How to Measure Water Current of the Jubba River?

1. Where does the Jubba River flow?

The Jubba River is one of the principal watercourses in the Horn of Africa. It originates in the Ethiopian Highlands, where a set of small tributaries are gathered together and gradually unite to form the main stream.

It passes through Somalia, playing the role of being a lifeline for humans and other ecosystems southwards. It cuts through arid plains and semi-arid lands where access to water is a challenge.

The river is punctuated with small villages and towns, with the local communities largely reliant on the Jubba River: a meaningful source of water whereby it is used for drinking, irrigation of farmlands, and watering livestock. Fishing is also an important activity along the river, providing a source of food and livelihood for many.

The Jubba River is not only a lifeline for human activities but also hosts myriad wildlife. Fish species are in plenty in this river, while floodplains and wetlands along its course are habitats to several species of birds, mammals, and reptiles. The river itself and surrounding areas form part of a very important ecological corridor within the arid region.

2. What is the Flow Rate of the Jubba River Like?

Jubba River stream flow is highly erratic, seasonal, and dependent on rainfall distribution. Within the usual rainy season between April and June of each year, there is increased flow in this river. During the rains at the Ethiopian Highlands and catchment areas around, waters run down towards Jubba River, promoting a relatively high flow rate.

This period of high discharge is very important in renewing the volume of water in this river, filling any reservoir that might be present, and keeping downstream ecosystems healthy. It also helps in the downstream transportation of sediments and nutrients, very important for floodplains' fertility.

This is because during the dry period, which could last for about six months of the year, Jubba records a vastly reduced flow rate. Sometimes, the course might be completely dry, with only isolated water pools in some areas. The average flow rate could be between a few hundreds of cubic meters per second during the peak period of the rainy season to barely a trickle or zero during the dry season.

Another aspect is that the volume of water carried by the Jubba River affects transportation and trade along its banks. In high-flow periods, small boats and canoes can manage more easily in the river to move people and goods.

3. How to Measure Water Current of the Jubba River?

There are a number of ways one may measure the water current of the Jubba River:

Velocity Meter Method

The traditional methods involve the use of mechanical or electrical velocity meters. These are usually placed at certain points within the river and allow for the actual measurement of the speed of the water movement from those specific discrete points. However, this requires great attention with regard to placement and multiple measurements at different depths and positions so that comprehensiveness can be achieved regarding the overall current of the water. Indeed, it is rather time-consuming and labor-intensive, especially in attempting to measure across a big stretch of the river.

Acoustic Doppler Velocity Profiler (ADVP) Method

More sophisticatedly and handily, the current can be measured by ADCP profiler. It basically works with sound waves that detect the moving water particles. By emitting an acoustic signal and analyzing the reflected signal for Doppler shift, it can measure the water's velocity at several depths simultaneously. This gives a very accurate profile of the water current and thus allows one to make a more poignant judgment about the flow conditions across the entire width of the river. ADCP meter could be installed on boats, bridges, or even deployed on buoys for continuous monitoring.

Buoy Method

The buoy method is based on placing buoys in the river that will carry sensors which can measure the flow of movement around them. The buoys can be floating on the surface, mostly providing partial indications of the surface current. Indeed, the characteristics of the water current would be less precise compared to the rest of the methods here presented, with variations of velocity in the different depths.

Among the many means, the ADCP flow meter has proven to be one of the most efficient and effective means for taking the water current measurement of Jubba River.

4. How are Doppler Principle ADCPs Work?

The ADCP current profiler work on the principle of the Doppler effect. During operation, an acoustic signal transmitted by the acoustic doppler flow meter travels through water and scatters back from the moving water particles. The reflected sound waves return with a different frequency, since water is in motion, because of the Doppler effect.

If the water particles are moving toward the ADCP current meter, then the frequency of the reflected wave will be higher than that emitted. Conversely, if the water particles are moving away from the ADCP, the frequency of the reflected wave will be lower. By precisely measuring this shift in frequency, the ADCP can calculate the speed of the water particles at different depths.

These are individual velocity measurements at different depths, which the ADCP combines to give a full profile of the water current. It thus allows for detailed understanding of how the water is moving not only at the surface but throughout the vertical section of the river.

5. What is Required to Have Good Quality Measurement in Jubba River Currents?

In the development of high-quality measurements of currents of Jubba River, several issues are considered critical in terms of equipment.

The first one relates to the fact that the equipment has to be highly material reliable; it is supposed to resist severe river environmental conditions, which include being in contact with water and sediment, and also variations in temperature.

The second ones would include small size, lightweight, and low power consumption. The smaller and lighter it would be, the easier it would be to handle and launch either on a boat or attached to a buoy. Low power consumption means equipment could operate for extended periods without the need for frequent battery replacement or access to a continuous power source.

Another critical issue is cost. The lower the cost, the more the measurement equipment can be spread down the river, thus enabling detailed monitoring of the same.

In as far as casings for the acoustic doppler velocity meteris concerned, the best choice for its construction is the titanium alloy. The advantages of titanium alloy include:. It is very resistant to corrosion, which will be important when the equipment deals with water bodies like the Jubba River, where the equipment might be constantly in contact with water or any other substance that causes corrosion. The material is strong, durable, and may resist physical impacts and changes in pressure during deployment and operation. In addition, titanium alloy has a relatively low density to make a contribution to the general purpose of keeping the equipment lightweight.

6. How to Choose the Right Equipment for Current Measurement?

Selection of proper equipment for measurement of Jubba River's current is guided by a number of factors.

Based on Purpose of Use

In cases where the intention is horizontal cross-section measurement of river current, an ADCP should be of the HADCP type. HADCPs are meant for offering accurate measurements in the horizontal plane of water flow whereby the overall movement of water across a section is of utmost importance.

On the other hand, if the vertical cross-section of the river current is to be measured, a vertical ADCP would be suitable. The vertical ADCPs have the capability to provide the exact measurement of the water velocity at variable depth, hence providing the profile in detail of how the water is flowing vertically within the river.

Based on the Frequency

Frequency also depends on the water depth of the Jubba River; normally, a 600 kHz ADCP will be appropriate for water depths up to 70 meters. Working with the 600 kHz frequency allows for good resolution to be achieved and for an accurate measurement of the water current in relatively shallow waters.

More appropriately, such as deeper waters exceeding 70 m and approximately up to 110 m, the frequency of an ADCP should be a 300 kHz. The much lower frequency of 300 kHz therefore easily travels down further into the water and still allows more reliable measurements with respect to the water current.

There are several well-known ADCP brands in the market, including Teledyne RDI, Nortek, and Sontek. But to others who want more economical yet quality devices, they can check the China Sonar PandaADCP. It is also all-titanium alloy material integrated that will give much durability and reliability to whoever will use it. With its excellent performance-cost ratio, it serves as an alternative in measuring Jubba's water current. Please check their official website at https://china-sonar.com/.

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