Fishing News >March 2008

Otago River Flows Workshop

Setting minimum flows for rivers and streams is a complex issue, particularly with an increasing demand for water for irrigation and hydro generation.  These decisions are important for anglers, but they are made by regional councils through their water plans (if they have one in place that is).

One of the useful things to come out of Government’s ‘Sustainable Water Programme of Action’ is a planned ‘National Environmental Standard’ on the setting of minimum river flows.  This high level policy, developed under the RMA, will guide regional councils in the development of their new water plans on how to set minimum flows as well as putting default provisions in place where regional councils don’t have a plan.

The national standard will be released for public submissions in the next month or so but there is a debate amongst scientists and freshwater fisheries managers about what tools to use to determine minimum flows.  Otago’s Flow workshop came about because of concerns that Department of Conservation and Fish and Game advice on flow setting methodologies could diverge.  Such a difference of opinion is only likely to complicate policy development and benefit out of stream water users to the detriment of trout and native fish.  The primary aim of the workshop was to help develop a common Fish &Game /DOC position on flow setting.

At the present time river flow setting exercises in New Zealand rely heavily on a methodology involving computer simulation of habitats based on limited physical habitat measurements (particularly depth and velocity) from a specific river reach or reaches.  Often the method does not consider natural flow characteristics such as flow duration, frequency, timing, magnitude and rate of change of flows when setting limits.  By comparison the holistic approaches supported by DOC incorporates natural flow characteristics. Flows that mimic natural flow characteristics are seen as important in maintaining functioning river ecosystems for both native and sports fish, and so for recreation.

DoC and Fish and Game representatives from around the country (but mostly from the South Island) debated the issue and decided on a strong preference for a holistic approach to flow setting methods, and also identified a need to review the effectiveness of habitat simulation methods as applied in New Zealand

The group felt that monitoring of fish populations and other biota should become part of regional council state of the environment reporting in order to establish baselines against which the effects of flow regime changes can be measured.  And they decided flow setting exercises needed to include consideration of flows for recreational use and aesthetics, amongst other things.

The workshop recommendations have gone out to the 12 regional Fish and Game Councils and the New Zealand Council for further consideration but a consensus is beginning to emerge which should result in a common position on flow setting by the time the draft national standard is advertised.

Niall Watson

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