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.