The Crater Lake Warning Level has reached 3a (on a scale from 1 to 5). The chance of a lahar at this level is unlikely (5-10 per cent), but is an increase from recent years. If the lake continues to rise a lahar becomes likely.
The warning level relates to the height of the Ruapehu Crater Lake with respect to the tephra dam at the outlet to the Whangaehu river. As the crater lake rises, so does the risk of a dam burst, sending a lahar down the Whangaheu river. A lahar would pose a serious threat to any kayakers on the Whangaehu river or nearby streams. If the lahar overtops the protective bund at the head of Waikato Stream, it could also reach the Tongariro river above Rangipo Dam. Kayakers on the Whangaehu and Tongariro should be aware of the lahar hazard.