Irrigating vineyards with brackish groundwater

The reduced water allocations and increased prices faced by Lower Murray irrigators through the Millennium Drought prompted interest in alternative water supplies to help vineyards remain viable. Brackish groundwater is an additional supply option that can be used for supplementary irrigation. In 2022 a vineyard in Langhorne Creek invested in the construction of a holding dam and pumping infrastructure to enable ‘shandying’ of their brackish groundwater with less saline, but drought-susceptible (in both availability and price) River Murray water. This offered a unique opportunity for SARDI to evaluate the potential to use water sources of different qualities. Vineyard metrics were integrated into numerical models and the long-term impacts of irrigation scheduling strategies were assessed, including volume, quality, and timing of use of the dual water sources. The aim was to optimise management strategies so that the use of the more readily available and less expensive groundwater could be maximised in a sustainable manner.
Sixteen modelling scenarios were assessed and included four water quality levels, two climates and two irrigation schedules. Numerical models suggested that the low-salinity river water remained the most sustainable option for maintaining non-saline, productive soils in Langhorne Creek. Modelling suggested that supplementing irrigation with brackish groundwater may present an opportunity to maintain production during periods of reduced river water availability (and/or low rainfall) if used as a blended or cycled supplement to the better-quality river water. Adoption of more saline irrigation options would necessitate diligent monitoring of rootzone salt accumulation and would likely require targeted leaching events to limit the risk of irrigation-induced salinity.