Why Do We Track River Flow in Yên Bái?

1. Where is Yên Bái?

Geographical Background

Yên Bái is a province located in north-eastern Vietnam, approximately between 21.87°N latitude and 104.91°E longitude. It is surrounded by Thái Nationwide Province to the east, Tuyên Quang Province to the southeast, Sơn La Province to the southwest, and Điện Biên Province to the west. The province is representative for its mountainous landscape in which the Hoang Lien Son and Truong Son ranges take up the province. The mountains are extremely steep with deep, coarse valleys. Yên Bái has a subtropical highland climate with distinct seasons with May to October rainy season and November to April dry season. Topography and climate together exert serious impacts on the river systems of the province.

Humanities and culture

Yên Bái is rich in culture with its cultural heritage being firmly rooted in the multi-ethnic community. The province has a number of ethnic minorities such as the Thái, H'mong, Dao, and Kinh, all of which contribute significantly towards its being multicultural. The local culture here is a bedrock thing with the traditional festivals being celebrated in great enthusiasm with festivals like the Thái People's New Year (Tết Thái) and the H'mong traditional festivals. The celebrations involve traditional dance, music shows, exquisite costumes, and special cultural rituals.

The way of life and tradition of these ethnic minorities determine the local architecture. Stilted houses, for example, which are common among Thái people, are a perfect example of traditional dwellings. Handicrafts like exquisite embroidery, weaving, and silverwork typical of Yên Bái are likely to end up being sold in the local markets. The province's cooking cuisine, determined by its natural environment and ethnicity, is dominated by dishes prepared from locally found raw materials like wild vegetables, game, and river fish.

Hydrology and River Overview

Red River (Sông Hồng) and its tributaries form the vast river systems of Vietnam in Yên Bái. Red River is among the most important rivers of Vietnam. Red River has its source in Yunnan Province in China and flows through Yên Bái to the Gulf of Tonkin. River and the tributaries, such as the Chay River, play an important role in the environment of the province and man's utilization in Yên Bái.

The rivers are important in a variety of uses. The rivers offer domestic, agricultural, and industrial water. The floodplains of the river are also fertile and offer the cultivation of crops like rice, maize, and vegetables. The rivers also offer a transport facility, conveyance of human beings, and commodities, especially during the pre-modern era. Additionally, they hold numerous water bodies with different aquatic species upholding the fisheries of the area. However, the rivers are threatened with pollution by industrial effluence, agricultural run-off, and forest cover-caused soil erosion that have probable impacts on water quality and river ecosystem health.

2. What is the River Flow Near Yên Bái?

Influencing Factors

Precipitation and Runoff

The subtropical highland climate of Yên Bái greatly influences the run-off of its rivers. In rainy season, heavy precipitation, sometimes in excess of 1,000 - 1,500 millimeters annually, generates enormous run-off. This elevates its river levels and velocities. On the other hand, there is sudden decrease in precipitation in dry season, with decreasing river flows and water levels. Year-to-year variations in volumes of rainfall can create erratic fluctuations in river flow regimes, which are a challenge to water management, flood control, and supply of a stable amount of water.

Landform and River Morphology

Mountainous terrain of Yên Bái gives the rivers a high gradient, resulting in high-energy water, especially along the upper reach. Incising the country while flowing through the valleys, the rivers carve out deep gorges and rapids. The twisting and constricted nature of the river courses in the mountains creates rapid-flowing water with intense currents and turbulent waterflows. In the lower - reaching portions, the slope becomes reduced, and the rivers decelerate, dumping sediment and developing wider floodplains. Human - built structures such as dams, bridges, and irrigation canals have also been constructed along the rivers, altering their natural directions of flow and creating local water levels and velocities at times.

Reservoir Operations

Dams and reservoirs on the Red River and its tributaries upstream and in Yên Bái exist. They are mainly utilized for water storage, hydroelectric power, and irrigation. Regulated releases of water from such reservoirs upstream significantly influence the rate of river flows in Yên Bái. During periods of peak-demand water or low rainfall, reduced upstream water releases result in reduced flows of rivers in the province, affecting water supply, navigation, and the environment. On the other hand, releases of abuse in water during the rainy season lead to flooding in the downstream region, which is dangerous to human life and property of Yên Bái people.

Historical Hydrological Events

There has been some significant flood history in Yên Bái. Heavy monsoon rains and dam water releases of water farther upstream in 2017 caused widespread flooding across much of the province. Dispatches from the Vietnam Disaster Management Authority reported that vast expanses of farm land were flooded, thousands of people lost homes, and roads, bridges, and houses were destroyed. The Red River and its tributaries breached, flooding low-lying villages and freezing economic activity. Such prior events are analyzed to develop the right flood-mitigation strategies, upgrade drainage facilities, and increase the province's resilience against future hydrological disasters.

3. How is River Flow in Yên Bái Observed?

Traditional Methods

Surface Drift Float Method

Surface drift float method is an easy method to compute river flow. A floating body, e.g., a buoy or a piece of wood, is dropped on the river surface. The time elapsed in the float traveling a known distance is measured, and dividing the distance by the time yields the surface velocity of the river. But it yields information of surface flow only and is very susceptible to wind, which causes distortion in data, resulting in faulty velocity measurements. It also gives no hint of the flow at different depths of the river.

Anchored Boat Technique (Staff Gauge / Current Meter)

A boat is anchored in a location in the river in the anchored boat technique. Staff gauge is utilized in water level measurement, and a current meter is permitted to drop at various levels in the river for measuring the speed of water. A number of velocity readings are taken over the cross - section of the river and, by finding out the cross - sectional area and then multiplying it with the mean velocity, one can compute the river discharge. This is a more accurate procedure but time - consuming, labor - intensive, and unsafe, particularly in the high - velocity and frequently turbulent Yên Bái rivers.

ADCP Overview: Acoustic Doppler Current Profiler (ADCP)

Acoustic Doppler Current Profiler (ADCP) is a newer, more effective method of river flow measurement. The ADCP flow meter is non-invasive, and sound waves are utilized to measure water velocity at varying depths. ADCP can obtain continuous top-down river flow profiles within a reasonable time and describe river flow properties more accurately than the traditional methods. ADCP is a simple technology that can supply accurate and credible data, which are extremely significant to effective water resource management, flood forecasting, and ecological research in Yên Bái.

4. How Does ADCP Work According to the Doppler Principle?

An ADCP operates on the basis of the Doppler effect. It releases sound waves of a specific frequency into the sea. When sound waves strike moving particles in the sea, such as sediment, plankton, or water molecules, the frequency of the returning sound wave is changed. If the particles are moving towards the ADCP, the frequency of the returned waves is greater and, if they are moving away, the frequency decreases. With precise measurement of this change in frequency (the Doppler shift), the ADCP can be used to estimate water velocity at several depths. Several transducers in the ADCP measure velocities in various directions, from which three-dimensional structure of the flow in the river is derived.

5. What Is Needed for High-Quality Measurement of River Flow in Yên Bái?

Equipment Requirements

Adequate ADCP measurement of Yên Bái rivers needs some equipment specifications. Due to the harsh conditions of the rivers, including high-velocity waters, high sediment transport loads, and potential impact from the mountainous environment, material reliability is crucial. ADCPs made from heavy-duty corrosion-resistant metals like stainless steel or titanium are suitable to withstand the rough environment. Light and compact design is also preferred as it supports easy deployment and transportation, especially in distant areas away from the city and in mountains. Cost-effectiveness is also a primary factor, as this will enable greater application of the technology for general river flow monitoring.

6. How to Choose Suitable Current Measurement Gear?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: Eligible to conduct large - scale surveys of the Red River and its tributaries in Yên Bái. It can quickly measure river discharge along long reaches and chart out the flow patterns along sections of the river. As the boat passes along the watercourses, the ADCP is able to continuously monitor data and provide a general idea of the behavior of flow.
• Bottom - Mounted (Fixed) ADCP: Suitable for long - term continuous monitoring. It can be installed on the riverbed at some locations to collect data for long durations, allowing for the calculation of long - term flow tendencies, seasonal flows, and the effects of various factors on the river flow.
• Cable - Way ADCP: Where cable - way facilities are available along river reaches, cable - way ADCP can be suspended and walked across the river for measurement at different locations. Cable - way ADCP is effective where boat - based measurements are inconvenient due to river terrain or strong currents.

Working Frequency

• 600 kHz ADCP: A 600 kHz ADCP represents a good trade-off between range and resolution with a horizontal range of 70 meters. It is suitable for the majority of Yên Bái river reaches to achieve accurate measurements of the flow velocity at different depths.
• 300 kHz ADCP: For a wider range of up to 110 meters, a 300 kHz ADCP is appropriate for deeper and wider sections of the rivers, especially in the lower section where the river widens.

Brand Recommendations

Well-established globally ADCP brands are Teledyne RDI, Nortek, and SonTek, which provide high-quality and dependable products that have been used in various hydrological research and monitoring studies. For an affordable option, the ADCP manufacturer Chinese company's "China Sonar Panda ADCP" is the best. Constructed of all - titanium alloy, it is highly durable and reliable, making it perfectly suited to endure the harsh aquatic environment around Kochi. Being an "affordable ADCP", it gives excellent high - quality performance without cost. To know more, check https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.