Integrating environmental and irrigation water allocation under uncertainty

Dudley, N. Dr; Ph: (02) 6773 2420; Fax: (02) 6773 3237; ndudley@metz.une.edu.au

Arthington, A.H. Prof; Ph: (07) 3875 7403; Fax: (07) 3875 7615; a.arthington@ens.gu.edu.au

Research organisations: Centre for Water Policy Research, University of New England, Armidale NSW 2351; Centre for Catchment and In-stream Research, Griffith University, Kessells Road, Nathan Qld 4111

Collaborators: The Queensland Department of Primary Industries - Water Resources; Water and environmental agencies from the other mainland south-eastern states and the Murray Darling Basin Commission. These agencies will be part of a Liaison Group for the project.

Sponsors: LWRRDC, Land and Water Resources Research and Development Corporation; Queensland Department of Primary Industries - Water Resources.

Objectives:

1. To develop methods and models to improve the short and long term allocation of water resources between environmental in-stream flows and extractions from the stream for irrigation consumptive uses under highly variable, uncertain climatic environments;

2. To combine the skills and models of CCISR and CWPR researchers to obtain methods and models that integrate the management of environmental in-stream flows and irrigation management. These will be applied to the Barker-Barambah Creeks subsystem of the South Burnett valley in southeast Queensland;

3. To continue existing CCISR research on the definition of the streamflows required to achieve various levels of environmental quality in the Barker-Barambah subsystem;

4. To maximise the objectives of each of these use classes (in-stream flows and irrigation), subject to their respective water allocations, by integrating the supply side and demand side management of each;

5. To effectively distribute or transfer information on the methods, models and study area results to potential users or adopters of the information.

Methodology:

By integrating water supply and demand management, with demand including both environmental and irrigation uses, this project seeks to minimise and quantify the trade-offs between effectiveness of stream quality water supplies and the opportunity costs (ie irrigation benefits foregone) of those supplies. Allocating rights to percentage shares of reservoir capacity, reservoir inflows and downstream tributary flows to stream environmental quality managers will give them control over water supplies of their own. Their demand for water stems from the desire to maintain particular historical, or modified historical, river flows. Failure to satisfy these targets attracts penalties (or negative benefits) in the models that will vary according to the magnitude and timing of the failure (e.g. high penalty if flow patterns are disrupted during breeding seasons). The optimal dynamic (i.e. through time) balance of water supplies and demands will be achieved by a simulation/dynamic programming model to maximise the expected value of benefits over 80-90 years of historical data. This model will have a similar basic structure to those previously developed and used by Dr Dudley for the integrated management of irrigation farms and their capacity share of water resources.

Progress: Major achievements include development of the following generic methodologies for:

• developing Decision Support Systems for integrating environmental and consumptive water uses under climatic uncertainty;
• developing trade-off curves as a framework for aiding water allocation between environmental and consumptive uses;
• defining the "objective function" in the optimisation model;
• defining "environmental effectiveness" rather than a monetary measure of the achievement of environmental objectives in the trade-off curves;
• presenting each point along the "environmental effectiveness" axis of the trade-off diagrams in terms of more detailed summary statistics describing flow quantities and sequences;
• presenting three possible approaches for developing environmental flow options as the target for environmental protection: (a) "natural" flow regime as target; (b) "modified" flow regime compiled using Holistic or Building Block Methodology (BBM) approaches; and (c) defined "range of deviation" from natural flow regime;
• developing a 'draft' package of programs for analysing flow data;
• developing a skills base for starting to apply the methodology and models to other catchments and to extend their development in other situations;
• presenting a possible "model" for incorporation of the "real costs" of lost environmental benefits. e.g. maintenance of recreational fishing and water quality.

Period: starting date 1994-10; completion date1997-07

Status: completed

Keywords: instream flows; environmental water demand; irrigation water demand; integrated management, tradeoffs, opportunity costs; stochastic dynamic programming; simulation

Publications:

Dudley, N.J., Arthington, A.H., Scott, B.W., and van der Lee, J.J. (1998). Integrating environmental and irrigation water allocation under uncertainty. LWRRDC UNE19 detailed report, Volume 1 - Introduction and background, Centre for Water Policy Research, University of New England, Armidale, NSW ($10).

Athington, A.H., Thompson, C. and Scott, B.W. (1998). Integrating environmental and irrigation water allocation under uncertainty. LWRRDC UNE19 detailed report, Volume 2 - CCSIR's ecological methodology and research, Centre for Water Policy Research, University of New England, Armidale, NSW ($10).

Scott, B.W. (1998). Integrating environmental and irrigation water allocation under uncertainty. LWRRDC UNE19 detailed report, Volume 3 - CWPR's methodology and models, Centre for Water Policy Research, University of New England, Armidale, NSW ($10).

Scott, B.W., Arthington, A.H., van der Lee, and Dudley, N.J., (1998). Integrating environmental and irrigation water allocation under uncertainty. LWRRDC UNE19 detailed report, Volume 4 - Integration of CCISR and CWPR research, Centre for Water Policy Research, University of New England, Armidale, NSW ($10).