NATIONAL WATER COMMISSION WATERLINES i

Australian groundwater modelling guidelines

Sinclair Knight Merz and National Centre for Groundwater Research

and Training

Waterlines Report Series No. 82, June 2012

Waterlines

This paper is part of a series of works commissioned by the National Water Commission on

key water issues. This work has been undertaken by Sinclair Knight Merz and the National

Centre for Groundwater Research and Training on behalf of the National Water Commission.

Commonwealth of Australia 2012

This work is copyright.

Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission.

Requests and enquiries concerning reproduction and rights should be addressed to the Communications Director, National Water Commission, 95 Northbourne Avenue, Canberra

ACT 2600 or email bookshop@nwc.gov.au.

Online/print: ISBN: 978-1-921853-91-3

Australian groundwater modelling guidelines, June 2012 Authors: Barnett B, Townley LR, Post V, Evans RE, Hunt RJ, Peeters L, Richardson S,

Werner AD, Knapton A and Boronkay A.

Published by the National Water Commission 95 Northbourne Avenue Canberra ACT 2600 Tel: 02 6102 6000 Email: enquiries@nwc.gov.au

Date of publication: June 2012

Cover design by: Angelink Front cover image courtesy of Sinclair Knight Merz Pty Ltd

An appropriate citation for this report is: Barnett et al, 2012, Australian groundwater modelling guidelines, Waterlines report, National Water Commission, Canberra

Disclaimer

This paper is presented by the National Water Commission for the purpose of informing

discussion and does not necessarily reflect the views or opinions of the Commission. In

addition, see separate disclaimer for Chapter 7 on the acknowledgements page.

Contents Acknowledgements.................................................................................................................... ix Executive summary ....................................................................................................................x 1 Introduction.......................................................................................................................1

1.1 Overview ...............................................................................................................1 1.2 Structure of the guidelines ....................................................................................2 1.3 Need for and use of the guidelines .......................................................................3 1.4 What are groundwater models?............................................................................4 1.5 Fundamentals of groundwater and modelling.......................................................5 1.6 The modelling process........................................................................................11

2 Planning..........................................................................................................................14 2.1 Introduction .........................................................................................................14 2.2 Intended use of the model ..................................................................................15 2.3 Defining modelling objectives .............................................................................16 2.4 Initial consideration of investigation scale...........................................................16 2.5 Model confidence level classification..................................................................17 2.6 Defining exclusions .............................................................................................22 2.7 Review and update .............................................................................................23 2.8 Model ownership.................................................................................................23

3 Conceptualisation ...........................................................................................................24 3.1 Introduction .........................................................................................................24 3.2 The principle of simplicity....................................................................................25 3.3 Conceptualisation of current and future states ...................................................26 3.4 Alternative conceptual models ............................................................................26 3.5 Data collection, analysis and data checking .......................................................27 3.6 Developing the conceptual model.......................................................................28 3.7 Checking the conceptual model..........................................................................32 3.8 3D visualisation...................................................................................................33 3.9 Conceptualisation as an ongoing process ..........................................................34 3.10 Reporting and review ..........................................................................................35

4 Design and construction.................................................................................................36 4.1 Introduction .........................................................................................................36 4.2 Numerical method...............................................................................................37 4.3 Software ..............................................................................................................39 4.4 Model domain .....................................................................................................47 4.5 Boundary conditions ...........................................................................................53 4.6 Initial conditions ..................................................................................................54 4.7 Model construction..............................................................................................55

5 Calibration and sensitivity analysis.................................................................................57 5.1 Introduction .........................................................................................................58 5.2 Fundamental concepts........................................................................................58 5.3 Calibration methodologies ..................................................................................65 5.4 Challenges and solutions....................................................................................69 5.5 Sensitivity analysis..............................................................................................77 5.6 Verification ..........................................................................................................78

6 Prediction........................................................................................................................79 6.1 Introduction .........................................................................................................79 6.2 Predictive model time domain.............................................................................81 6.3 Modelling extraction from wells...........................................................................82 6.4 Climate stresses in predictions ...........................................................................85 6.5 Particle tracking ..................................................................................................86 6.6 Predicting pore pressures ...................................................................................87 6.7 Predicting groundwater responses to underground construction .......................87 6.8 Annual aquifer accounting models......................................................................90 6.9 Checking model results.......................................................................................90

7 Uncertainty .....................................................................................................................92 7.1 Introduction .........................................................................................................92

NATIONAL WATER COMMISSION WATERLINES iv

7.2 The concept of uncertainty..................................................................................93 7.3 Sources of model uncertainty .............................................................................95 7.4 Relation of model calibration to model uncertainty.............................................98 7.5 Common approaches for estimating uncertainty ................................................99 7.6 Communicating model uncertainty to decision makers ....................................103

8 Reporting ......................................................................................................................106 8.1 Introduction .......................................................................................................106 8.2 Staged reporting ...............................................................................................106 8.3 Target audience ................................................................................................107 8.4 Structure............................................................................................................107 8.5 Visualisation.......................................................................