Distance: 2.6 km (1.8 DOC hours) - Unmarked route, clear - Moderate-hard terrain
Altitude: 932m to 1078m. Gain: 245m. Loss: 265m . Gradient: 11 deg (Moderate)
Skills:

Unmarked route, clear (7/9)
Unmarked route, follows obvious geography (river, spur, trail, etc)

Secondary, unmapped (4/5)
Route not on maps, an alternative recognised access to hut or along range / catchment

Moderate (difficulty: 3/5)
Occasional moderate climbs

Moderate-hard (difficulty: 4/5)
Tall, walkable scrub / large rocks, occasional waterfalls or gorges in rivers

None (difficulty: 1/7)
No alpine skills required

None (difficulty: 1/6)
No unbridged river crossings

None (difficulty: 1/7)
No alpine skills required

Below the bush line so not likely to be too difficult mid winter.

From the water tank, head South down the hollow past the radio aerials and solar panels keeping to the Western side.. Keep an eye out for an exit up onto the ridge out of the hollow - there was a bit of playground matting in the soft ground just as the track climbs out.
Follow the ridge up onto Oriwa. Then drop down the South side and along to the saddle between Oriwa and 985 has a couple of steepish sections but is generally easy. There are a few twists and turns and the ridge becomes obvious and sharp, then broadens. The ridge climbs up onto 985 and feels like it turns hard to the left to wander along to Notoriwa.

Note: Described in the reverse direction to your journey

Follow the ridge North, At 985, the ridge feels like it swings to the East a bit. There is a steepish climb up out of the saddle between 985 and Oriwa.
From Oriwa, it's a short drop down to the Hollow. Keep an eye out for an obvious trail entering the hollow and follow this along to the water tank. Good camping in th etrees on the Eastern side of the hollow.