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Relative effects of river flow, water temperature and abstraction on trout in the Torepatutahi stream

TR 2001/09

Relative effects of river flow, water temperature and abstraction on trout in the Torepatutahi stream

Report: TR 2001/09
Author: D Speir & I Kusabs

Abstract

Increasing demand for water for out of stream uses such as irrigation and community supply have the potential to adversely effect the value of the Torepatutahi stream as a significant habitat for resident trout populations and as cold water refuge for trout from the Waikato River. Changes in water level resulting from increased out of stream water use also has the potential to reduce the area and quality of marginal wetlands in the mid reaches of the stream.

In order to investigate these potential effects Waikato Regional Council conducted detailed investigations on the fishery, flow regimes and temperature of the Torepatutahi Stream over a four month period.

Relative Effects of River Flow, Water Temperature and Abstraction on Trout in the Torepatutahi Stream
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Table of contents

Executive Summary
1 Introduction
 1.1 Background
2 Objectives
3 Methods
 3.1 Drift diving
 3.1.1 Site selection
 3.2  Water Temperature Monitoring
 3.3  Waikato River Level Fluctuation
 3.4  Water Abstraction and Stream Flow Monitoring
4 Habitat Descriptions
 4.1.1  Upper Dive Section
 4.1.2  Lower Dive Section
 4.1.3  Confluence Dive Section
5 Results
 5.1  Dive conditions
 5.2  Species composition and abundance
 5.2.1  Species composition
 5.2.2  Trout abundance
 5.3  Water Abstraction and Stream Flow Monitoring
 5.4  Water Temperature
 5.5  River Level Fluctuations
6 Discussion
 6.1  Trout abundance
 6.1.1  Cold water refuge
 6.1.2  The Torepatutahi as habitat for trout
 6.1.3  Trout spawning and juvenile rearing habitat
 6.2  Water Abstraction and River level fluctuations
 6.2.1 Mixing Zone and Cold Water Plume
 6.2.2  Water Level Effects
7 Conclusions And Recommendations
8 References
Appendix 1: River And Stream Temperatures
Appendix 2: Waikato River Levels