Mike Chapman: Water storage to improve water standards

Mike Chapman

Environment Minister David Parker has announced that preliminary work has begun to create a new freshwater policy for New Zealand, building on the previous Government's work.

He is quoted in media as saying: "I think [most] New Zealanders share an objective that their waterways should be clean enough to swim in summer and there should be enough water left in the river to swim in." The media report notes that the most polluted rivers are urban rivers.

The question is, what causes the most pollution in our rural rivers? Pollution is intensified during floods by heavy rain, especially where river flows dramatically increase and with it, runoff and drainage from farmlands and roads.

While you can't necessarily collect water during times of peak flooding as it is too dirty, you can collect water at times of high flow, for example, during winter.

To keep river flows consistent and ensure enough water for swimming in summer, one of the solutions is to capture and store abundant water during winter and not let it run out to sea.

The advantage of storing water in a dam is that it can then be used to keep river and stream flows running during dry periods. So water storage will give the minister what he wants: cleaner waterways and consistent river flows during dry periods.

Water storage is also important to sustainability of supply during times of drought, enabling fruit and vegetable growers to keep producing food for the domestic and export markets, with the use of irrigation.

Irrigation is a controlled application of water and when used properly, does not cause river and stream pollution. Run-off is costly and defeats the purpose of irrigating.

My final point is that there is enormous potential for more water storage across New Zealand, greatly assisting the Government's drive for clean rivers and streams.

According to Niwa, 80 per cent of our rainfall goes out to sea, 18 per cent evaporates and just 2 per cent is used for irrigation.

As a country, we can do a lot more through water storage to help clean up our rivers and streams, as well as to ensure crop and pasture survival and to provide drinking water for plants, animals and humans.

So we will be advocating that as part of the new freshwater policy, water storage is one of the key ingredients that provides not only environmental sustainability, but also ensures financial sustainability for not only our rural communities, but all of New Zealand.

Mike Chapman is CEO of Horticulture New Zealand. This is his blog in Horticulture New Zealand's latest newsletter (www.hortnz.co.nz).
Views expressed here are the writer's opinion and not the newspaper's. Email: editor@hbtoday.co.nz.