ADCPs™ Assist International Team to Measure the Mightiest River:
Measuring the Amazin' Amazon

Scientists on the Amazon found ADCPs™ to be far superior equipment, method and logistics for producing more accurate measurements of river discharge.

ADCPs™ have sparked a revolution in measuring river dischargethe volume of water flowing in a river. The ADCP™ method replaces a labor-intensive, time-consuming, life-risking approach that has remained largely unchanged for a hundred years. Nowhere are the advantages of the ADCP™ method and logistics more dramatic than the Amazon River in Brazil.

Since 1994, an international team under the aegis of Dr. Jean-Loup Guyot of France's Institut de Recherche has been using the ADCP™ to study river discharge throughout the Amazon basin. The team is comprised of Brazilian (ANEEL, formerly DNAEE) and French (IRD, formerly ORSTOM) workers. They have taken more than 500 sections, not only at traditional sections but at new and interesting sites. Through this period, the project organizers have been ably supported by Teledyne RDI's exclusive representative in Brazil, Mr. Herbert Fortes of GEOTRON.

The red-brown Solimoes (left) merges with the black Rio Negro on the right at the birth of the Amazon.

At Manaus 99, an international symposium in Brazil last November, many of the team presented papers describing their ADCP™ work and results. We learned that across sections several kilometers wide (and 1500 km from the Amazon mouth) the ADCP™ recorded speeds of 1.5 m/s and discharges of 150000 m³. Together with a 5-6 m drop in water level, discharge sinks to one third that volume in the dry season though fast currents persist. We learned that ADCPs™ removed the need for echo sounders to measure the cross sectional area of the discharge section. Also we learned that field programs measuring sediment flux are guided by the ADCP™'s visual display of echo intensity for more informed collection of water samples.

Particularly interesting ADCP™ data were included in the report by Alain Laraque of IRD and his co-authors. The focus of the work was the confluence near Manaus of two dissimilar rivers to form the Amazon. The ADCP™ data at the confluence are stunning. Taken from Alain's report, we show here two TRANSECT screens that vividly describe the contrasting yet preserved character of the two rivers after they merge to form the mightiest river on the planet. Comparing similar regions in the two displays, you can see the power of the ADCP™ data set for river research. The red-brown Solimoes is a wide, fast, sediment-laden river that merges with the black tannin-rich Rio Negro, which is a wide, slow river devoid of suspended sediment. At this fascinating site, named Encontro Das Aquas (Meeting of the Waters), the rivers flow side-by-side for a couple of kilometers steadfastly preserving their contrasting colors and properties across a very sharp interface. Ultimately entropy prevails and by 10 km downstream the visible contrast has disappeared.

The two merging rivers have much different water velocities	... and much different suspended material.

Thrilled with the quality and amount of data collected with the Teledyne RDI ADCP™, Dr. Laraque told us, "For the hydrologists, the use of the ADCP™ is a revolution of the same magnitude as the discovery of the microscope for biologists."