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Water is relatively abundant in New Zealand due to the temperate climate and maritime weather patterns. In recent years, water pollution and draw-down of aquifers have become important environmental issues.
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Waters in New Zealand
In New Zealand, there are more than 425,000 km of rivers and streams, about 4,000 lakes and over 200 underground aquifers. Annual water flow is 145 million litres per person. The reliable supply of good water is an important economic advantage for New Zealand, but its quality and availability is declining.
Lakes
There are 3,820 lakes in New Zealand with a surface area larger than one hectare and are of varying types and origins. Many of the lakes in the central North Island area are volcanic crater lakes, while the majority of the lakes near the Southern Alps were carved by glaciers. Hydroelectric reservoirs are common in South Canterbury, Central Otago and along the Waikato River.
Rivers
Over 180,000 kilometres of rivers has been mapped in New Zealand, the longest being the Waikato River with a length of 425 kilometres and the largest river by volume is the Clutha River with a mean discharge of 533 cubic metres per second.
Waterfalls
New Zealand has many notable waterfalls, some of which are regularly visited by tourists. Huka Falls on the Waikato River is one such waterfall. Sutherland Falls is usually regarded as the highest waterfall in New Zealand at 580 metres high but Browne Falls cascades 619 m or 836 m depending on what is considered to be the source. The Maruia Falls on the Maruia River are a relatively new waterfall formed as a result of the 1929 Murchison earthquake.
Hydrology of New Zealand
The average annual precipitation for New Zealand as a whole is 2.1 m. In mountain portions of the West Coast, it exceeds 10 m per year. The distribution of precipitation across the country is determined by its location with the mid-southern latitudes and its topography. Seasonal differences in precipitation are substantial, regularly leading to summer water deficits in many parts of the country, though the season of greatest and least precipitation differ from region to region. The amount of precipitation also varies interannually in response to both ENSO and IPO cycles.
Water resource use
Water resources are used for a number of purposes, including hydroelectricity generation, irrigation, and municipal water supply. Approximately 2% of New Zealand's freshwater resource is allocated for consumptive use.
Legislation
The Resource Management Act 1991 governs the use of water (and other natural resources). A resource consent is required for taking, damming, discharging and diverting water. The lack of a National Policy Statement on freshwater is often cited as a reason for ineffective management of water resources
Hydrological and water resource changes
In modern times, the quantity, quality and timing of water within New Zealand has been changing. Principal causes have been abstraction, impoundment, land use and land cover change, and agricultural and industrial runoff.
Pollution
Water pollution in New Zealand is becoming an increasing concern for environmentalists and for regulatory bodies.
An increase in dairy farming 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.
Organisations
Various organisations in New Zealand are involved with water and its use. Regional Councils have the statutory responsibility for water.