The Waikato River is New Zealand’s longest river, running 425 km from Mt Ruapehu to the Tasman Sea at Port Waikato. Since 2002, the Waikato River has also been part of Auckland’s water supply network, providing an average of 37,000 m3 of water to the region each day, meeting between eight per cent and 15 per cent of the area's annual needs, depending on weather conditions and dam levels. At times during the 2013 drought, the Waikato was supplying almost 30 per cent of Auckland’s water (less than one per cent of the river’s volume).
Waikato River water is treated at the Waikato Water Treatment Plant, which is located in Tuakau, less than 40 km from the river mouth. Watercare currently has resource consent to take up to 150,000 m3 per day from the river.
In order to meet the expected increase in demand for water generated by the Auckland region’s growing population, Watercare has applied for consent to take an additional 200,000 m3 of water per day from the Waikato River.
Other options considered include new dams in the Riverhead Forest and at Lower Mangatawhiri (neither of which is sufficient, either alone or in combination, to meet the predicted demand, and both of which would entail significant environmental impacts) and a desalination plant (which was ruled out on cost and environmental considerations).
The effects of the proposed abstraction on the river as it flows past Watercare’s treatment plant will be: A water level change of between 15 mm and 22 mm, compared with a typical water depth of approximately 6 m and a daily tidal variation of approximately 0.5 m; A change in mean velocity of between 0.004 m/s and 0.002 m/s compared with a mean velocity in these conditions of approximately 0.5 m/s.
Independent experts have assessed that the predicted changes will have no significant effect on water temperature, and changes in dissolved oxygen levels will be largely undetectable to wildlife or river users.
Consultation has been undertaken with bordering local authorities, Waikato-Tainui, mana whenua, key users of the Waikato River such as power companies and agricultural and horticultural users, and other potentially affected and/or interested parties including environmental groups. Watercare is committed to maintaining open dialogue with key stakeholders throughout the consenting process.
Watercare has set a water savings target of reducing per capita consumption to 15 per cent below 2004 levels by 2025. Records to date show that Watercare is on target to achieve these savings. Auckland already outperforms other cities in New Zealand and overseas in respect of its water conservation.