Dairy intensification and fresh water quality


In 2014 for a Masters-level course at Massey University, I wrote an assignment examining dairy intensification with relation to water quality issues. The report is based on dairying in the Canterbury region using the Natural Resources Regional Plan (current at the time of the report; since superceded by the Land and Water Regional Plan). Below is an excerpt of the report, where several indicators pertaining to fresh water quality, were identified (based on N.R.R.P. Table WQL 5):

  1. Ecological Health – Ecological health measures a water way health based on the impacts of human activities and natural changes to its system (Glennie J., pers comm.). It uses such indicators as the Quantitative Macroinvertebrate Community Index (Q.M.C.I.), which scales the sensitivity of taxa to pollutants.
  2. Nutrient Indicators – Macrophytes and periphyton are key microbiological organisms which form mats of weed in rivers and can impede water flow, changing the characteristics of the aquatic life, the water way as a fishery and its aesthetic values. These require high nutrient input, which is readily available on dairy farms through cattle faeces and urine being discharged into unprotected water ways, but also from fertilizer application on land (Environment Canterbury, 2011, pp 32-34).
  3. Siltation – Siltation is a major problem in spring fed water ways, which are numerous in Canterbury. Their margins get degraded by uncontrolled cattle herds, trampling the banks, which are normally soft sediment, easily broken up by hooves and dissolved in flowing water (Environment Canterbury, 2011 pp 32-34).
  4. Micrbiological organisms – These are faecal organisms from dairy animals, that have found their way into water ways (Glennie J., pers comm.). Concentrations of these organisms affect the quality of water involuntarily ingested during recreation, and also the health of livestock that may come in contact with the water.
  5. Toxic algal growth – This particularly relates to cyanobacteria, which has been linked to dog deaths. This is most prevalent during summer when temperatures are warmer and natural flows are lower, allowing sunlight to warm the water and encourage algal growth (Environment Canterbury, 2011, pp 32-34). The growth can be exacerbated by water having phosphate and nitrogen as these are necessary for photosynthesis
  6. Fisheries – Fishing is a popular recreational past time in Canterbury where numerous fresh fishing opportunities afford themselves (Environment Canterbury, 2011, pp 32-34). Fisheries can suffer from degraded water ways if the insect life that they feed on, is depleted. If siltation is occurring it can damage spawning beds and make difficult for future generations of fish

It is only a matter of time when dairy intensification begins in places such as the Heretaunga Plains of the Hawkes Bay or the Canterbury Plains before the quality of the drinking water starts to be affected. The nutrients being washed off farms and into waterways filters into the gravels. Recharge zones such as those around west of Christchurch are particularly prone due to the high intensity of dairy herds. Last year 14 separate incidents in which the aforementioned microbiological organisms got into Christchurch drinking water were idenitified. The acceptable limit of such organisms per unit of drinking water is zero (0).

 

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