The effect of changing irrigation strategies on biodiversity

Summary

The irrigation industry is facing substantial change that is likely to affect the quantity and timing of water supply, as well as the infrastructure involved in water delivery and use.

Managing these changes without further compromising environmental sustainability requires knowledge of how irrigation practices effect local and regional biodiversity, and the implications for biodiversity persistence of possible changes in policies, district water management and farming methods. This project will identify likely changes to irrigation practice, predict how these changes might influence biodiversity in irrigated regions, and explore strategies to ameliorate any negative effects of predicted changes.

Recent Activities

During Spring and Summer 2008 we will be working with landholders, the Ricegrower’s Association of Australia, and Murrumbidgee Irrigation to further develop conceptual models and hypotheses, collect and collate existing data, select appropriate study sites, and conduct a pilot study to finalise the design and on-ground methods. We anticipate that this process will be followed by an intensive data collection period in Autumn 2009.  We will also be involved in development of a Monitoring and Evaluation Plan for the project and selected communications activities.

Aims

The overall aim of the project is to assess the impacts of changed irrigation practices on native biodiversity at local and regional scales, using the irrigation districts of the New South Wales Riverina as a case study.

More specifically, the objectives are to:

• Identify likely changes to irrigation practices and patterns of water use through consultation with practitioners and stakeholders
• Review the available information (including published literature) on the biodiversity of the natural and managed ecosystems of the Riverina
• Predict the local and regional implications of changed irrigation practices for biodiversity persistence
• Collect, collate and analyse new and existing information on biodiversity responses to irrigation practices
• Predict the local and regional implications of changed irrigation practices for biodiversity persistence
• Identify strategies which may help ameliorate any negative impacts for biodiversity that may occur

Outcomes

The primary outcomes of this project will be:

• Improved understanding of the relationships between biodiversity and irrigation practices and the potential effects of change in black box depressions and deflation basins
• Strategies to ameliorate any negative effects on biodiversity of predicted changes to irrigation practices
• Incorporation of this improved understanding and the strategies identified into decision-making and management at irrigation policy, supplier and farm scales

This incorporation may include changes to on-farm management practices, improved landscape planning strategies, modifications to irrigation infrastructure designs, strategies for the management of drainage waters, and modified policies relating to water management that incorporate better outcomes for biodiversity (e.g. relating to timing, quantities of flow). The potential for the project to be influential will be high, but diffuse, due to the complexity of paths to outcomes. There are also time lags between new knowledge and outcomes that generally exceed the life of the project.

Background

Irrigated agriculture in Australia’s Riverina consists of a variety of industries - rice, cereal, pulse and oilseed production, as well as livestock. Rice is the dominant crop, and is reliant on irrigation water supply from the Murray and Murrumbidgee Rivers, supplemented in some cases by underground water. Riverina irrigators are currently experiencing unprecedented restrictions on production due to water shortages. The current drought, together with the ramifications of the NSW environmental flow legislation of 1997, has resulted in irrigators receiving only a fraction of their water allocations.

The Riverina’s irrigation industries have significantly improved water use efficiency over the past 20 years through research and improved irrigation layouts. Given recent climate change projections (Australian Greenhouse Office 2003), and increasing pressure on water supplies, the need for even more efficient use of irrigation water in the future is certain. Options for reducing water use are being implemented or canvassed at both the enterprise and supply scales. Examples include changes in the cropping mix at an enterprise level, reduction or cessation of flooding of rice crops, fewer crops and more efficient water use. At the regional scale, changes to the nature of supply channels are possible, while the application of more efficient techniques may result in less drainage being received in regional wetlands.

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