Victor M. Ponce, Amazon river discharge, Amazon river, Loren McIntyre, annual supply of fresh water  


This letter appeared in South American Explorer, 31, May 1992.


Dear Club:

Loren McIntyre's claim about the flow of the Amazon [Magnum Bunkum, South American Explorer, 30] amounts to the proverbial argument about comparing apples and oranges. Apple: To compare the Amazon's annual supply of fresh water to the total amount of fresh water on Earth, including that held by ice caps and glaciers, ground water, lakes, soil moisture, atmosphere, biota, and rivers. Orange: To compare the Amazon's annual supply of fresh water to the world's annual supply of fresh water that returns to the sea from the land. McIntyre's quote of the article by LaRiviere in Scientific American, 261(3), Sept. 1989, in support of his statement that the Amazon contains less than 1/10000 (0.01%) of the total fresh water on Earth is an apple. The same article states that the World Resources Institute estimates that 41,000 cubic kilometers of fresh water return annually to the sea from the land. UNESCO (Studies and Reports on Hydrology No. 25, 1978) lists the mean annual discharge of the Amazon river at its mouth at 220,000 cubic meters per second, based on a discharge of 157,000 measured at the Obidos narrows. This translates into 6,900 cubic kilometers returned annually to the sea, or roughly 1/6 of the total volume of fresh water returning to the sea. This is an orange. Viewed in this light, there is no popular misconception to correct.


Victor Miguel Ponce