By Malcolm Campbell.
On our Waihi property we have a wetland in the vicinity of 1.5 Ha or just under four acres. Generally it is a broad horseshoe shape and exact measurements are difficult. Most of the water is 1 to 1.2 metres deep with one area close to 3 metres deep. The water in the pond comes from a catchment on the farm of around 60 Ha and in heavy rain an amazing amount of water pours off that 60 Ha. The main outlet has a concreted open spillway which flows in varying amounts in most months of the year. Flow does cease in longer dry periods such as in 2020. There is also a second spillway 7 metres wide and set 300mm, a foot or so higher than the main concreted outlet. This grassed outlet has flowed up to knee-deep four times since the pond was set up in 2006. The Coromandel Peninsula can get exceptionally heavy rain at times, hence the second overflow outlet. As the water comes only from our farm catchment it provides an excellent opportunity to analyse all the properties of the water. We have sent samples of the water to Hill Laboratories in Hamilton.
To provide a comparison, test samples were also taken from the Ohinemuri River. The samples from the Ohinemuri were taken from three locations - before the river passed through the town; after the town; and again after the outlet from the town treatment ponds. We can release these results shortly. The main difference is that no herbicides or nitrogen is used on our property while the Waikato Regional Council has an annual spraying programme directly into the Aquatic Environment, hence the disappearance of the trout. People could fish for trout in that river but that has all stopped. There are no trout.
The test samples have remained remarkably consistent from our pond. Concentrating on our pond outlet the pH has come in at 7.0 the guideline is 7.0 to 8.5. The minerals tested for are Boron, Calcium, Copper, Iron, Magnesium, Manganese, Potassium, Sodium, Zinc, Chloride, Sulphate and of course Nitrate, the one that gets all the authorities excited. All minerals except Iron and Manganese were well below acceptable guidelines including the nitrate. As this is a relatively free draining soil a lot of the water filters down through the earth and collects iron and manganese on the way. Both these elements can be filtered out fairly easily if the water is required for drinking. Now the nitrate tested at 0.52 and the guideline is to be below 11.3. Our pond nitrate level was miles below what the World Health Organisation accepts. The comment from the testing people was that nitrate was detected, but at such a low level to be of no concern. Iron was above desirable level, but not toxic, however manganese not so desirable. A further comment was that the water was described as ‘very soft’. This contrasts with our test from the Ohinemuri River where the water was described as ‘hard’. A simple test means ‘soap’ lathers easily in soft water, but not so in hard. In 2020 in the severe drought conditions fish eels and ducks were all dying in the water on the Hauraki Plains, in sharp contrast to our situation, where the birds and eels were unscathed. Obviously changes in the farming system practised can change the water quality leaving the property.
The practice of regular spraying to kill vegetation on road edges, along drains, and the sides of roads which has been going on for years, destroys water quality that ends up in our rivers and then eventually feeds back to farms. Wherever you spray, it ends up in the water and there’s a lot of water on the Coromandel.
Malcolm Campbell has been farming for seventy years. He is a writer and scientist, author of six books, a careful methodical recorder of data, a pilot and a friend to his community. He has lived through all manner of changes in local government structure and management. He writes to raise the level of awareness of policies and consequent operations that discourage and even destroy good land farming practises and production.
Caption: Malcolm Campbell.