"The farmers I work with love their land and the water that runs through it. They really, really, want to do the right thing – I have not worked with a farmer who doesn't."
She says it's not easy for farmers who don't always have the resources to farm the land as impeccably as they would like – and have to make some tough decisions about allocation of those resources.
What we are seeing is the result of 150 years of some poor land management in New Zealand, Lees says "Removing forests [for building houses in cities as well as for farming] caused sediment to flow into rivers and lakes. The nitrates and nitrogen challenge is complex and will be very costly to fix – but this all needs to be seen in perspective.
"Who was it who benefitted from this; who stood by and permitted or encouraged our agricultural land to be enriched? Whose economy improved because of it? We were all participants in what took place over those 150 years.
"We used to love things like aerial topdressing and bush burning. We benefitted as a nation with our economic growth and we are all complicit – that's how people should be looking at the water quality challenge."
Lees says while rural waterways are often the focus, cities often provide the worst pollution. In Auckland and other cities there is stormwater contamination with sewerage, toxins running off roofs, chemicals and industrial waste and harmful substances washing off roads – all running into urban waterways which feed into the harbours.
Auckland had introduced targeted rates for the natural environment to increase protection of natural resources like waterways – "it's a great thing but you still perceive a sense of complaint from some about having to pay those rates to help fix things up."
It is, she says, mindsets that need to change. Growing up in Whakatane in the 1960s, Lees was a member of a family unusually (for the times) concerned about the environmental impact of clearing forest and bush and industrial waste going into the Whakatane River.
"The river wasn't clean at all but all you got in those days was a sense of 'that's how it is' – and the legacy of those things and many, many others is still with us. We all stood by and let it happen and the whole nation benefitted from it.
"Now it's time for all of us to help fix it. It's not easy – things like nitrate and nitrogen are complex problems. Most people don't realise that the waters I swam in to write my book aren't today's water – it's water from our great-grandparents' days."
That can be how long – up to 100 years or more, she says – it takes for water absorbed by the land to reach aquifers and then return to the surface.
While a sense of ownership across the community at large was needed, Lees says the main point of a "fundamental re-think" is to reconsider our relationship to the natural world.
There are some places in New Zealand less suited for dairying, she says, where the soils, landscapes or aquifer systems are simply too sensitive to support a long-term dairy platform with historical nitrate-nitrogen loads. Fencing and riparian planting alone won't be enough in these areas and Lees says farmers have "a critical role in ensuring their operations do not overstock and overload the ecological systems that keep our waterways healthy".
Lees' childhood near Whakatane saw her swimming in a local creek, spawning a lifelong love of swimming outdoors. As an adult, with her kids at the beach one day, she realised she had submerged her love of swimming and swore she'd swim every day that summer – which then morphed into every day for a year and then a decision to write a book about it.
Her work travels took her to different waterways round the country and she began interviewing other committed outdoor swimmers, discovering what a huge part of the Kiwi culture was embedded in our rivers, lakes, ponds, estuaries, wetlands and springs.
She swam even in winter and, when she'd been delayed by work or other distractions, at night and in the rain: "I love swimming in cold water. You get that wonderful glow that lasts for hours and a sense of freshness that gets inside you."
Not all of the waterways she swam in were "the cleanest" but they were all loved by their local communities.
"It's essential we clean up our waterways," she says, "even though it is a complex problem and it will take a fundamental re-think of the way we think about and treat the natural world."
