Assessing the Impact of Irrigation Efficiency Projects on Return Flows in the South-Eastern Murray–Darling Basin, Australia

Glen R Walker,Quan J Wang,Rob Rendell,Avril C Horne

doi:10.3390/w13101366

Glen R Walker, Quan J Wang + Show 2 more

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https://doi.org/10.3390/w13101366

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Journal: Water	Publication Date: May 14, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: South Australian Water Corporation, Bendigo Health

Abstract

Improving irrigation efficiency (IE) is an approach used globally to help meet competing demands for water and facilitate reallocation of water between sectors. In the Murray–Darling Basin in Australia, the Australian government has invested heavily in IE projects to recover water for the environment. However, this approach has been seriously questioned, out of concerns that improved IE would reduce irrigation return flows to rivers and therefore offset water recovery. In this study, we use a water balance model to assess the impact of the IE projects on return flows and highlight sensitivities and uncertainties. The model enables the impact on return flows to be assessed on specific IE projects and regional characteristics. Overall, reductions in return flows are estimated to be less than 20% of the total proposed IE savings. The history of IE in the southern MDB has meant that most of the current reductions are in ground return flows. Our estimate is much lower than two previous studies, mainly due to different assumptions being used on groundwater connectivity between irrigation areas and major streams. While the IE projects significantly reduce seepage to groundwater (with off-farm and on-farm projects reducing seepage by 19% and 53% of total savings respectively), not all seepage reductions will translate to a reduction in ground return flows to rivers. A lower estimate is consistent with existing monitoring and groundwater modeling studies. In this paper, the study results are discussed in a broader context of impacts of IE projects on volumes and salinity of streams and groundwater resources.

Highlights

Achieving the Sustainable Development Goals of the United Nations by 2030, and Goal 6 in particular will require significant investment in increasing irrigation efficiency (IE) and supporting water reallocation from agriculture to domestic and environmental uses [1,2,3]
This paper examines the south-eastern Murray–Darling Basin (MDB) in Australia, where concerns have been raised over large government funded water infrastructure projects aimed at reallocating water to the environment, while maintaining irrigation-dependent communities [14]
The results suggest that there is a limit to the cumulative reduction in ground return flows from irrigation areas that is possibly comparable to the estimates from III

Summary

Introduction

Achieving the Sustainable Development Goals of the United Nations by 2030, and Goal 6 in particular (sustainable management of water and sanitation for all) will require significant investment in increasing irrigation efficiency (IE) and supporting water reallocation from agriculture to domestic and environmental uses [1,2,3]. Given the importance of ensuring continued food production and economic and social viability for a growing population, focus has been placed on improving infrastructure and on-farm practices to allow the same agricultural production for less water, with water savings transferred to other uses [4]. The suggestion is that for a given amount of water diversion from a river to an irrigation scheme, more efficient irrigation generally leads to less return flow to the river [6,9,10,11]

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