Water quality in low‐elevation streams and rivers of New Zealand: Recent state and trends in contrasting land‐cover classes

Abstract

River water quality in New Zealand is at great risk of impairment in low elevation catchments because of pervasive land-use changes, yet there has been no nationwide assessment of the state of these rivers. Data from the surface-water monitoring programmes of 15 regional councils and unitary authorities, and the National River Water Quality Network were used to assess the recent state (1998-2002) and trends (1996-2002) in water quality in low-elevation rivers across New Zealand. Assessments were made at the national level, and within four land-cover classes (native forest, plantation forest, pastoral, and urban). Finer-scaled assessments were made by subdividing the large number of pastoral sites into six climate classes, and seven stream orders. At the national level, median concentrations of the faecal indicator bacterium Escherichia coli, and dissolved inorganic nitrogen and dissolved reactive phosphorus exceeded guidelines recommended for the protection of aquatic M03047; Online publication date

Trends in water quality of five dairy farming streams in response to adoption of best practice and benefits of long-term monitoring at the catchment scale

“…Water quality status, trends and causes Degraded water quality is a feature of streams in intensively farmed pastoral catchments in New Zealand, such as those monitored in this study (Larned et al 2004;Quinn et al 2009). …”

“…A consequence of increased stocking rates has been a concomitant increase in nutrient leakages from farm systems and increased inputs of sediment and faecal microbes to aquatic ecosystems (Ledgard et al 1999;Quinn et al 2009;Wilcock et al 1999Wilcock et al , 2007. Land use changes from sheep and beef cattle grazing to more intensive dairy farming have caused marked deterioration in the water quality of New Zealand's low-elevation streams and rivers (Larned et al 2004;Howard-Williams et al 2011). Of the pastoral land use category, which makes up 42% of New Zealand's land cover, dairy farming has the highest diffuse pollution footprint with 36.7% of the total N load entering the sea originating from the 6.8% of the land area occupied by dairy farming (HowardWilliams et al 2011).…”

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

“…Faecal pollution, as indicated by E. coli data, ranged from negligible (5 MPN (100 mL) À1 ) to very high (41060 MPN (100 mL) À1 ), but the median concentration (405 MPN (100 mL) À1 ) was similar to that of other dairy catchment streams (Wilcock et al 2007). FRP comprised 62% of TP and was similar to that of the other monitored dairy streams (Table 2), compared with an average of ,36% for pastoral streams in general (Larned et al 2004). Pigeon Creek TN concentrations were generally lower than in the other monitored dairy catchment streams in New Zealand (Table 2).…”

“…Pigeon and Homestead Creeks are low-gradient streams with water quality that is similar to other streams in agriculturally developed catchments in New Zealand (Larned et al 2004;Wilcock et al 2007). The very high flood frequency distinguishes the streams by giving them some resilience to pollutant accumulation.…”

Special issue on restoration of aquatic ecosystems

“…5% plantation forest and 1% urban, Ministry for the Environment 2007), 40% of all lake catchments (Ministry for the Environment 2007), and 55% of all estuaries (estuarine classification database, hume et al (2007)). Waterbodies with predominantly pastoral catchments are typically degraded to varying degrees relative to those with natural vegetation cover (Larned et al 2004;Parkyn & Wilcock 2004;Sorrell et al 2006; Ministry for the Environment 2007) and diffuse source pressures from agricultural land use are believed to be the most significant pressure on fresh waters (Ministry for the Environment 2007). Therefore, this relative abundance of reference ecosystems in reserves (albeit with lowland systems under-represented) and the predominance of agriculture-related stressors provides particular opportunities for New Zealand to contribute to the international development of aquatic restoration science.…”