Twin Stream climbing is found on an 800m high buttress of greywacke 20km south of Mount Cook Village. It lies hidden from the road, seven km up Twin Stream amongst a cirque of two and half thousand metre high mountains. The ninety routes are found on the lower few hundred metres of quartz veined slabs, cracks and flakes of greywacke. Most climbs are long multi-pitch traditionally protected routes augmented with bolts and bolted belays.
Twin 60 metre ropes are ideal, for the longest pitches take a rack of 14 extendable draws, up to 10 cams and large selection of nuts and RPs. Even on mostly bolted pitches take trad gear. Belays are usually bolted but take a few metres of 6mm cord or similar and perhaps a few maillons or old carabiners to rig abseils on belays where there are no lower offs or rings on the belay station bolts.
Most newcomers to the area struggle with the long walk in; the keas and katabatic winds that making camping noisy; and finding the correct routes amongst the massive buttress and gullies. This can all be ameliorated by flying in, sleeping in the bivy rocks, and hopefully, by using the photo topos in the new edition of the guide. It’s also a good idea after landing to take a walk up the south side scree slopes to get an idea of the huge scale of the place.
Another tip for a successful trip is to begin on routes like Moon Rise, Moon Struck, Willy Spaniard, Peanut Slab, El Niño/Central Buttress, Centrefire, Aftershock, and Hungry Heart where not only is the climbing excellent but the access, protection and descents are relatively straightforward.
It goes without saying that Twin Stream is a serious mountain crag with all that entails, including the ability to route find, mange loose rock, and self rescue or summon help in the event of an accident. There is patchy phone signal at points on the walk in.
Modern development of Twin Stream began in 1995 with the three pitch route Stealing a March by Andy Macfarlane and John McCartney. It was Andy MacFarlane and Murray Judge who became the two main driving forces of development over the following 6 years. Development has slowed in the last 15 years with only a few routes put up in this time, perhaps reflecting the changing nature of climbing. For those with the time and energy the potential for new routes remains huge, ranging from easy trad climbs to hard technical walls, often hundreds of metres long.
The skiing and winter climbing at Twin Stream is worthy of note. With a fly in and high drop-off excellent ski descents of Mount Dark and Kai Tarau can be had. Steep skiing is found in Shindig Gully and on surrounding couloirs. It is feasible to fly in and ski multiple lines and walk out in a day. Ice does form but not in such quantities as Bush Stream. In the right conditions though, there is much potential for ice and mixed routes.
Access is via the entrance to Twin Stream valley, a 20 minute drive south of Mount Cook Village on the Twizel to Mount Cook road. Flying in and walking out is highly recommended, thus avoiding the 4 hour walk-in that involves 800m gain on indistinct sheep tracks and river bed.
Fortunately, Glentanner Park Helicopter Line is situated a few hundred meters from the start of the walk and as of 2020, up to 5 can fly in for about $330. Ask to be dropped off at the Twin Stream camp site.
If you do decide to walk in, the track starts on the true right of the road bridge across Twin Stream. Occasional red/white markers and cairns mark the way which stays on the true right the whole way. Initially follow the river bed for 10 minutes then follow cairns onto the terrace. A vague track then ascends the left hand spur to reach the higher terrace. Follow sheep tracks and markers through the matagouri until reaching a large eroded gut after 90 minutes. Cross this and again follow markers and indistinct path for a further 30 minutes until cairns mark a 10m decent to the flat river bed. Then boulder hop for a further 1-2 hours, finally reaching the large flat camping area beneath the dramatic Central Buttress.
As an alternative, the river bed has been followed for the whole way thus avoiding the terraces.
The walk out, even if you lose the track, is much easier and takes two and half hours.
An excellent (although difficult to find) rock bivouac can be found at the far end of the meadow, 50m above the flats, on the true left, in the large rocks beneath Central Buttress. There is a flat balcony rock at the entrance. It accommodates 2 comfortably, 3 at a push. There are another two good bivys in the rocks below this, accomodating two in each. Aside from the advantage of not needing to carry a tent, it avoids the katabatic winds and keas that make camping less pleasant. There are multiple other less weather proof rock bivouacs that require a bivy bag.
If camping, the keas will attack unoccupied tents so gear needs to be stashed during the day. Keas are endangered so tolerate their brazenness and don’t feed them. It goes without saying, carry out all rubbish.
Below is a brief guide that can be used in addition to the current guide in the NZ Alpine Club Guide for Barron Saddle to Mount Brewster. A complete guide is in the pipeline. Excuse the childish annotations. Red crosses are a double bolt belay, red circle is a trad belay, green circles are best descent routes- you can rap of anything but these are generally the most straightforward way down. Additional bolts are not always marked - refer to the old guide. If you get up a few of these then you’ll be good to go. Other top picks are March Hare, Once We Were Wasters, Boy Germs, and Fibrillator. If its all too much just got for a nice walk instead.