Reasons for going there
Fortunately we arent so naive as to believe what we see in maps. As we researched the route, every new piece of information revealed a new difficulty without ever making the crossing seem impossible. When we saw the Tunuyán Andean Club photos of people pushing bikes over the Portillo Argentino we became confident that we could do it. But we did not learn of the most serious difficulty until we had committed ourselves.
We realised that we could not undertake the trip without mules. Fortunately the internet is ideal for this sort of thing. At first we tried arranging the trip from Chile by contacting Lo Valdés. Andy there told us of the obstacle to doing so, which is that the Chileans have very strict regulations on the import of livestock. Mules cannot cross the frontier unless they have been fully vaccinated and have the paperwork to prove it. This is difficult and expensive to obtain, with the result that very few mules are able to make border crossings.
It followed that we would have to make do with only partial mule support; and since most of the difficulty is on the Argentinian side, we would have to arrange the crossing from there.
We found the names of a couple of tour organisers in Argentina: Don Rómulo (from both Footprint and Turistel) and Montaña Libre from the Tunuyán website. Both said that they could arrange the mules for us, but Montaña Libre were late in replying, and by then we had already made our arrangements with Don Rómulo. He wanted part payment in advance, and this had to be by Western Union because he doesnt take credit cards. We wired the money after only a brief struggle and set out on our journey before he had time to acknowledge receipt. The total cost for the mules was about £450.
We had not been very precise about what we wanted from the mule support, simply telling Don Rómulo that we had the bikes and 35kg of luggage. The truth is that we didnt know ourselves what support would be needed.
At this point we should mention that we were entirely happy with the service provided by Don Rómulo. He was friendly and solicitous for our wellbeing, making trips into the mountains to judge the snow when the weather turned bad. The arrieros too could not have been better.
The trip had always been on the edge of seeming too difficult, and when we had embarked on it Colin was full of worries that things would turn out badly. His first worry was of being trapped between two passes: in case of heavy snowfall there would be no retreat. Then he became anxious about the final Piuquenes descent: we would be unsupported for this stretch, and if there was any obstacle we would be unable to turn back because of the impassability of the Río Tunuyán. Lazing by the swimming pool in Los Andes he realised for the first time that the Río Yeso was a significant difficulty, and that the Tunuyán Andean Club had felt it advisable to rope up for it. That is something we hadnt taken into account.
When the weather turned bad in the Valle de Uco the concern about snow on the passes re-emerged, together with a new worry about the schedule. But at least we got into the habit of looking at weather forecasts in the newspapers. The crossing is only a few days long, and the forecasts looked far enough ahead to make it seem pretty certain that no new snow would fall, and that there was no danger of being trapped. Don Rómulo was encouraging about the chances of the recent snow melting, but suggested we postpone the trip by a day. Unfortunately Colin rather hastily suggested a telescoping of our schedule. We had planned to cross the Portillo Argentino in one day, have a rest day at Real de la Cruz, and cross the Piuquenes the next day. Colin suggested omitting the rest day. No sooner had this suggestion been accepted than he started worrying that we were committing ourselves to an unrealistic schedule.
We broached the question of the Yeso crossing. At first Don Rómulo and his father suggested that the difficulty was avoidable owing to a bridge presumably knowing of the unfinished one. Then, perhaps having obtained further information, they said that a rope might indeed be a good idea. So we bought one and carried it with us.
When we set off on the journey we found the descent from the Portillo Argentino harder than wed hoped. Our worries about the schedule were reinforced. We said to the arrieros that wed need to spend a night between Real de la Cruz and the Piuquenes pass, and fortunately they didt make any objection.
We worried that even this would not be enough. Assuming an altitude of 3000m for the Yeso valley, the day we crossed the Piuquenes would entail 1000m each of ascent and descent. If in addition the descent required a large amount of double-carrying, then it would be a serious proposition. We therefore drew some illusory assurance from the height of 3500m given by César Pechemiel for the Yeso valley.
The easy walk to El Coletón gave us a breathing space, and the weather behaved as it ought to. The next day we made an early start and found the Piuquenes easier than wed feared; no double-carrying was needed. The Yeso indeed looked a little vigorous when we reached it, but we could afford to wait until the morning, and when we did so it became more sedate. We crossed in it a business-like fashion, and the last of our worries disappeared.
Our technique was to tie the rope once round each of our waists and belay each other as if for a rock climb, using waist belaying. Colin crossed repeatedly until all our belongings were on the other side and then summoned Tracey across. We knew that there were advantages to walking upstream when crossing but did not do so, in part because the best route was at right-angles to the current.
We had 15m of static 11mm rope. We realised at the time that longer would have been better, and that it was needlessly thick. 25m of 7mm tied twice around the waist would have been lighter and more suitable. The knots were the best we could remember or improvise.
It was certainly right that the heavier person should do the repeated carrying. The use of poles is always recommended for river crossings but assumes that the user has two free hands.
If we had known in the UK that we would have to cross a river we would have practised our knots and read up on technique. The latter might have confused us more than helping us. The links page refers to 3 pieces of guidance on the matter, 2 of which peremptorily forbid the use of ropes at all. It seems that there is a risk of being held under water if the rope snags. I felt at the time that the rope was adding materially to our safety, but it is difficult to judge such matters. An informed opinion would be based on knowledge of what happens to people when they loose their footing in fast rivers, and such knowledge is hard to acquire. I therefore feel unable to offer any advice on the topic.
In any case the river was not very deep at the time we crossed it, and in all likelihood would have been perfectly safe with or without a rope but this too is a matter I feel unqualified to judge. Earlier in the season it would have been more dangerous.
Looking back at the route we both feel that it was free from any serious danger or difficulty. At the time, though, we had imperfect knowledge of what was in store for us, and Colin feels that he was a little rash in embarking on it. But we enjoyed it enormously, and commend it to anyone who may contemplate the same route in future.