Preliminary Nutrient Guidelines for Victorian Inland Streams
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PRELIMINARY NUTRIENT GUIDELINES FOR VICTORIAN INLAND STREAMS Publication 478 June 1995 PRELIMINARY NUTRIENT GUIDELINES FOR VICTORIAN INLAND STREAMS David Tiller and Peter Newall Catchment and Marine Studies Environment Protection Authority Government of Victoria June 1995 PRELIMINARY NUTRIENT GUIDELINES FOR VICTORIAN INLAND STREAMS Catchment and Marine Studies Environment Protection Authority Olderfleet Buildings 477 Collins Street Melbourne Victoria 3000 Australia June 1995 ISBN 0 7306 2839 6 FOREWORD The community is becoming increasingly aware and concerned with the problems of nutrient enrichment of water bodies, and the influence of high nutrient concentrations in supporting undesirable algal blooms. In response to this concern the Victorian Government has developed a Nutrient Management Strategy. A major part of the strategy involves the implementation of Catchment Nutrient Management Plans (CNMPs), which will focus on the rehabilitation of water catchments and streams that have been degraded through poor land management, excessive land clearance, and poor stream management. An important step in the development of CNMPs is the establishment of nutrient targets. This report outlines preliminary guidelines for phosphorus and nitrogen concentrations in Victorian inland streams to assist in the development of CNMPs and to aid in the protection of the aquatic environment. Preliminary guidelines have been determined for seven river regions across the State with similar environmental attributes and stream systems. Within each river region, pertinent available biological and nutrient data were collated allowing an assessment of background, threshold and "major impact" nutrient concentrations. During the preparation of these guidelines, deficiencies in knowledge on stream ecosystem responses to nutrients for several regions in Victoria were highlighted. There is clearly a need for additional research to further our knowledge. As such, these guidelines must be viewed as preliminary. It is expected that their publication will stimulate input and discussion from interested parties. Following this feedback, and any subsequent revision, the guidelines will provide, where appropriate, input into CNMPs and State environment protection policies. BRIAN ROBINSON CHAIRMAN iii ACKNOWLEDGEMENTS The authors thank the following people for their reading, comments and re-reading of the drafts of this report: from EPA's Catchment and Marine Studies Unit, all Freshwater Studies staff, Chris Bell and Lisa Dixon; Rohan Ash, Greg Creek, Phillip Johnstone, Carsten Osmers and Greg Sheehan (EPA); and Peter Vollebergh from the Water Resources Management Branch of the Department of Conservation and Natural Resources. v CONTENTS FOREWORD.............................................................................................................................. iii ACKNOWLEDGEMENTS........................................................................................................ v 1. INTRODUCTION ....................................................................................................... 1 1.1 Background.......................................................................................... 1 1.2 Scope ................................................................................................... 1 1.3 Aims..................................................................................................... 2 2. APPROACH................................................................................................................ 3 2.1 Introduction.......................................................................................... 3 2.2 Information Sources ............................................................................. 3 2.3 The River Regions................................................................................ 3 2.3.1 Highlands River Region ......................................................... 4 2.3.2 Murray Foothills River Region............................................... 4 2.3.3 Murray Plains River Region ................................................... 4 2.3.4 Southern and Isolated Foothills River Region......................... 4 2.3.5 Northwest Plains River Region............................................... 5 2.3.6 Southwest River Region......................................................... 5 2.3.7 Southern Lowlands and Urban River Region.......................... 5 3. HOW TO USE THE GUIDELINES............................................................................. 9 3.1 Guideline Concentrations ..................................................................... 9 3.2 Current Nutrient Concentrations Versus the Guidelines ........................ 9 3.3 Flows ................................................................................................... 9 3.4 Geographical Precision of the Regions and Guidelines ......................... 10 4. THE NUTRIENT GUIDELINES................................................................................. 11 4.1 Highlands River Region ....................................................................... 11 4.2 Murray Foothills River Region ............................................................. 12 4.3 Murray Plains River Region ................................................................. 13 4.4 Southern and Isolated Foothills River Region ....................................... 14 4.5 Northwest Plains River Region............................................................. 15 4.6 Southwest River Region ....................................................................... 16 4.7 Southern Lowland and Urban River Region.......................................... 17 5. CONCLUSIONS.......................................................................................................... 20 6. REFERENCES CITED................................................................................................ 23 Nutrient Guidelines 1. INTRODUCTION 1.1 Background Nutrient concentrations in most surface water bodies across Victoria have increased through human activities that have created a variety of diffuse and point source inputs (Department of Water Resources 1989). Elevated nutrient concentrations are often cited as contributing to nuisance plant growths and associated water quality problems. This has led to several programs, strategies, publications and reports aimed towards developing nutrient criteria or guidelines for inland waters (e.g. ANZECC 1992; Bowles 1982). These undertakings either recognise the individuality of each water body and its consequent need for individually assigned criteria, or else provide a very broad range of values which will cover most water types and situations. Although all water bodies are individual, catchment managers seeking a specific target for nutrient concentrations need to be provided with guideline values. These targets cannot be assigned individually to every water body within Victoria. A more practical method involves the grouping of water bodies with similar environmental characteristics and assigning guidelines which reflect these characteristics. Many important environmental influences upon water bodies - such as climate, soils, topography and land use - are readily delineated at a regional scale. This enables allocation of water bodies into regional groups and subsequent preparation of nutrient guidelines for those regions. This approach provides a useful starting point, allowing regional or individual refinement of guidelines for streams as more data are gathered. The immediate impetus for the preparation of this document has come from the Nutrient Management Strategy for Victorian Inland Waters (Government of Victoria, 1995). A core component of the Strategy is the role of local and regional communities in the co-ordinated management of catchments, including the preparation of Catchment Nutrient Management Plans (CNMPs). The preparation of CNMPs will be greatly assisted by the provision of achievable yet ecologically meaningful nutrient guidelines. Provision of guideline concentrations for use in the preparation of CNMPs is an Environment Protection Authority responsibility (Government of Victoria 1995). 1.2 Scope Nutrient guidelines ultimately focus attention on the management of point source and non-point source nutrient inputs to receiving waters. Nutrient management forms part of a larger goal of maintaining or restoring water quality which reflects ecological integrity and sustainability. The guidelines are therefore based on this ecological goal. High nutrient concentrations are only one of the problems facing catchment managers. Attainment of nutrient guidelines may not ensure protection or restoration of aquatic ecosystems. Therefore, nutrient management should be seen as one part of an overall catchment management strategy. The nutrient guidelines have been limited to rivers and streams, due to a lack of useable information of lakes and impoundments in Victoria. In addition, impoundments are typically managed for water supply or hydro electricity, with ecological integrity being compromised. Although lakes and impoundments are not the subject of this document, there is a need to consider the setting of nutrient guidelines for these water bodies. Many of Victoria's lakes are, however, grossly nutrient enriched. For example, nutrient concentrations in Lake Colangulac resemble those in secondary treated sewage effluent (Metzeling et al. 1993a). Many lakes are terminal