Lakes have a beauty all of their own. They lie lovely, still and quiet, surrounded by the hills or mountains that trapped the water. They do not have the sound of surf or the movement of rivers. A gentle ripple might be seen and heard on a windy day but otherwise nothing disturbs their lonely ancient silence.
Perhaps that is why they have not been in the forefront of discussion of the state of New Zealand's freshwater resources. When we refer to "rivers, lakes and aquifers" we usually have rivers and underground water in mind. But our environment reporter Jamie Morton today draws attention to the particular problems of lake pollution that defy easy or even known solutions.
Rivers and aquifers are quickly flushed and their water quality would soon recover if contaminants from pasture or urban activities are contained. But lakes hold the same water for much longer. Lake Tutira in Hawkes Bay, fed and drained by streams at the same end, takes a decade to replace its water. And the sediments in its bed containing high loads of nitrogen and phosphorus could continue to release those chemicals into the lake water for a century.
The lake is still a beautiful sight for travellers when it appears — suddenly as lakes do — on the route north of Napier. Its shore may still be a popular picnic spot, unless an epidemic of dead fish washes up, as has happened more than once in Morton's report. But signs warn against swimming in the lake and anglers no longer find many of the trout that used to be in abundance there.
Lake Tutira's problems do not have a recent cause. They were apparent by the 1970s, which means they predate the intensified dairy farming that bears most of the blame for the deterioration of rural water courses.
