No.16 2006

Management of Auckland's water supply lakes reviewed
Lake Nihotupu, one of ten water supply reservoirs for Auckland.
Recently, NIWA reviewed aspects of raw water management for the ten lakes supplying Auckland’s water.
Watercare Services Limited, which operates the lakes, has extensive and well documented operational procedures for water collection, treatment, and water quality monitoring. The water consistently meets the required drinking water standards, but there have been a number of complaints in recent years about its taste or smell.

Lake edge plants could help small lakes
Installing temperature measuring equipment amongst jointed twig rushes at Lake Okareka.
Lake Okareka, in the Rotorua district, still has clear water, but is showing early signs of deterioration. A NIWA study is investigating the importance of vegetation growing on the lake edge in protecting the water quality – with potential application to other lakes.
Bands of tall, emergent plants such as raupo, kuta, and jointed twig rush grow in parts of Lake Okareka out to about 3 m depth.

Lake Okaro farming family, the Birchalls, gifted the use of 2 hectares of land for the project. "It was quite a big decision for us but we wanted to do it for future generations," says Shane Birchall (pictured). Another 0.3 hectares of reserve land was provided by the Rotorua District Council.
The wetland under construction (photo : Opus International Consultants).
Lake Okaro in the Rotorua district is popular with water skiers, but experiences persistent blue-green algal blooms most summers.

Water resources outlook (April - June)
The following soil moisture levels & river flows are likely:
Northern North Island: normal or above normal
Southwest North Island: below normal
Southeast North Island: normal
North & southwest South Island: normal or below normal
Eastern South Island: below normal

Water resources review (January - March)
River flows
Normal river flows occurred in much of the North Island and coastal Southland. Below normal flows occurred in Taranaki, Kapiti Coast, Nelson, and the central South Island. Flows were particularly low in the catchments originating from the main divide of the Southern Alps.
[Water resources information provided by NIWA field teams, regional and district councils, and hydropower companies.]