How to Measure Water Current of Chari River?

1. Where is Chari River?

The Chari River is a significant river in Central Africa. It flows through Chad and finally into Lake Chad. The river originates in the Central African Republic and flows across a terrain that comprises savannas, floodplains, and areas with a mix of grasslands and sparse woodlands.

The Chari River is a vital resource for the communities along its banks. It provides water for drinking, cooking, and bathing for the local population. The river also supports a significant amount of agricultural activity. Farmers rely on its waters for irrigation, growing crops such as millet, sorghum, and various vegetables. The floodplains are fertile areas that become productive during the wet season when the river overflows.

The Chari River has a strong cultural connection with the people. It is part of their tradition, stories, and even social life. Most festivals and ceremonies are related to it and its flooding and receding times.

2. What is the rate of flow in the Chari River?

The flow rate of the Chari River varies seasonally. Normally, the river is at its highest during the rainy season, which falls between June and September in the region. The river has been recorded to increase its flow tenfold during this period. As the rains fall in the upper catchments, the tributaries result in a rise in the water level. The flow becomes strong enough to carry a great deal of sediment and nutrients. This acts favorably for the agricultural fields downstream, as it improves the soil quality.

During the dry season, this is where the flow rate decreases. The river still maintains its flow, but at much slower rates. Much attention is given to how the water is managed during that period to serve the communities with their basic needs, including the aquatic life that remains. It is, therefore influenced by various factors, which include the rainfall in its catchment area, topography of the river basin that affects water collection and runoff, as well as the water use characteristics of the local people.

3. How to measure water current of Chari River?

There are several methods through which the water current of the Chari River can be measured.

Velocity Meter Method: The conventional techniques involve mechanical or electrical velocity meters. These instruments are deployed in the water at given locations, where the rate of the water's passage can be measured. However, this is expected to need multiple placements in several places and various depths just to determine one characteristic current. Sometimes, it could be so time-consuming, which may even not allow continuous profiling across the entire water column.

ADCP Method: The ADCP current profiler is much more advanced and efficient in water current measurement. It uses sound waves that measure the velocity of the water at different depths simultaneously by emitting acoustic signals and analysis of the Doppler shift of the reflected signals to give a well-structured profile of the current from surface to riverbed. This can make accurate and intensive measures of the water current in various parts of the river.

Buoy Method: In this method, buoys are placed in the river and their movements are tracked over time. The displacement of the buoys due to the water current gives an indication of the speed and direction of the flow. However, this method has limitations. It may not provide accurate velocity measurements at different depths and can be affected by external factors such as wind and waves, which can influence the movement of the buoys.

Among these, the ADCP current meter method is more advanced and suitable for the measurement of water current in the Chari River.

4. Principle of the working of an ADCP using the Doppler principle

ADCPs work on the basis of the Doppler effect. An acoustic signal is sent from an ADCP profiler transducer into the water; the sound waves that result from this interaction with the moving water particles are reflected back to the transducer with a different frequency due to the flow of the water, or so-called Doppler shift.

If the water is moving toward the transducer, the reflected waves will have a higher frequency than the emitted frequency; if it is moving away from it, the frequency will be lower. By precisely measuring this frequency shift at multiple angles and at different depths, the ADCP meter can calculate the velocity of water in various directions and at different levels within the water column. This enables it to create a detailed profile of the water current, thus providing valued information on the speed and direction of the flow from the surface to the riverbed.

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

For high-quality measurement of the Chari River currents, the equipment should be characterized by the following, the reliability of the materials used for its construction for correct and repeated measures; small size, as it is easily thrown into and pulled out of the river, in case access to the place is complicated; the equipment should not be heavy to make the installation work easy and decrease the labor of handling.

The purpose is to make the equipment operate for lengthy periods with a view of minimizing the frequency of battery replacements besides avoiding complicated power supply arrangements. Cost-effectiveness is another important factor since it will facilitate wider usage and applications besides larger-scale measurement campaigns.

In regards to casing, the ADCP flow meter shall be made of Titanium alloy. Titanium alloy has several advantages. It is highly resistant to corrosion, which is very important because the equipment will always be in contact with water that may contain several minerals, sediments, and pollutants. It also has a good strength-to-weight ratio, allowing for a durable yet lightweight casing. It also will be able to resist mechanical stresses during deployment and operation in the flowing water of the Chari River.

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

While selecting the right equipment to measure the current of the Chari River, there are two major factors which need to be considered.

First of all, for horizontal cross - section measurement, depending on the usage purpose, the Horizontal ADCP current profiler (HADCP) is the suitable one. It is designed to accurately measure the flow velocities across a horizontal plane in the river, which is useful for understanding the lateral distribution of the current. In the case of vertical cross-section measurement, the Vertical ADCP is more appropriate since it focuses on profiling the current from the surface to the bottom along a vertical line in the water column.

In contrast, ADCPs of differing frequencies will operate within a suitable water depth. For example, an ADCP current meter working in the frequency of 600 kHz is suitable within the depth of 70 m water. It can ensure relatively shallower parts with exact measurements in current velocity. An operating ADCP at 300 kHz has suitability for deeper water levels, up to 110 meters in fact, which in such a river would certainly offer good applicability within an area showing greater depth.

There are well - known brands of ADCPs such as Teledyne RDI, Nortek, and Sontek. However, for those looking for a cost - effective option with good quality, the China Sonar PandaADCP is highly recommended. It is made of all - titanium alloy material and offers an incredible price - performance ratio. You can find out more about it on its website: https://china-sonar.com/.

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