Aggregated emissions of total nitrogen and total phosphorus to the Swan-Canning catchment, Western Australia A submission to the National Pollutant Inventory By P Kelsey, J Hall, B Quinton and D Shakya Department of Water December 2011 Aggregated emissions of total nitrogen and total phosphorus to the Swan-Canning catchment, Western Australia A submission to the National Pollutant Inventory By P Kelsey, J Hall, B Quinton and D Shakya Department of Water December 2011 Department of Water 168 St Georges Terrace Perth Western Australia 6000 Telephone +61 8 6364 7600 Facsimile +61 8 6364 7601 National Relay Service 13 36 77 www.water.wa.gov.au © Government of Western Australia 2011 December 2011 This work is copyright. You may download, display, print and reproduce this material in unaltered form only (retaining this notice) for your personal, non-commercial use or use within your organisation. Apart from any use as permitted under the Copyright Act 1968, all other rights are reserved. Requests and inquiries concerning reproduction and rights should be addressed to the Department of Water. ISBN (online) 978-1-921992-27-8 Acknowledgements Thank you to the Swan River Trust, Department of Agriculture and Food, Department of Environment and Conservation, Water Corporation and Department of Sustainability, Environment, Water, Population and Communities for help and support during this project. For more information contact: Peta Kelsey or Deepak Shakya, Water Science Branch, Department of Water. The recommended reference for this publication is: Kelsey P, Hall J, Quinton B & Shakya D 2011, Aggregated emissions of total nitrogen and total phosphorus to the Swan-Canning catchment, Western Australia: A submission to the National Pollutant Inventory, Department of Water, Western Australia. Disclaimer This document has been published by the Department of Water. Any representation, statement, opinion or advice expressed or implied in this publication is made in good faith and on the basis that the Department of Water and its employees are not liable for any damage or loss whatsoever which may occur as a result of action taken or not taken, as the case may be in respect of any representation, statement, opinion or advice referred to herein. Professional advice should be obtained before applying the information contained in this document to particular circumstances. This publication is available at our website <www.water.wa.gov.au> or for those with special needs it can be made available in alternative formats such as audio, large print, or Braille. Aggregated emissions of TN and TP to the Swan-Canning catchment Contents Summary .............................................................................................................................. vii 1 Introduction ........................................................................................................................ 1 1.1 The National Pollutant Inventory ........................................................................................ 1 1.2 The catchment .................................................................................................................... 1 1.3 This study ........................................................................................................................... 2 2 Catchment description ....................................................................................................... 7 2.1 Location .............................................................................................................................. 7 2.2 Climate ................................................................................................................................ 7 2.3 Geology, geomorphology and soils .................................................................................... 9 2.4 Hydrogeology .................................................................................................................... 15 2.4.1 Description of the hydrogeology ........................................................................................... 16 2.4.2 Ellen Brook hydrogeological study ........................................................................................ 19 2.5 Hydrology .......................................................................................................................... 21 2.6 Land use ........................................................................................................................... 25 3 The Streamflow Quality Affecting Rivers and Estuaries model ......................................... 28 3.1 Description ........................................................................................................................ 28 3.2 Input data .......................................................................................................................... 32 3.2.1 Meteorological data .............................................................................................................. 32 3.2.2 Spatial data ........................................................................................................................... 36 3.3 SQUARE calibration for the Swan-Canning coastal catchments ..................................... 53 3.4 Confidence assessment for modelling outputs ................................................................ 57 4 SQUARE modelling results .............................................................................................. 63 4.1 Current catchment condition............................................................................................. 63 4.1.1 Average annual flows and loads ........................................................................................... 63 4.1.2 Annual delivery of nutrients................................................................................................... 66 4.1.3 Seasonal delivery of nutrients ............................................................................................... 68 4.2 Sources of nutrients .......................................................................................................... 73 4.2.1 Nutrient loads by subcatchment ............................................................................................ 73 4.2.2 Nutrient export by land use (source separation) ................................................................... 78 5 Knowledge and data gaps ............................................................................................... 83 5.1 Data for model calibration and validation ......................................................................... 83 5.1.1 Flow calibration ..................................................................................................................... 83 5.1.2 Nutrient calibrations .............................................................................................................. 84 5.2 Monitoring of urban developments ................................................................................... 84 5.3 Groundwater inflows ......................................................................................................... 85 5.4 Point source data .............................................................................................................. 85 6 Discussion ....................................................................................................................... 87 6.1 Comparison with previous NPI aggregated emission estimations (Deeley & Lindhorst 2000) ................................................................................................................................. 88 7 Conclusions ..................................................................................................................... 93 Appendix A Aggregated emissions data ....................................................................... 94 References ........................................................................................................................... 96 Department of Water iii Department of Water Tables Table 2.1 Groundwater use in Perth for 2004 (Davidson & Yu 2006) ......................................... 15 Table 2.2 Groundwater use (Davidson & Yu 2006) ..................................................................... 15 Table 2.3 Catchments of the Swan and Canning estuaries used for reporting of results ........... 22 Table 2.4 Dams on the tributaries of the Swan and Canning rivers ............................................ 23 Table 2.5 Land-use areas in the Swan-Canning coastal catchments ......................................... 27 Table 3.1 Leaf-area indices (LAI), percentage impervious area and percentage deep-rooted vegetation for land uses in the Ellen Brook catchment ............................................... 37 Table 3.2 Leaf-area indices (LAI), percentage impervious area and percentage deep-rooted vegetation for land uses in the Swan-Canning coastal catchments ........................... 38 Table 3.3 Annual nitrogen and phosphorus fertilisation rates for the urban catchments ............ 40 Table 3.4 Monthly fertilisation application in the Swan-Canning urban catchments as a percentage of annual amount ...................................................................................... 41 Table 3.5 Annual fertiliser rates for non-surveyed diffuse land uses in the Ellen Brook catchment. ..................................................................................................................