Understanding and Reducing Evaporation Losses in the Northern Murray-Darling Basin

Reducing the amount of water lost through evaporation from small farm dams can be as simple as planting a windbreak or erecting a shade net. But for larger dams, like those on many cotton farms in the Murray-Darling Basin, irrigators are increasingly looking for more comprehensive and cost-effective solutions. With innovative new materials and technologies emerging all the time, One Basin CRC has joined researchers from the University of Southern Queensland, the University of Melbourne, and the Cotton Research and Development Corporation, to develop a comprehensive framework to help irrigators work out the most efficient solutions for their dams.

About this project

Earth tanks, gully dams, ring tanks, turkey nests – whatever name you give them, on-farm water storage has always been a distinctive part of Australia’s agricultural landscape, and a vital key to the success of irrigation in the Murray-Darling Basin. But in recent years, rising temperatures and shrinking water availability have led to growing concerns over the long-term costs of evaporation from nearly 2,000 dams that water farms in the northern basin.

Recent studies suggest that evaporative losses from dams in this region are 60% higher than the rest of the basin, with many – particularly exposed shallow dams – losing up to 45% of their total storage volume over time. This project aims to design a system for accurately quantifying evaporation from individual dams – through satellite and aerial imaging, weather and farm data – before conducting global surveys of the best mitigation measures for small storages (up to 20 hectares) and large dams (20-300 hectares). In its final year, the project will collate this information into a strategic framework to support commercial-scale demonstrations of the most effective technologies – and help farmers evaluate the best solutions for their dams.

With decades of research in water storage science, the project’s leads have amassed a wealth of knowledge on the most successful mitigation methods: from deep dams with reduced surface areas (expensive but efficient); to modular systems like ‘shade balls’; continuous ‘bubble-wrap’ covers (very efficient for small dams); polymer-based monolayers that form a film on the water’s surface; and floating solar panels (expensive but increasingly attractive for their revenue-generating potential).

Factoring in their efficacy, infrastructure and maintenance costs, and the current water price, alongside microclimate projections and considerations of water quality and impacts on flora and fauna, the project aims to provide irrigators with an accurate and rigorous framework through which to optimise their investments.

Outcomes

The first stage of the project aims to evaluate the scale of evaporative losses across the northern Murray-Darling Basin. Led by Professor Andrew Western, Chair of Hydrology and Water Resources at UoM’s Faculty of Engineering and Information Technology, the team is studying various methods for accurately measuring evaporative losses from farm dams in remote areas. From her base at One Basin’s Goondiwindi Hub, post-doc researcher Jia Xu is conducting a major assessment of water losses from 1,020 dams, using satellite sensing and on-farm data to quantify the amount of water in each dam and identify those that are losing the most to evaporation. The project is also recruiting a second post-doc researcher to undertake a technology review and assessment of globally available products and techniques to mitigate evaporative losses at scale.

The second stage will involve two literature reviews to canvas the latest global research on the costs and efficacy of technologies to address evaporative losses from small farm storages (under 0.2 km²) and large dams (up to 3 km²). The findings of these studies will be correlated with other information and irrigators’ experiences across the northern basin to inform a strategic roadmap or series of tools to help irrigators evaluate the specific challenges and requirements of their dams according to their size, construction, geometry, and usage. A decision on the best investment solution for each dam will be based on a correlation of its initial capital costs, maintenance needs, usage profile, projected evaporation savings, and cost returns over time.

This project promises the most comprehensive study of the measurement and mitigation of evaporative losses from farm dams ever conducted in the Murray-Darling Basin, in an effort to address one of the greatest challenges facing irrigated agriculture in Australia.