How to Measure the Water Current of the Kapuas River

1. Where is the Kapuas River?

The Kapuas River is the longest river in Indonesian Borneo. It is found in the province of West Kalimantan, Indonesia. The river has its source in the Muller Mountains and meanders through a vast expanse of rainforests and low - lying wetlands.

The river is an important part of the local ecosystem and economy. It provides an important transport channel for communities living along its banks. Boats and canoes serve as transportation modes for traveling and transporting commodities like produce from farms and forest products. The Kapuas River also supplies water for irrigation, an important element in the cultivation of crops such as rice and palm oil.

The river's ecosystem is extremely diverse. In it, one can find a wide array of fish species, including catfish, carp, and the famous arowana. The monkey, crocodiles, and host of bird species find their homes along its riverbanks. The floodplains and wetlands that come alongside the river play a very key role in ecological balance, providing breeding and feeding grounds for many species.

2. What is the flow rate of the Kapuas River like?

The flow rate of the Kapuas River shows considerable variations in the season and climate. The river's flow is much influenced by Indonesia's climate conditions, particularly the wet and dry seasons. During the wet season, which normally ranges from November to March, heavy rainfall in the catchment area and runoff from the rainforests increase the flow of the river significantly. The river swells and can carry a large volume of water.

While there is a dry season, from April through October, the flow rate would dwindle. It maintains its base flow during this period, which is very crucial for sustaining aquatic life, while also sustaining the livelihood activities of the people through the support of transportation and fishery. The average flow rates can range from a few hundred cubic meters per second in the dry season to several thousand cubic meters per second at the peak of the wet season.

3. How to measure water current of the Kapuas River?

Velocity Meter Method

This traditional method involves the use of a mechanical or electronic velocity meter. Velocity meters are placed at discrete points along a river and directly quantify the local velocity of the flow in that part of the channel. To obtain the average characteristics of water current, it is necessary to measure in several sections of the stream and at several depths. Given the length and the complex, often inaccessible terrain through which the Kapuas River flows, this method can be labor-intensive and time-consuming.

Acoustic Doppler Current Profiler (ADCP) Method

The ADCP current meter offers a more sophisticated and handy means of measuring water currents. It detects the movement of the water particles using sound waves. By transmitting acoustic signals and interpreting the Doppler shift of the signals reflected, it can measure the water velocity at multiple depths all at once. This gives a very detailed profile of the current in the water, thereby helping to give a much more appropriate view of the flow conditions throughout the river. ADCPs could be deployed on boats (given conditions are navigable), bridges (should there be availability), or even sent out on buoys for monitoring continuously.

Buoy Method

The buoy method relies on placing buoys along the river, each equipped with sensors to measure the movement of the water around them. Such buoys float on the surface and can provide some kind of indication about the surface current. However, they may not capture the full complexity of the water current quite as well as the other methods, particularly where understanding the variations in velocity at depth are concerned.

From these methods, the ADCP current profiler is considered a more advanced and practical way of measuring the water current of the Kapuas River.

4. How do ADCPs using the Doppler principle work?

The ADCPs work on the principle of the Doppler effect. When an ADCP flow meter sends an acoustic signal into the water, the sound waves travel through the water and interact with the moving water particles. The frequency of the reflected sound waves changes because water particles are in motion due to the Doppler effect.

If the water particles are moving toward the ADCP, then the frequency of the reflected wave will be higher than the emitted frequency. In contrast, if the water particles are moving away from the ADCP, the frequency of the reflected wave will be lower. By precisely measuring this change in frequency, the ADCP profiler is able to calculate the velocity of the water particles at various depths.

These individual velocity measurements at varied depths are then combined by the ADCP meter to provide a complete profile of the water current. This therefore, enables a detail in understanding how the water is flowing not only at the surface but right through the vertical section of the river.

5. What's needed for high - quality measurement of the Kapuas river currents?

To measure the currents of the Kapuas River with superior quality, the equipment has to contain certain characteristics.

The material reliability of the equipment should be high. The equipment is supposed to be exposed to harsh conditions in the river environment, including exposure to water and sediment, or extreme changes in temperature. The flow in the Kapuas River is variable; thus, the equipment should be durable to stand the force during its high flow or when there is debris such as logs and branches.

A small size, light weight, and low power consumption are desirable. A compact and lightweight device is easy to handle and deploy, especially in the remote and often hostile conditions of the rainforest environment. Low power consumption means that the equipment can operate for extended periods without the need for frequent battery replacements or access to a continuous power source.

Cost-effectiveness is a major factor. The lower the cost, the greater the application of measurement tools can be distributed, in order to monitor more places in the river.

Regarding the casing of the ADCP flow meter, the use of a titanium alloy is highly suitable. The reasons include the following, it is highly resistant to corrosion, which is very important when working with water bodies like the Kapuas River, where the equipment will always be in contact with water and potentially corrosive substances. The material is also strong and durable, able to resist physical impacts and pressure changes that may occur during deployment and operation. Besides, titanium alloy has a relatively low density that will contribute to the overall goal of keeping equipment lightweight.

6. How to Choose the right equipment for current measurement?

When choosing the right equipment to measure the Kapuas River current, one needs to consider several factors.

Based on the Purpose of Use

A horizontal ADCP current profiler (HADCP) would be what one needs if the intention is toward measuring the horizontal cross-section of the river current. HADCPs are better equipped to provide more accurate results in respect of water flow in the horizontal plane, which is useful for assessing the overall movement of water across a particular section of the river.

If the concern is to measure the river current's vertical cross-section, then a vertical ADCP current meter should be chosen. The velocity of the water can be measured with great accuracy at different depths with the help of vertical ADCPs. These would provide a very detailed profile of how the water is flowing vertically within the river.

Based on Frequency

It depends on the depth of the water in the Kapuas River, but usually, a frequency of 600 kHz is quite suitable for water up to 70 meters deep. The 600 kHz provides good resolution and decent accuracy for measuring the water current in a relatively shallower water.

The 300 kHz ADCP is suitable for deeper waters that go beyond 70 meters up to approximately 110 meters. The lower frequency of 300 kHz is more able to travel more deeply through water and still yield reliable water current measurements.

There are well-known ADCP brands: Teledyne RDI, Nortek, and Sontek. However, for those seeking a cost - effective option with excellent quality, the China Sonar PandaADCP is worth considering. It is made of all - titanium alloy material, ensuring durability and reliability. With its remarkable cost - performance ratio, it provides a great alternative for measuring the water current of the Kapuas River. You can find more information about it on its official website: https://china-sonar.com/.

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