ADCP Use for Flood Management of the Içá (Putumayo) River

1. Where is the Içá (Putumayo) River

The Içá or Putumayo River originates from South America. It has its flow through Colombia to Brazil, and forms a very crucial part of the Amazon River Basin. It meanders through dense rainforests and traverses areas boasting a rich biodiversity.

It traverses several small indigenous communities and settlements on its course. In the matter of pluviometric regime, the region that surrounds the Içá (Putumayo) River represents a tropical climate with superabundant rains in every season of the year; the rainy season has much heavier downpours and contributes a lot to the river's water volume. This river acts as an important source of water for local people, serving not only for fishing and other water-based activities but also serving a greater purpose in maintaining ecological balance for the surrounding rain forests.

2. What are the causes of flood events in the Içá (Putumayo) River?

Mainly, the Içá (Putumayo) River floods result from great and uninterrupted rainfall, as it constitutes an area of tropical climate. When the rains become higher than the regular carrying capacity of the water in this river, it starts to raise the level of water very quickly.

The flat topography of large areas of its floodplain is another helpful factor for this process of flooding. Thus, such open and low places can spread easily. In addition, the top reaches of the river basin are experiencing deforestation; although efforts to combat it have started, it cannot be disregarded. The ability of the land to absorb water becomes reduced, therefore increasing the surface runoff, which adds to higher water volumes reaching the river. Given the complexity of these flood-causing factors and the need to manage the river's behavior during such events, Acoustic Doppler Current Profiler (ADCP) offers a more advanced and efficient means of measuring and understanding the river's flow.

3. How do ADCPs using the principle of Doppler work?

ADCPs work on the principle of the Doppler effect. ADCPs emit an acoustic signal into the water. Because of the Doppler effect, the frequency of the reflected waves changes as it scatters back from moving water particles.

Different transducers located on the ADCP current meter serve to send and receive the acoustic signals in different directions. This would yield, from the very precise measurement of the frequency shift between the emitted and the received signals, the velocity at every depth and across the cross-sectional area of flow of water in the river. For instance, it could measure the flow velocity from the bed to the water surface and across different widths of the Içá (Putumayo) River, providing full details on the water flow in the river.

4. What are the applications of ADCP in floods of the Içá (Putumayo) River?

Flow Velocity Measurement: The ADCP current profiler is able to measure the flow velocity of the Içá (Putumayo) River during flood periods. This will be important in determining the speed at which water flows through various sections of the river. By monitoring flow velocity closely, it can indicate where the water is either speeding up or slowing down, which might tell something about the progress of the flood and possible impacts. In some cases, such areas can be near the riverbanks or in the main channel.

The application of the measurement will be flow rate: the flow rate is computed by multiplying the measured flow velocity by the cross-sectional area of the river. In the case of flooding of the Içá (Putumayo) River, for example, this information becomes relevant to the computation of the total volume of water passing through a certain section per unit time. This helps in predicting the overall magnitude of the flood and its potential downstream effects, which is vital for flood forecasting and preparedness.

Sediment-Transport Research: The Içá (Putumayo) River carries a great load during flooding. ADCP flow meter can detect the movement of sediment particles by analyzing the backscattered acoustic signal. This will provide a great deal of important information on sediment transport studies during flood events, which is considered crucial in the understanding of long-term changes within the riverbed and overall health of the river ecosystem.

5. How does the data measured by ADCP contribute to the flood warning and risk management of the Içá (Putumayo) River?

Flood Warning Aspect

• Flow-velocity and Flow-rate Data Monitoring: The ADCP profiler enables the continuous monitoring of flow velocity and flow rate to detect abnormal changes. If the flow velocity is over a threshold or the flow rate shows a sudden increase, it can trigger an early flood warning. Further information will be forwarded to local authorities, emergency response teams, and communities located near the river.
• Water-Level Prediction and Warning: The flow data obtained from ADCP can be integrated with other hydrological models to predict water level changes. By analyzing the relationship between flow rate and water level, more accurate flood warnings can be issued, especially in flood-prone areas along the Içá (Putumayo) River.

Risk Management Aspect

• Water - conservancy Project-dispatching Decision Support: The accurate flow data provided by ADCP meter is invaluable for the operation and decision-making regarding water conservancy projects like dams and reservoirs on the Içá (Putumayo) River. Decisions about water release or storage can be made more effectively to mitigate flood risks downstream.
• Flood-disaster Assessment and Emergency Response: In case of any flooding, the data measured by an ADCP would be applied in assessing the area affected by the flood and its impact. This is useful in formulating appropriate emergency response activities, such as the organization of rescue operations, damage assessment surveys, among other activities.

6. What's needed for high-quality measurement of Içá (Putumayo) River currents?

For high-quality measurement of the Içá (Putumayo) River currents, several aspects are crucial with respect to the measuring equipment. First, the material of the equipment should be reliable; it needs to bear the harsh aquatic environment of the Içá (Putumayo) River, including potential corrosion from the water, impacts from floating debris, and the abrasive effects of sediment.

A smaller size and lighter weight are desirable features in view of the installation and deployment of the equipment at various locations along the river. The power consumption should be low to ensure continuity in case power supply is limited or unstable at the site. Cost-effectiveness is another important consideration factor, as large-scale deployment may be necessary to monitor the currents of the river comprehensively.

The casing of ADCP will be of titanium alloy. For this purpose, Titanium alloy is a good choice, having excellent corrosion resistance for sustaining the chemical and physical action of Içá (Putumayo) River water. It will provide a good strength-to-weight ratio, which will make equipment durable and easy to handle at the time of its installation and maintenance.

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

The equipment selection for current measurement at Içá (Putumayo) River depends on the purpose of measurement. For horizontal cross-section measurement, HADCP would be suitable because it gives detailed flow velocity information across the width of the river. For vertical cross-section measurement, a Vertical ADCP would be more appropriate for measuring the flow velocity distribution from the riverbed to the water surface.

Frequency of ADCP: For the Içá (Putumayo) River with a relatively shallow part-for instance, less than 70m of water depth-the 600kHz ADCP can give quite accurate results. A 300kHz ADCP will be more suitable in areas with a depth of about 110m.

Presently, there are several ADCP brands on the market; these include Teledyne RDI, Nortek, and Sontek. However, a recommended Chinese brand is China Sonar PandaADCP. It has an all-titanium alloy material and provides excellent performance with an impressive cost-effectiveness ratio. You may visit its website at https://china-sonar.com/.

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