Interesting lead article on freshwater in the relaunched NIWA magazine, Water and Atmosphere.
Trend is worsening: NIWA states that water quality is degrading in our major rivers and that the ‘upward trend in temperature, nitrogen and phosphorus has strengthened in recent years’.
Source of the pollution: ‘pastoral farming… is undoubtedly the main source of diffuse pollution… Streams in dairy land are among the most polluted.’
And why the decline in water quality: ‘There is no doubt that our declining river water quality over the last 20 years is associated with intensification of pastoral farming and the conversion of drystock farmland to dairy farming, particularly in Waikato, Southland and Canterbury.’
Why is dairy such a problem: ‘dairy farming is a leaky process… the average nitrogen lost from the soil on dairy farms was 39 kg per hectare per year.’
Hence, there are limits to mitigation: ‘best management practices can only do so much’.
So should we recklessly expand dairying?: NIWA are ‘concerned about the expansion of dairying into high rainfall or heavily irrigated areas where there is a greater risk of contaminants getting washed into waters.”
And what is the government doing – well NIWA can’t say this but the Govt is planning to rapidly expand dairying in areas like Canterbury where it will result in even more dramatic pollution.
The whole article is worth a read.