The emerald Río Manso flows through a wild canyon in Parque Nacional Nahual Huapi (Mapuche for “Tiger Island”) south of the ski resort town of San Carlos de Bariloche, Argentina. The river drains the southeast flank of Monte Tronador (3491 m) (‘Thunderer’ or ‘Anon’ in Mapuche, whose meaning is almost identical to the Spanish), a white behemoth that dominates the skyline. Manso means gentle or calm, but like the Pacific Ocean, the river belies its name.

Its narrow gorge is cloaked in lush vegetation, including impenetrable colihue and quila thickets. Most of the rapids are short, steep technical drops. Hydrologists report December flows of 48 cms that can turn the trip into a scary nightmare. At least one rapid becomes unscoutable, unportagable, and marginally runnable. Mistakes can turn into epics due to the Manso’s remote, mountainous location, which eliminates the feasibility of hiking out. Therefore, paddlers would be well advised to wait until early January, paying close attention to the weather so other plans can be made if the river becomes swollen from rain. For maximum vistas and minimal misery, try to run the Manso on a sunny day. Although the water is warm, a lack of sunlight in the narrow gorge can make for a cold day on the river.

For most mortals, the run begins in a large pool below Cascada de los Alerces elevation 750 meters. In January 1998, Brennan Guth joined local soccer legend Diego Maradona in Bariloche’s “Hall of Fame” after the first successful descent of this 16 m-high waterfall.

A kilometer downstream of Cascada de los Alerces, the calm water ends abruptly at a triple waterfall with the last drop the highest at about 5 m. All three falls are runnable, but if you are hesitant, there is an easy portage over a hill on the left.

Shortly after the triple falls, the river begins to gorge up. Continuing downstream, you will run five rapids in quick succession. Depending on the flow, it may be prudent to portage a sticky, river-wide hole at the end of this sequence. Portage on the left, following a well-trodden, machete-cut trail. Calm water follows, leading into a left-hand bend with rapids. Directly below the bend is a big, marginal waterfall with a tricky entry. Skilled, confident boaters can reasonably run the rapids and the hole, then get out on the left to portage the falls. A route has been cut through the bamboo, but the muddy, wet rock is treacherous. Not that in 2009 the Demshitz crew ran this falls making every drop on the river runnable.

After the above falls/ portage, a major rapid ensues with a large boulder in the center of the river at the bottom. The last class V rapid is the toughest and most difficult to portage. At higher flows, the only eddy is a tiny one at the top on river right. In the past, paddlers have traversed 5 m down the right wall, then downclimbed to the water. After securing a fixed line, boats were hauled down. People used the line for a backup while walking along a treacherous ledge. At lower flows, the rapid is runnable, and the portage much easier. However, there is still only room for one boat at a time in the eddy. If you find yourself on the river at high flows and are unable to eddy out at the top, sneak down between the pillow and rock on the far right. From here, run tight around the left side of the big boulder downstream. Eddy out behind the boulder, then boof into the next eddy directly below. You must avoid a nasty hole that extends from the left to the center of the river.

One more rapid follows before the gorge opens up. From here the whitewater eases to class III as a wall of mountains appear on both sides of the river. Eventually, the river empties into Lago Steffen, named after a German explorer who passed through the area in the 1880s. Hitch a ride on a powerboat or paddle 8 km across the lake to the take-out. Easterly winds help to surf you across the lake. Running the Manso can be a long day, so get an early start.

From Osorno, 913 km south of Santiago, drive east over Paso de Puyehue into Argentina. Drive southeast to the resort town of San Carlos de Bariloche. Continue 35 km to just south of Villa Mascardi. Turn west onto a dirt road towards Cerro Tronador and Los Alerces, and drive 25 km to Cascada de los Alerces. Follow the road to the end, then walk a few hundred meters down the trail to the river.

To reach the take-out, return to the main highway and drive south 22 km past Lago Guillelmo. Turn west on an unmarked road just before the sign Cañadon de la Mosca, and continue 11 km down the road to Lago Steffen elevation 509 meters.

This 16 km stretch (plus 8 km of flatwater across lake) averages 15 mpk or 80 fpm. It is runnable in summer months at rated as follows class  IV+ at  650-800 cfs with 2 portages,  class V- at 800-1300 cfs with two portages,  class V•V+ at any flow over 1300 cFS or  at any flows if you run what most people portage.

Topo maps titled Villa Mascardi

Meandering westward on windswept pampas, the river cuts a swath through the upthrusted foothills of the Argentine Andes. As the river enters a sheer-walled canyon, it constricts dramatically, then explodes at an unrunnable sieve. Although bits and pieces of the drops downstream could be run, it is essentially one long portage on river right. Gaping into the narrows during our portage, we came across a well-surveyed dam site and core sample holes. A runnable class V drop ensues, then another wild cascade. When the canyon walls recede, the river eases to fun, boat-scoutable, class IV+ rapids.

With its occasional class V drop, the river is tough enough to keep the intermediate paddler away, yet quite interesting for an expert. A high water run would test your mettle.

From Palena, 146 km southeast of Chaitén, cross the border, drive through Corcovado, continuing east to Estancia Tekca. You need permission and the key from the ranch managerto drive through a gate (note the following info may be outdated but in 1998 the rnach manager was Helena Höbrich FAX: 0945-9303). Behave yourself while on the ranch, or access to this jewel will be lost. Continue 31 km to Sectional Caridad, check in, then drive through the ranch, and go another 7 km west to the top of the canyon and hike down to river elevation 700 meters..

To find the take-out, drive west 500 m from Corcovado. Turn south towards Río Pico on a good gravel road absent from most road maps. When you reach the bridge spanning Arroyo Poncho Morro, drive down on either side of the creek, where you’ll find serene camping under an immense vault of blue sky at elevation 508 meters. The shuttle is 93 km in length.

This 10 km class IV+•V- run is best in spring and summer months with flows of 800 to 1000 CFS. Expect 3 portages with average gradient of 100 FPM.

Topo maps titled Cerro Caballada, Argentina

Otherwise this river is an almost two hour long non stop class 4+ rollercoaster ride. Really one of the best rivers that Argentina offers. Definitely try to catch in high season.
The photo above was taken on the lower Alumine – a shorter class 3/4 section near the town of Alumine