A paper published in the Journal of Environmental Quality reveals that a significant proportion of water quality degradation occurs in small streams which currently fall outside the regulations requiring waterways in agricultural land to be fenced.
The paper was contributed by Dr Rich McDowell who is Chief Scientist on the Our Land and Water National Science Challenge.
The research which the paper reports on was developed to test "if potential regulation in New Zealand requiring livestock to be fenced off from large (high)-order streams would substantially decrease catchment contaminant loads."
The research team used available data from 728 water quality testing sites covering the period from 1998 to 2009 to calculate loads and yields of nitrogen, phosphorus, suspended sediment and e-Coli.
The research found that 77% (on average) of the national contamination load came from small streams - those less than a metre wide and 300 centimetres deep.
The authors concluded that if NZ wants "to substantially reduce contaminant losses, other mitigation should be investigated in small streams, particularly where fencing of larger streams has low efficacy."