By Monica Evans RAGLAN, Aotearoa New Zealand — The wide, steep-cliffed Whānganui River ferries spring water and snowmelt from Mount Tongariro to the west coast of Aotearoa New Zealand’s North Island. Tracing its length by waka (Māori canoe), the steady surge of deep-green, mist-trimmed freshwater invokes a powerful presence. For local iwi (Māori tribes), that presence is especially significant: Whanganui River is considered a literal, sentient ancestor who can be spoken and listened to. Damage to the watershed, such as pollution from agriculture and forestry and the construction of hydropower …