Rainfall and Precipitation Timing

In the Riverland, Australia's largest winegrape region by tonnage, average annual rainfall for 2006 to 2025 was 254mm, with 148mm of that falling in the October to April growing season. Mendoza, Argentina's most important wine province by productivity, is a desert with around 200mm of rain a year. At the wet end, Rías Baixas, which sits right on the Atlantic, gets 1,600 to 1,800mm of rain per year across its areas.

The main drivers of vineyard water demand are solar radiation, air temperature, humidity and wind speed, working together with the vine canopy and the vineyard floor. The stage from fruit set to veraison uses about 35% of the vine's annual water, while veraison to harvest, when sugars accumulate in the berries, uses about 36%. Flowering and berry set are very sensitive to water stress. Checking soil moisture two weeks before budburst leaves time to fill the soil profile if winter or spring rain has fallen short. Too much rain just before harvest can make grapes swell, risking dilution or berries bursting on the vine and opening them to disease. Rain that splits berries often leads to direct infection of ripening fruit by botrytis, and high soil water during ripening may increase botrytis growth. Drainage is covered in its own WineWiki article.

• Vine water demand follows sun, heat, humidity and wind
• Irrigation is needed when rain and soil moisture fall short

In the Riverland, low relative humidity results in little or no disease pressure. A Wine Australia benchmarking project reviewed the irrigation practices of over 40 growers across the Riverland, Sunraysia and Riverina regions. Research there has measured Shiraz and Chardonnay water use to inform irrigation practice in the region. Higher growing season temperatures in South Australian regions have also led to water scarcities for irrigators. Mendoza gets its roughly 200mm through some summer storms, and Roberto de la Mota calls it "a really healthy viticulture." Mendoza's oases have water for farming thanks to the Mendoza, Tunuyán, Atuel and Diamante rivers. Albariño was traditionally trained on pergolas, which keep the grapes well away from the damp ground. Raising the vines allows greater airflow around the grapes, helping to reduce the risk of humidity and fungal disease in a rainy climate. In Rías Baixas, the stony, relatively infertile soils drain well, and Albariño's thicker skins give the grapes some resistance to fungal disease.

• Dry: Riverland and Mendoza
• Wet and ventilated: Rías Baixas

Where rain falls short, irrigation fills the gap: it is required when rainfall or existing soil moisture cannot meet the vine's water requirements. Before going without irrigation, growers should check whether rainfall is adequate and consistent enough to support a profitable non-irrigated vineyard. In dry climates, soils with high or medium water reserves may support vines with little or no irrigation. Where dry farming stops being viable, the recommended tools include drip irrigation, regulated deficit irrigation (RDI) and monitoring the plot's water status. RDI means restricting water for a set period, most commonly after fruit set, to control shoot vigour and berry size, which can benefit fruit quality. Its biggest limitation is the amount of water in the soil at the start of the season. Adequate drainage and vineyard floor management can prevent excess soil water, though this may be difficult in years with high and frequent rainfall. Slashing mid-row grasses can help draw water out of the soil.

• Dry regions: irrigation, including drip and RDI
• Wet regions: drainage and floor management

Primary sources: https://www.wineaustralia.com/market-insights/regions-and-varieties/south-australia-wines/riverland, https://www.wineaustralia.com/getmedia/4c434a71-6284-44d6-8e23-07e0e629ac0a/MI_Riverland-Region-Snapshot-2025-26.pdf, https://www.decanter.com/features/r-as-baixas-grows-up-245821/, https://www.wsetglobal.com/knowledge-centre/blog/2026/why-albari%C3%B1o-is-more-than-a-refreshing-summer-wine, https://www.decanter.com/wine/wine-regions/mendoza/mendoza-world-wine-capital-30632/, https://www.wineaustralia.com/getmedia/0d28f6c3-49f8-4865-8304-26d2f64bf977/Water-management-for-wine-grapes-in-a-drying-environment.pdf, https://www.oiv.int/node/3132, https://www.decanter.com/learn/how-to-understand-vintage-54305/, https://www.wineaustralia.com/getmedia/b78baaea-d1de-469f-a8aa-1aec30d4d756/201307-Botrytis-QA?ext=.pdf, https://www.wineaustralia.com/research_and_innovation/projects/incubator-initiative-how-does-phenological-stage-i, https://www.wineaustralia.com/research_and_innovation/projects/irrigation-benchmarking-in-the-murray-darling-basin. Last verified 2026-10-04