 1 meter.

Nenjiang River Basin spans 6 cities (leagues) and 26 cities and counties (banners) in Heilongjiang Province, Jilin Province and Inner Mongolia Autonomous Region. The left bank is all in Heilongjiang Province, and the right bank is mostly in Inner Mongolia Autonomous Region. There are only the lower reaches of Taoer River and the lower right bank of Nenjiang River in Jilin Province.

In order to build water conservancy projects and eliminate water disasters in Nenjiang River basin, five large reservoirs and 28 small and medium-sized water storage projects have been built, 174. The Nierji Reservoir, a large-scale control project, is being built in Molidawa Daur Autonomous Banner, the main stream of Nenjiang River. After the completion of the reservoir, the flood control benefit is very significant.

In order to solve the problems of water use in Daqing Oilfield, agricultural irrigation water use in Songnen Plain and people's domestic water use, develop fish farming, reed farming and improve grassland, since the early 1970s, three water transfer projects, namely "three major water transfer projects", have been invested and constructed successively. The "Three Diversion" from Dukou, Laha Town, nehe city to the hinterland of Songnen Plain, the main stream of Nenjiang River, has a project control area of 37.5 million mu, the length of the main diversion canal is 45 kilometers, and the diversion flow is 100 m3/s. The "South Transfer Project" is located on the left bank of Nenjiang River in the southwest of Songnen Plain, with a control area of 3,600 square kilometers. "Yin Zhong" is located in the closed flow area at the end of Wuyuer River and Shuangyang River in Songnen Plain. The project covers an area of 7,500 square kilometers, with a length of 150 kilometers from north to south and a width of 50 kilometers from east to west. Due to the introduction of Nenjiang River water, the degraded grasslands, reduced reeds and disappeared swamps in the "Three Diversion" control area have recovered their vitality, birds have come here to live, fisheries have been greatly developed, and grain output has been improved.