Protecting Investment in Modernised Irrigation Salinity Risk Mitigation in the Shepparton Irrigation Region Terry Hunter1; John Mansfield1; James Burkitt1; Carl Walters2

Partnership Acknowledgment This project is funded as part of the Goulburn Broken Catchment Management Authority Regional Catchment Strategy in the Shepparton Irrigation Region and is provided with support and funding from the Australian Government and Victorian Government. This project is delivered primarily through partnerships between the Department of Environment and Primary Industries, Goulburn-Murray Water, the Goulburn Broken Catchment Management Authority and other bodies.

Where is the SIR? You are here Located in Central Northern Victoria Major towns – Echuca and Shepparton. Land area 500,000ha - 300,000ha irrigated Major industries Dairying, Horticulture - Agricultural production at the farm gate valued at $1.2 billion

Addressing Salinity Risk in the SIR The Problem & Solutions in the Past What’s Changed New Understandings – Research Implications for irrigation management and what is being done to mitigate risk Question you may be asking is how does this presentation fit into the theme of Irrigation Practice. In the SIR Catchment it has been determined that salinity mitigation is pivotal to sustainable irrigation. This presentation is focussed what needs to be done to provide assurance that salinity risk won’t limit irrigation or undermine the substantial investment in the region in irrigation infrastructure. Just a note that there are other presentations at this conference on other works currently been undertaken to facilitate this investment I’ll touch on The problem in the past and the original solutions The changed drivers The research we’ve undertaken The finish with a summary of the implications for irrigation management and what is being done to mitigate risk

Wet Climate = Extreme & Inevitable Salinity Risk Late 20th Century During the late 1980’s when the Shepparton Irrigation Region Land & Water Salinity Management Plan was first developed, it was assumed that the wetter climate experienced over the second half of the 20th century in Northern Victoria would continue. Under that premise, the risk of salinity was extreme and inevitable. Wet Climate = Extreme & Inevitable Salinity Risk

SIR Land & Water Salinity Management Plan - 1989 Significant investment in Salinity Mitigation. 30 Year Plan to Implement Works & Measures On Farm Planning Surface Drainage Public Managed Groundwater Pumps Privately Operated Groundwater Pumps Monitoring Programs Community Involvement As a result significant government investment was made in the form of Whole Farm Planning, surface drainage, groundwater pumping and community engagement to protect the viability of the region.

Economic Impacts by mid 1990’s SIR Salinity History Economic Impacts by mid 1990’s 270,000 ha with watertables less than 2 m below NS 65,000 ha protected by groundwater pumps In current $ terms with no pumping Production losses due to salinisation estimated at ~$100 million/year Regional losses estimated at ~$400 million/year Water table less than 2m meant high salinity risks and waterlogging for horticultural crops Significant impacts and works. The SIRL&WSMP works & measures adopted (even though somewhat expensive) were vale for money given the potential regional losses. Approx $400 Million/yr

A Changed World 1. Drought & Flood 12 years or so of drought reduced the threat from salinity . Realisation that the wet trend wasn’t going to continue in the same way it had in the past and was predicted. Also floods – which resulted in a significant rebound of the water tables.

X axis percentile of 414 monitoring bores exceeding waterlevel Y axis – water level as depth below natural surface Insert – is a water table contour map showing the spatial distribution of waterlevels across the region - in the “red” areas waterlevels are less than 1 m

Wet summer

Wet summer

2013 – Below average rainfall 43% increase in irrigation deliveries between 2012 and 2013 biut no change in watertable - Irrigation on its own doesn’t cause Wt’s to rise – needs rainfal For 2014 – If have normal autumn spring conditions anticipate jump similar 2011-12 Very slow vertical drainage

The interaction between rainfall and waterlevel is demonstrated on this graph – The blue line is water levels in a sample bore from 1095 to 2013 (Depth below natural surface The green line is residual rainfall curve showing the trend in rainfall (doesn’t start at zero as part of a larger dataset)

A Changed World 1. Drought and Flood 2. Modernised Irrigation Delivery System & On Farm 3. Drivers Government emphasise on increased food and fibre production 4. Risk & Cost Understanding Perceptions 2. Modernised irrigation Water resources became priority – and saw large investment in modernising irrigation infrastructure. & Water recovery Two Major programs a) Connection program Investing more than $2 billion to develop a modernised water delivery network Funded by the Victorian Government, Commonwealth Government and Melbourne Water b) Farm water program Funding for on farm infractrure in exchange for water savings – in total $122 M to be invested for 35 GL of water transferred to the federal government 3. Drivers Talk to grow more with less water. 4. Risk & Cost The perceived risk changed dramatically as many assumed salinity as a risk had gone and therefore no need to invest in any more. No longer funding to implement on ground works. – No Drains or groundwater Pumps. And as the previous graph showed, the return to wetter period saw a significant rebound of the water table and therefore salinity risk but perceptions of many still not chnaged. So – New world/information forces us to reassess to understand what the real risk is.

Understanding Future Salinity Risk Salt & Water Balance Project (S&WBP) Understanding of water balance and salt mobilisation implications under variable climatic and water management regimes Development of adaptive management systems and “triggers” for salinity and shallow groundwater resource management Harmonisation of salinity management and shallow groundwater resource management Project began in 2009. Is collaborative research project Led by GMW In conjunction with GBCMA, DEPI, University of Melbourne and CSIRO Conducted to understand the drivers of groundwater behaviour. To date over $1.6 million dollars has been invested. Led to development of adaptative management system Identified need for harmonisation There is 1000 privately owned groundwater pumps from which the pumped water is used for irrigation purposes. A number of these have been installed using government incentives to . provide salinity control Harmonisation is about trying to ensure pumps will be operated when required for salinity management. Landholders may need to be encouraged to operate pumps when water tables are high and there is a high salinity threat as normally surface water is cheap and abundant.

S&WBP Outputs Hydrology Salinity Management Framework Confirmation of ongoing risk of high watertables Recognition that the future risk will vary over time & space – need adaptive management approach Rates of watertable rise & fall Confirmation of understanding of salinisation risk Linkage between high watertables & salinisation Use of saline water needs to appropriately managed Salinity risk management approach for privately pumped shallow groundwater Salinity risk management system to manage shallow watertables & on-farm use of shallow groundwater within a variable climate Hydrology - no detailed computer modelling, used the climate data – we’ve had the extremes and so can look at the existing data to understand how the catchment reacts to wetter & dryer periods. Both the Hydrology & Salinity components are complete – about to start on developing the Management Framework.

Adaptive Management Approach What we’ve come up with is an adaptive response where we understand the areas within the region where the highest risk remains based on past watertable levels, rate of change and the likely future irrigation footprint. The purple line is the management boundary where the salinity risk is deemed significant and requires a higher level of monitoring. Out side the boundary is lower level of monitoring. The green area is where productive irrigation is occurring and is at the highest risk, so that is where we will prioritise works

S&WBP Conclusions: Winter/Spring rainfall on a wet catchment main driver for watertable response – irrigation wets the catchment High watertables (and an associated salinity threat) likely in all situations except severe drought Improved irrigation management will help but impact is minor compared with irrigation/rainfall interaction The Land & Water Management Plan is sound, however the hydrological loading is significantly more variable than originally envisaged

Implications for Irrigation Management The groundwater from private pumps used for irrigation is generally between 500 and 4000 EC The use of the groundwater needs to be carefully managed by: Shandying (mixing with high quality water) Paddock rotation Matching irrigation to soil type Potentially remediating land (i.e Gypsum application) Transitioning from Regulatory Non regulatory approach with landholders managing their own risk Groundwater can be up to 20 000 EC but is not used for irrigation but can be pumped and discharged to drains, channels and evaporation basins.

Supporting Irrigators Agency focus on developing digital delivery channels to target irrigation landholders Targeted information on Managing brackish water Areas of salinity threat (e.g. risk maps) Groundwater level hydrographs Options for water table and salinity control

Questions?