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Mapping Groundwater Quality in the Shepparton Irrigation Region

Note Number: GW0025
Published: 2002.
Reviewed: May 2008

Introduction

The Shepparton Irrigation Region Groundwater Management Plan (SIRGMP) was introduced in July 1999 to ensure groundwater resources are managed in anequitable and sustainable way. The SIRGMP encourages regular and responsible pumping of groundwater for salinity and watertable control in both wet and dry years. The plan also protects the rights of the groundwater user to access the resource.

As part of the licensing agreement under the SIRGMP, groundwater users are asked to provide an annual sample from their bore for salinity analysis. The information provided helps identify salinity hot spots and variations across the region from one year to the next. This allows groundwater users and extension staff to adopt the most appropriate management strategies to minimise declines in pasture productivity, soil structure, animal health andcorrosion of equipment.

For more information of the effects of groundwater refer to Groundwater Note GW0027: Using saline groundwater in the Shepparton Irrigation Region.

The importance of monitoring groundwater salinity

Monitoring of groundwater quality within the SIR on an annual basis enables:

  • Landowners to track changes and trends in groundwater salinity over time on both an individual and regional scale.
  • Landowners to match the salinity of their groundwater with a suitable end-use to minimise adverse impacts on pasture quality, soil structure, animal health or equipment.
  • Extension officers to provide more targeted, focused information to groundwater users on issues specific to each property, enabling users to get the most out of their groundwater.
  • Identify areas where groundwater is too saline to be safely used for irrigation or stock drinking water, but which may be suitable for the Public Groundwater Pump scheme.

Salinity of groundwaters in the SIR

The groundwater quality of private shallow bores in the SIR for the 2001/2002 irrigation season has been analysed and mapped (Figure1). The map highlights the variation in groundwater salinity across the Region. Light green shading represents good quality groundwater found in Murray Valley east, areas surrounding Shepparton and Nathalia as well as the western region of the SIR. High salinity groundwater is found around Tongala, Kyabram, Stanhope and Tatura. These areas require careful management when used for irrigation and stock and domestic purposes.

Groundwater salinities for the SIR have been mapped according to the guidelines outlined in the Shepparton Irrigation Region Catchment Strategy as follows:

Up to 800 EC: The recommended safe reuse guideline for irrigation of white clover/ryegrass pasture on a Lemnos loam soil is 800 EC. Heavier soil types may require slightly lower irrigation water salinity to prevent a decline in pasture productivity.

800 - 1 700 EC: After 3 to 4 years of irrigation with 1 700 EC water, a 15 per cent reduction for a white clover/ryegrass pasture on a Lemnos loam occurs.

1700 - 3500 EC: Financial assistance is available to landholders with groundwater salinity less than 3 500 EC for the installation of a shallow bore. Blending of groundwater (with a salinity of 3 500 EC) with surface water is required at a 4:1 ratio

3 500 - 5 000 EC: Limited reuse potential of groundwater with salinity in this range due to the large mixing ratio of groundwater to surface water required to reach the recommended salinity reuse of 800 EC.

Greater than 5 000 EC: Investigation for the construction of a public groundwater pump is available in areas where salinity exceeds 5 000 EC. Public pumps provide watertable and salinity control for the community by pumping into channels (during peak flows) and drains (when certain conditions are met). Provision of groundwater for stock drinking water at this salinity threshold is not recommended for young, sick or pregnant or lactating cattle.

Note: The recommended reuse salinity for groundwater for irrigation in the SIR is 800 EC. It is suggested groundwaters with higher salinities should be blended with surface water supplies to meet this guideline.

For more information on the effects of saline water on pasture productivity, animal health and corrosion of dairy equipment refer to Groundwater Note GW0027: Using saline groundwater in the Shepparton Irrigation Region.

For more information contact Terry Batey, Groundwater Extension Officer, DPI Tatura. Phone 5833 5222.


Figure1: Salinity of shallow bores in the Shepparton Irrigation Region – 2001/2002 irrigation season. Classes are after SIRLWMP (1989). The information provided in this map is based on data collected annually from private bores in the SIR. The creators of this map do notwarrant that this map is definitive nor free of error and do not accept liability for loss arising from the use of this product beyond it'soriginal purpose.

Figure1: Salinity of shallow bores in the Shepparton Irrigation Region – 2001/2002 irrigation season. Classes are after SIRLWMP (1989). The information provided in this map is based on data collected annually from private bores in the SIR. The creators of this map do notwarrant that this map is definitive nor free of error and do not accept liability for loss arising from the use of this product beyond it'soriginal purpose.


Acknowledgements

Thanks to the Natural Heritage Trust, Goulburn Broken Catchment Authority and the Department of Natural resources for providing funding for this project

This Information Note was originally developed by Melinda Beth and was previously published in November 2002.