Río Marañón water levels: Grand Canyon of the Amazon

WATER LEVELS ON RÍO MARAÑÓN

Río Marañon starts fairly small at the start of the Upper Grand Canyon section but by the time it enters the jungle it is a river ~3X as big as the Colorado through Grand Canyon. Average annual discharge at Balsas is a bit higher than the Colorado River through Grand Canyon (see comparison below). Average flows at other points are listed below in the table for both a dry-season month (July) and the highest wet-season month (March). The graphs show average river levels and actual recorded levels at Balsas. May is the start of the dry season and the river is generally at medium levels and dropping steadily. From October through April, there will likely be rain some days in the main canyon and water levels will generally be fluctuating. Flood flows have be experienced mid-October through mid-April, but are most common Dec-Apr. Note the river at Balsas most years peaks around 1500-2500 cms (53000-87000 cfs) several times between Nov-Apr, but is more typically 500-900 cms (18000-32000 cfs) during these months.

The river is runnable all year long and never gets too low. In fact, most previous descents have been at low levels Jun-Sep, which has the advantage of stable clear flows, more and larger beach camps, more smaller drops, and less chance of rain. In the rainy season (Oct-Apr), the river is usually muddy, there are bigger raft-flipping hydraulics, some rapids become very long, and potential rising river levels may mandate moving camps to higher ground at times. The Inner Gorge section is best avoided at high water due to the danger posed by the class Vs. However, the river from Chagual down is an excellent run even at high flows with numerous big Grand Canyon style rapids of class III and IV difficulty.

river Ene Feb Mar Abr May Jun Jul Ago Sep Oct Nov Dic Avg
Marañon (at Balsas) cms 640 920 980 870 410 210 140 130 140 240 450 580 475
cfs 22800 32700 34700 30600 14700 7500 5000 4600 5000 8400 16200 21400 17000
---------------------------- ----- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- -------- --------
Colorado (LeesFerry) cms 148 188 259 560 1188 1476 597 293 234 234 175 163 486
[pre-dam flows 1922-1962] cfs 5300 6700 9200 19900 42200 52400 21200 10400 8300 8300 7500 5800 16480

If 16480 cfs average for the Colorado River sounds high, that's because it is pre-dam flows. After Glen Canyon Dam, Colorado River flows have averaged only 14200 cfs, presumably due to decreases from filling the reservoir and from evaporation.
km location elevation avg. flow July avg. flow March difficulty
0 Puchka 2130 m 70 cms (2400 cfs) 350 cms (12000 cfs) IV (V) [to Chagual]
206 Chagual 1230 m 120 cms (4000 cfs) 600 cms (21000 cfs) II-III (IV) [to Balsas]
357 Balsas 850 m 140 cms (5100 cfs) 980 cms (34700 cfs) III-IV [to CorralQ.]
542 CorralQ. 390 m 250 cms (8000 cfs) 1200 cms (41000 cfs) II [to Rentema]
600 Rentema 380 m 600 cms (21000 cfs) 2200 cms (77000 cfs) III-IV [to Nieva]
788 Nieva 200 m 2000 cms (70000 cfs) 4000 cms (140000 cfs) II-III [to Sarameriza]
872 Sarameriza 140 m 3500 cms (120000 cfs) 6000 cms (210000 cfs) flat [to Iquitos]