Land‐use impacts and water quality targets in the intensive dairying catchment of the Toenepi Stream, New Zealand

Abstract

Water quality monitoring in Toenepi Stream, New Zealand, started in 1995 in a study of dairy farming influences on lowland stream quality and has continued since then with brief interruptions. Surveys have provided information about changes in farm and soil management practices as they relate to environmental sustainability. Although average water quality in Toenepi Stream has changed little during 1995-2004, there have been some notable improvements. Water clarity measured by black disc has improved from 0.6m to 1.5m, and median ammonia-N and nitrate-N concentrations have declined by 70% and 57%, respectively. The frequency and magnitude of extreme concentrations have declined-most notably for nitrogen (N) forms, which also had decreased mean values. Specific yields for suspended solids (SS) and phosphorus (P) forms in 2002-04 were 47-67% of 1995-97 values, mainly because of lower water yields. Reduced specific yields for N forms in 2002-04 (34-37% of 1995-97 yields) were also attributable to lower mean concentrations in stream water. Faecal bacteria concentrations have not abated and are on average 2-3 times recommended guideline values for contact recreation. Fewer dairy farms and an increased proportion irrigating dairyshed effluent to land, rather than discharging it to the stream via twopond systems, were likely causes of improvement in water quality. Water quality targets were developed for Toenepi Stream to achieve contact recreation criteria for the Piako River (downstream) and for intrinsic habitat values for Toenepi Stream. A range of mitigation measures has been formulated to meet these targets, but substantial uptake of sustainable farming practices is needed to improve water quality in Toenepi Stream.

Effectiveness of a Natural Headwater Wetland for Reducing Agricultural Nitrogen Loads

“…The Toenepi catchment is intensively farmed and 75% of the catchment area is under dairy production with a stocking rate of 3 cows ha −1 [27]. The mean annual rainfall of the area is 1377 mm.…”

Managing pollutant inputs from pastoral dairy farming to maintain water quality of a lake in a high-rainfall catchment

“…Dairy farming comprises 32.8 km 2 (8%) of the Lake Brunner catchment (Rutherford et al 2008). The catchment is one of five wholly or predominantly dairy farming catchments in New Zealand where changes in water quality that derive from adoption of best management practices, such as riparian stock exclusion and vegetation are being examined (Wilcock et al 2007;Monaghan et al 2008).…”

“…Study catchments (6-41 km 2 ) were chosen to be representative of the farming methods and challenges for environmental sustainability within each region, with stream median flows ranging from ,70 to 500 L s À1 (Wilcock et al 2007).…”

“…Stream water was analysed for conductivity (AE0.01 mS cm À1 ), in situ temperature (AE0.058C) and dissolved oxygen (DO) (AE2% saturation), turbidity (AE0.01 NTU), dissolved organic carbon (DOC) (AE0.02 g m À3 ), suspended solids (SS) (AE0.5 g m À3 ), Escherichia coli (AE1 MPN (100 mL) À1 ), nitrate plus nitrite nitrogen (N) (NO X -N) (AE0.001 g m À3 ), ammoniacal N (NH 4 -N) (AE0.001 g m À3 ), TN (AE0.01 g m À3 ), filterable reactive phosphorus (P) (FRP) (AE0.001 g m À3 ) and TP (AE0.001 g m À3 ). Total organic N (TON) (AE0.002 g m À3 ) was calculated from TN minus DIN, where DIN ¼ NO X -N þ NH 4 -N. Standard protocols for sample collection, stabilisation and analysis were adopted for all water quality variables (APHA 1998;Wilcock et al 2006). E. coli concentrations were measured by the Colilert most probable number (MPN) method (IDEXX Laboratories, United States).…”

“…A dairying catchment monitoring study initiated in the Inchbonnie Valley in 2004 sought to understand and mitigate impacts of dairy farming on Lake Brunner. The study was part of a national, catchments-based monitoring study (Best Practice Dairying Catchments for Sustainable Growth) that examined the linkages between dairy farming and receiving water quality and derived appropriate tools for mitigating adverse effects (Wilcock et al 2007;Monaghan et al 2008). Two catchments in the study are located in established dairying areas of the North Island, while the Inchbonnie catchment is one of three that are in the South Island of New Zealand (Wilcock et al 2007;Monaghan et al 2008).…”