Myth: Water pollution comes mainly from urban sources.

Reality: Polluted urban water makes up a small amount of the pollution in waterways as urban areas only cover a small length of the total streams and rivers in New Zealand.

The response from farming groups to water quality issues is that a lot of pollution is caused by urban areas. In reality, less than five per cent of the output comes from the public in urban areas [1], and that is all treated for bugs. Urban pollution is not the biggest problem by far.

Although urban streams are generally worse in quality than streams in other land uses, they only cover a small length of the rivers in New Zealand and account for about four per cent of the stream and river sites tested in New Zealand.  Additionally, there are often agricultural areas upstream of urban centres, so there will be various sources of pollutants in these streams.

Dairy cow poo

Cattle produce a lot of waste that is deposited on the land without treatment. Faecal bacteria pollution from dairy cows alone represents concentrations equivalent to over 90 million people’s raw sewage onto the land [2]. This leaks through the soil to the aquifers, contaminating both well sources and surface water with sewage bugs and nutrients. Sewerage pollution from humans in New Zealand is minuscule compared to this.

Dairy is worse than other land uses because it contributes to a disproportionate amount of pollution in catchments [3] and dairy cows excrete more waste than other stock types [1].

References:

[1] Fleming, R. and Ford, M. (2001) Human versus animals – Comparison of waste properties. University of Guelph Retrieved from here.

[2] Environment Waikato (2008). The condition of rural water and soil in the Waikato region: Risks and opportunities. Read the report here.

[3] Davies-Colley, R. and Nagels, J.W. (2002) Effects of dairying on water quality of lowland stream in Westland and Waikato. Proceedings of the New Zealand Grassland Association, 64, 107-144;
Ministry for the Environment (2009). Water quality in selected dairy farming catchments: A baseline to support future water-quality trend assessments. Wellington, New Zealand;
Townsend, C.R.; Arbuckle, C.J.; Crowl, T.A. and Scarsbrook, M.R. (1997). The relationship between land use and physicochemistry, food resources and macroinvertebrate communities in tributaries of the Taieri River, New Zealand: A hierarchically scaled approach. Freshwater Biology, 37: 177-191.

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