The Maori view is that wai (water) is the spiritual substance of Papatuanuku-Earth. Over generations, they have found that contaminated water, especially if t contains fecal coliforms cause disease and likely death.
Not knowing anything about microbiology the logical response or the well observed ressonse have always been to see things from a spiritual way, that from te taha wairua. Uncontaminated water had the ability to allow life.
I grew up with grans Wairemana and Rimaha in a remote New Zealand harbour coast. They saw water as waiora or 'life giving.' This was not a casual observation but one tested over generations of sanctions (tapu) and sanctified use (noa).
The first classification they made was that water possessed 'Wairua' or by another name, 'Waiora'. This is the purest form imbued with the spirit to create and nurture life and to counteract evil and sustain well being and safety.
Wai maori is ordinary water with no suspended solids, highly oxygenated special properties excepted with no spiritual significance.
The third classification is Wai unu or drinking water without special properties excepted additives, substance is suspended. Wai kino (dangerous water) or water containing any level of pollution which debase the mauri of water which has been altered with the spiritual component changed and can be harmful; rapids, swirling springs come under this classification.
Waimate is water which has lost its mauri and is dead, damaged or polluted. Water in this category is highly dangerous to the wellbeing of persons. This water has lost its ability to give life. In Maori philosophy, it is almost impossible to restore the mauri ora' to water that has been so affected. Maori know that waiora and wai maori are fundamental to environmental systems and regard any form of water contamination as totally unacceptable. Maori say that waste water must be disposed on land and not in water.
Today as we face global warming, the Maori perspective to water is becoming increasingly relevant. Maori see environmental challenges to include a holistic view where everything is interconnected through whakapapa to Ranginui (Sky) and Papatuanuku (Earth). The cultural landscape has a continuous and cultural extension with natural features such as water catchment, forests, bush, marshlands as well as physical formations such as valleys, estuaries and features that link with kainga, waahi mahinga kai, Parekura, ara, paparahi, waahi tapu not to mention people who live 'back home' on the land (ahi kaa).
Kaitiakitanga is the exercise for the spiritual protection of things precious like water with its potentiality to give life.