No.25 2007

The science behind clean waterways
NIWA’s Kerry Costley working at an Environment Waikato Clean Stream site. (Photo: Rob Davies-Colley, NIWA)
NIWA scientists are leading the way in developing sciencebased solutions for the restoration of New Zealand’s degraded streams, rivers, and lakes.

Fish models help conservation
Predicted shortfinned eel distribution, North Island.
New Zealand’s native fish species are a key component of our freshwater biodiversity. New statistical models which depict the distribution of 30 native species are playing a valuable role in their conservation management and will be valuable in setting restoration targets.
The models have been developed by NIWA and Department of Conservation scientists using fish distribution data from the New Zealand Freshwater Fish database, along with environmental data.

Water resources outlook (December 2007 - February 2008)
Northern North Island: Above normal soil moisture levels and river flows are likely.
Southeastern North Island: Normal or below normal soil moisture levels and river flows are likely.
Southwestern North Island & Northern South Island: Normal soil moisture levels and river flows are likely.
Southwestern & eastern South Island: Below normal soil moisture levels and river flows are likely.

Solving the P problem
 
Dr Steph Parkyn lowering a koura cage used to evaluate the effects of modified zeolite addition to Lake Okaro on koura health. (Photo: Chris Hickey, NIWA)
Restoration of lakewater quality is frequently constrained by ongoing ‘internal loading’ of phosphorus (P), which is released from lake sediment into the water under certain conditions.
One possible remedy is to add compounds to the lake which deactivate the phosphorus.

Restoring streams on farmland – a win-win story
Reduction in soil erosion (measured by sediment reaching water courses) following the implementation of integrated catchment management (ICM) practices in 2000-01.
A comprehensive programme of sustainable land management, on a hill farm catchment in the Waikato, has proved that sound environmental practices can improve both stream water quality and farm economic performance – a win-win for farmers and the environment.
The land-use changes made on the Mangaotama catchment included planting radiata pine in the steepest parts of the ca

Water resources review (September - November)
River flows
September - November river flows
River flows over the last 3 months were below normal for South Island east coast, Wellington, and North Island East Cape. Northland, Hawke’s Bay, and southwest South Island had above normal flows. Flows elsewhere were normal.
[Water resources information provided by NIWA field teams, regional and district councils, and hydropower companies.]