Why Do We Measure River Flow in Phú Thọ?

1. Where is Phú Thọ?

Geographical Background

Phú Thọ is a province in the northern part of Vietnam at approximately 21.25°N latitude and 105.33°E longitude. The province is bordered by the Yên Bái Province to the northwest, Thái Nguyên Province to the northeast, Hưng Yên Province to the southeast, and Hà Nam Province to the south. The province's topography is a mixture of the hilly north and plains in the south forming part of the extensive topography of the Red River Delta. Phú Thọ has a tropical monsoon climate with a very discernible wet season from May to October and dry season from November to April. The combined topography and climate determine the hydrological features and river regimes of flow for the province.

Humanities and culture

Phú Thọ is also abundant with Vietnamese history and culture, and is known as the cradle of Vietnamese. It's reported to be associated with legendary Hùng Kings, who founded the first Vietnamese state. The province boasts famous Mê Linh Temple, a holy site where the Hùng Kings Temple Festival is traditionally celebrated annually with pilgrims and travelers from everywhere in the country. Traditional ceremonies, folk dances, and musical performances in the festival remember the legacy and contribution of the Hùng Kings.

Local heritage also pertains to the richness of ethnic communities residing in the area, i.e., the Kinh, Thái, and H'mong. Brocade weaving, pottery, and woodcarvings are but a few of the popular traditional handicrafts that demonstrate the resourcefulness and expertise of the populace. Phú Thọ cuisine, which is regulated by its agricultural fertility, comprises dishes cooked with locally-harvested rice, fresh produce, and river fish, instilling one with an appreciation for the region's natural bounty.

River and Hydrology Summary

The Red River (Sông Hồng) and two of its tributaries, the Chay River and the Thái Binh River, are extremely significant in Phú Thọ. The Red River, which is begun on the Tibetan Plateau and runs through China's Yunnan Province into Vietnam, runs through Phú Thọ to drain into the Gulf of Tonkin. The rivers form a very valuable system to the province's economy, ecosystem, and lifestyle.

The rivers are among the major sources of water for household consumption, agriculture, and industry. Large-scale rice cultivation is supported by fertile floodplains along the rivers, and Phú Thọ is a major agricultural province. They serve as a means of transport, facilitating the exchange of goods and people, and are home to diverse aquatic life, supporting the regional fisheries. But the rivers are also faced with issues such as industrial wastewater pollution, agricultural runoff pollution, and deforestation-induced soil erosion that deteriorate water quality and riverine ecosystem health.

2. What is River Flow Near Phú Thọ Like?

Factors Influencing

Precipitation and Runoff

The tropical monsoon climate of Phú Thọ is responsible for a major contribution to river flow. During the rainy season, heavy rainfall, typically more than 1,500 - 2,000 millimeters per annum, immediately elevates the runoff. This water supply causes the rivers to swell, with higher water levels and flows. In the dry season, rainfall significantly decreases, and the water levels and the river's flows reduce. Inter-annual variations in rainfall volume and duration generate irregular river regimes of flow, which present problems for water management, flood defense, and the provision of a constant supply of water.

Terrain and River Morphology

The diverse terrain of the province controls the nature of the rivers. In the northern areas of hilly terrain, the steep slopes cause rivers to run quickly, cutting deep valleys and rapids. When they reach the more level southern plains, the slope is reduced, the rivers slow and deposit sediment, forming extensive floodplains. The meandering path of the rivers, as well as man-made structures like dams, bridges, and irrigation canals, also disrupt natural flow patterns, causing local water level and velocity changes.

Reservoir operations

Construction of dams and reservoirs is done on the Red River and tributaries upstream and in Phú Thọ. These reservoirs are mainly utilized for water storage, hydropower, and irrigation purposes. Regulated upstream reservoir releases can also strongly affect river discharge in Phú Thọ. Low releases during peak water use or when there is little rainfall can lead to lower river flow, affecting supply of water, navigation, and river ecosystems. In contrast, poor management of water outflows during the rainy season could lead to floods downstream at the expense of human and material loss.

Historical Hydrological Events

There have been several major flood events in Phú Thọ. In 2019, heavy monsoon rains combined with releases of water from higher up caused widespread flooding in the province. It was reported by the Vietnam Disaster Management Authority that wide croplands were flooded, thousands of residents were displaced, and infrastructure like roads, bridges, and houses were destroyed. The tributaries and the Red River overflowed the banks, impacting economic activities. It is essential to follow up on these incidents to come up with good flood - mitigation programs, improve drainage systems, and render the province resilient to forthcoming hydrological disasters.

3. How is River Flow in Phú Thọ Monitored?

Traditional Methods

Surface Drift Float Method

The surface drift float method is a simple technique of river flow estimation. A floating object, e.g., a buoy or piece of wood, is dropped on the surface of the river. The duration taken by the float to cover a certain distance is recorded, and thus the surface velocity of the river can be calculated. The technique provides only surface-level data, is liable to wind disturbance, and does not provide any information regarding flow at different depths.

Anchored Boat Method (Staff Gauge / Current Meter)

A boat is moored at a location in the river in the anchored boat method. The level of water is recorded by a staff gauge and a current meter is dropped at different levels to measure water velocity. A number of velocity measurements along the cross - section of the river, together with cross - sectional area measurements, permit river discharge determination. Additional data are obtained, but the method is laborious, time - consuming, and dangerous, especially in flowing streams.

ADCP Introduction: Acoustic Doppler Current Profiler (ADCP)

The Acoustic Doppler Current Profiler (ADCP) is a significant innovation in river flow measurement. It is a non-intrusive device using sound waves to measure water velocity at different depths. ADCP has the capacity to deliver continuous flow profiles from surface to river bed at high speed, providing a wider image compared to conventional methods. It enables precision and detailed sampling of data, which is essential for effective water resource management, flood forecasting, and environmental research in Phú Thọ.

4. How Does ADCP Work Based on the Doppler Principle?

An ADCP current profiler operates based on the Doppler principle. It emits sound waves of a specific frequency into the water. The frequency of the echoed waves is altered when the waves encounter moving particles (water molecules, plankton, sediment). If the particles are coming towards the ADCP, the reflected frequency is greater; if receding, lesser. The ADCP measures this Doppler shift very precisely and calculates water velocity at different depths. Several transducers measure velocities in different directions, defining the three - dimensional flow pattern of the river.

5. What is Required for Good Measurement of Phú Thọ River Flow?

Equipment Requirements

To obtain accurate ADCP meter measurements in Phú Thọ rivers, certain equipment features are essential. Material durability is critical due to the aggressive nature of river environments, including pollution, high sedimentation, and varying water levels. ADCPs made from corrosion-resistant materials like stainless steel or titanium are suitable. Compactness and lightweight design enable ease of transport and installation, especially in areas difficult to access. Affordability is also required for extensive application of the technology.

6. How to Choose the Right Current Measuring Instrument?

Deployment Method

• Ship - Borne (Moving Boat) ADCP: Ideal for extensive river surveys, it can measure discharge quickly over long sections and chart flow patterns over different stretches of the Red River and its affluents in Phú Thọ.
• Bottom - Mounted (Fixed) ADCP: Suitable for long - term continuous measurement and can be mounted on the riverbed for logging data over long periods, making possible the examination of long - term flow patterns and seasonal variations.
• Cable - Way ADCP: Where there are cable - way facilities in a section, the technique makes flow measurement at several points possible, which is suitable when boat measurements are difficult.

Working Frequency

• 600 kHz ADCP: Offers a good compromise between range and resolution, with a horizontal range of up to 70 meters, making it suitable for most river sections in Phú Thọ.
• 300 kHz ADCP: With its longer range of up to 110 meters, it would be better suited for deeper and wider river sections, such as in the lower reaches of the Red River.

Brand Recommendations

Few of the world ADCP big brands include Teledyne RDI, Nortek, and SonTek, which offer high-quality and reliable products used in various hydrological study and monitoring programs. As a budget - friendly option, the ADCP manufacturer Chinese company’s "China Sonar Panda ADCP" comes highly recommended. Made of all - titanium alloy, it is more strengthful and reliable and is a suitable option to endure the nasty river condition surrounding Thrissur. As an "affordable ADCP", it boasts decent quality performance at budget price. For more information, visit https://china-sonar.com/.

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