IMPORTANCE OF THE RED RIVER TO HANOI

          Hanoi is located in the center of the Red River Delta which is accreted by the Red River and Thai Binh River systems. The development of Hanoi is associated with rivers, of which the Red River is the largest. The Red River is like a mother river that accretes alluvium for fertile soil and green trees, contributing to create a cultural space named Hanoi.

          The Red River is the 26^th largest river in the world and the 12^th in Asia. It originates from the Weishan mountain range ( 1176 m high) in Yunnan province, China, and is nearly 1200 km long. It flows through the North of Vietnam before entering the Gulf of Tonkin. The Red River enters Vietnam at Ha Khau, approaches Hanoi at Phong Van commune, Ba Vi district, and ends at Quang Lang commune, Phu Xuyen district.

The Red River is shaped like a paper fan, with a steep riverbed upstream that decreases downstream. Therefore, in the rainy season, the water rises very quickly but recedes very slowly. Its annual volume of water flowing into the sea is very large, about 120 – 160 km³ per year. The volume of sediment transported by the Red River is from 50 to 130 million tons per year, ranking it 12^th among alluvial-bearing rivers in the world.

Photo by Pham Trung Hung and Le Chi Cong

The section of the Red River flowing through Hanoi is winding and meandering so it is also known as Nhi Ha (earlobe-shaped) River: “Nhi Ha flows around the north to the east.” The widest section flowing through Hanoi is in Van Coc Commune, Phuc Tho district, and the narrowest is in Chem village, Bac Tu Liem district.

The hydrological regime of the Red River is shown in two distinct seasons: the dry season and the wet season. In the dry season, from November to April next year, the weather is cold, dry and less rainy. As the river’s water is mainly groundwater, its water level drops to reveal the sandy shores and sand dunes in the middle of the river. A special feature of the Red River is that along the river there are many alluvial flats, of which the largest inhabited one is in the river section that flows through Hanoi, which people here commonly call Bai Giua (as known as Trung Ha). Bai Giua divides the river in this section into two streams, so the Red River here is also known as Nhi Ha (the two rivers). During this season the river's flow is less volatile and only accounts for 20-30% of the total flow in the year. However, due to the construction of reservoirs in the entire Red River system the water flow downstream has decreased significantly. Sometimes the water level is so low that many sections are reduced like canals. There are sections where people temporarily bridge out to the alluvial flats to grow sugar cane, corn, potatoes etc. or walk out to catch fish without needing boats. For generations, people living along the river have grown crops thanks to the fertile alluvium of the Red River and taken advantage of working on the flats. In the flood season, they cannot do these jobs.

Photo by Nguyen Xuan Chinh

Photo by Nguyen Phu Duc

The flood season is usually from June to October, with the highest water level in August. The water flow during the flood season accounts for about 70-80% of the total flow in the year. The total annual volume of Red River water flowing through Hanoi is about 111.7 billion m3. On average, each hectare of land receives hundreds of m3 of water annually. This proves that Hanoi is a land with rich water resources. However, because the flow is concentrated during the rainy season, there are often large and rapid floods, which cause dyke breaks and flooding. In the past, when there were no large hydropower projects upstream, the Red River had big floods almost every year. According to statistics from the 13^th century to the 19^th century, there were 188 years of great floods that broke the Red River dykes.

Although the section of the Red River flowing through Hanoi is very short compared to its total length, it plays a huge role in the formation of the landscape and typical culture of this land. After thousands of years of painstakingly accreting alluvium, the Red River has turned Hanoi into a rich area, attracting craft villages to come and create a bustling capital: “It is best to be near the market, then near the river”. Previously, when roads were not developed, people mainly transported goods by river and there were many craft villages formed along the river, which was convenient for transporting goods to localities. Hanoi is located in the center of the Northern Delta, and the Red River in Hanoi is the regional water traffic hub (thanks to the fan-shaped river system). Cargo and passengers from the northeast, northwest or seaports are transported to Hanoi and then moved to other places. It can be said that, besides creating a fertile arable land for agricultural development, the function of the Red River in traffic and economic development is very important to Hanoi.

Lê Chí Công - Nguyễn Minh Tú