Water quality of a lowland stream in a New Zealand dairy farming catchment

A small stream in a predominantly dairying catchment in the Waikato region of New Zealand was monitored for 2 years at three sites. Total nitrogen (TN) concentrations were up to 7.09 g m(-3) in winter, with the bulk comprising nitrate nitrogen (NO3--N). During summer NO3--N was near zero and TN mostly comprised organic nitrogen. Maximum concentrations of total phosphorus (TP) and dissolved reactive phosphorus (DRP) were 1.64 and 0.555 g m-3, respectively, and peaks coincided with spring and autumn applications of phosphorus fertiliser. Ammoniacal nitrogen concentrations exceeded 1 g m(-3) on several occasions and mean concentrations at the three sites were 0.165-0.272 g m(-3). Faecal coliform and enterococci bacteria concentrations were 64-26000 and 7-23000 cfu per 100 ml, respectively. Specific yields of TN and NO3--N (35.3 and 30.7 kg ha yr(-1), respectively) were much greater than any previously reported for New Zealand pasture catchments, whereas TP and DRP yields (1.16 and 0.54 kg ha yr(-1), respectively) were more in accord with other studies. Greater use of land treatment of liquid wastes will reduce stream inputs of faecal organisms, NH4-N and P.