Water pollution in New Zealand is an increasing concern for environmentalists and regulatory bodies. An increase in dairy farming in New Zealand is linked to an increase in water pollution, and siltation due to land clearance has affected lakes, rivers, caves and bays. There are more than 800 water quality monitoring sites around New Zealand that are regularly sampled.[1]
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Agriculture is the dominant use of land in New Zealand and has had the most widespread impact on water quality. In recent years water pollution has increased since stocking rates are becoming higher and there is an increasing use of fertilizers. Horticulture, arable farming and plantation forestry have a lesser impact than dairy farming.[1]
In 2001 Fish and Game New Zealand started the high profile "dirty dairying" campaign to highlight the effect of pollution from dairy farming intensification on the ecological health of freshwater environments. As a reaction to this campaign Fonterra, the largest dairy company in New Zealand, along with a number of government agencies instigated the Dairying and Clean Streams Accord to address water pollution due to dairy farming. The aim of the Accord is to limit the access of stock to waterways. Fonterra exports the majority of its produce and encouraging farmers to limit environmental impacts is a method of getting environmentally aware consumers to purchase their products. In a report released in October 2008 Fish and Game and Forest and Bird were highly critical of the Accord.
Urban runoff is polluted with detergents, waste oil, litter and fecal matter. Some stormwater drains have a fish logo pained on the curb to highlight stormwater pollution.
High numbers of visitors to parks and other areas where there are no toilets is increasing the chance of pollution from human waste. In alpine areas, where anaerobic digestion of fecal matter is slow, the Department of Conservation have sewerage holding tanks on the toilets at backcountry huts. The sewerage is flown out by helicopter for treatment elsewhere. Freedom camping, a popular activity in some areas, is suspected of causing water pollution due to the incorrect disposal of human waste.Which comes from sewage overflow.
The most significant source of water pollution in urban areas is due to sewerage. Broken sewers and faulty connections allow sewerage to enter stormwater systems.[1] Also, during flooding sewerage pumping stations are inundated with the floodwaters and sewerage is released.
Water run-off from roads contains pollutants such as zinc, copper, lead and hydrocarbons from vehicle wear, vehicle emissions and from the road surface itself.[1] Urban areas have large amounts of paved surface therefore there is a higher likelihood that water contaminated with organic matter will not be filtered through soils.
Sediment run-off from exposed soils in new subdivisions does occur and if it occurs due to breaches of the resource consent prosecution may result. To limit sediment run-off during earthworks straw bales and stormwater settling ponds are used.
Regional councils have the responsibility to address water use and misuse issues as set out in the Resource Management Act, a significant Act of Parliament that regulates natural and physical resources such as land, air and water. Differing land use and climate means that water pollution varies across the regions.
| Region | Allocation and abstraction | Water quantity |
Surface water quality | Groundwater quality |
Future demand |
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| Surface water | Ground water | Surface water | Ground water | Micro biological | Inorganic | Micro biological | Inorganic | Proposed irrigation schemes | |
| Canterbury | Increasing | Increasing | Uncertain | Uncertain | Uncertain | Uncertain | Uncertain | Decreasing | Increasing |
| Hawke's Bay | Increasing | Increasing | Steady | Decreasing | Uncertain | Uncertain | Uncertain | Decreasing | Increasing |
| Waikato | Increasing | Increasing | Uncertain | Uncertain | Decreasing | Decreasing | Uncertain | Decreasing | Steady |
| Southland | Steady | Increasing | Steady | Steady | Uncertain | Uncertain | Decreasing | Uncertain | Uncertain |
The above table is an aggregate of water trends in the regions and it shows no trends in water quality improvement or the related issue of water abstraction. However, there are observed improvements in water quality for some water bodies in some cases.
The Tarawera River, nicknamed "the black drain", has had a history of water pollution, predominantly due to industrial activity.
Historically much of Canterbury has been dry land and arable farming but there has been a huge increase in dairy farming in the region. Dairy farming in Canterbury requires large amounts of irrigation since the average rainfall is too low to support dairy cow pastures.
The Central Plains Water scheme, currently going through the hearing process in order to obtain a resource consent, is a controversial plan due in part to the anticipated impact on water quality. When completed it will be used to irrigate 60,000 ha of the Canterbury Plains with water taken from the Rakaia and Waimakariri Rivers.
The Heathcote River has been subjected to a number of recent pollution incidents.
In Southland effluent from dairy sheds used for more than 50 cows needs a resource consent. Environment Southland recommends effluent is spread at a rate of eight hectares per 100 cows and should not applied to wet soils.[3]
The Waikato has had a long history of dairy farming and has some of the most productive soils in the country. Water quality, especially as shown by the indicators of conductivity and pH, in the Waikato Region is deteriorating.[4]
The Waikato River has a high level of pollution due to various point and non-point sources.
The West Coast receives a high rainfall so any potential pollution will be diluted to some degree.
Until recently untreated sewerage was being discharged into the Grey River but government funding was made available to build a sewerage treatment plant.