How many rivers are there in the Andes?

Stephen_BBC

Hello,

I am doing some research for a new wildlife series all about the incredible wildlife and ecosystem of the Andes. We aim to shine a light on the animals and landscapes which make this part of the world so special including how important its rivers are!

I read on the UN Academy website that “According to the United States Geological Survey, there are over three million rivers in the world. However, this number includes all streams, creeks, and brooks, not just rivers.”

We’re trying to find an estimate for how many rivers there are across the entire Andes range. It has been rightly pointed out that I should define my parameters for “what is a river?” and “what is the area of the Andes range” so I’ve tried to do so below!

“River” - It seems logical to use HydroSheds parameters for a “river” – “HydroRivers and HydroATLAS applications “represent a vectorized line network of all global rivers that have a catchment area of at least 10 km² or an average river flow of at least 0.1 m³/sec, or both.”

“Andes mountains” – We’re after the best estimate we can get, so happy to go along with a more accurate definition if you use different parameters but we’ve been working off the following basis. “the Andes mountains range about 4,500 miles (7,242 kilometers) long. The mountain range spans seven countries — Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina — and can be found between 10 degrees north and 57 degrees south latitudes and 70 degrees to 80 degrees west longitude. It is up to 500 miles (804 km) wide.”

We’d also be happy to get an estimate for the Andes using the same parameters as the “over three million rivers in the world” stat i.e. including all streams, creeks and brooks, not just river, as mentioned above.

Many thanks in advance for any help you can offer and look forward to hearing from you!

Kind regards,
Stephen

Aaron2023

Hi Stephen,

Thank you for the fun question. I have done some analyses and counted 123,029 rivers in the Andes. To arrive at this number, I used the global Free Flowing Rivers (FFR) river network, a related HydroSHEDS product, created by Grill et al. (2019). The FFR river network uses the same discharge and catchment area criteria as HydroSHEDS to define a river. To define the Andes, I used an ecoregion classification dataset that showed good agreement with topographic data and the definition you provided. To offer a comparison between the number of rivers in the Andes and at the global scale, I also counted the total number of rivers in the global FFR river network, which was 4,368,233.

Best regards,

Aaron

References:

Grill, G., Lehner, B., Thieme, M., Geenen, B., Tickner, D., Antonelli, F., Babu, S., Borrelli, P., Cheng, L., Crochetiere, H., Ehalt Macedo, H., Filgueiras, R., Goichot, M., Higgins, J., Hogan, Z., Lip, B., McClain, M.E., Meng, J., Mulligan, M., Nilsson, C., Olden, J.D., Opperman, J.J., Petry, P., Reidy Liermann, C., Saenz, L., Salinas-Rodriguez, S., Schelle, P., Schmitt, R.J.P., Snider, J., Tan, F., Tockner, K., Valdujo, P.H., van Soesbergen, A., Zarfl, C. (2019) Mapping the world’s free-flowing rivers. Nature 569, 215-221.

Stephen_BBC

Hi Aaron,

Thanks so much for your help and expertise! That is an amazing stat which will no doubt excite and inspire our audiences to appreciate just how important The Americas and the rest of the world’s rivers are!

Best regards,
Stephen