A real Cape Winelands winter is about much more than a roaring fireplace and a slow-cooked curry washed down with a good red while taking in the stark beauty of bare vineyards. Putting aside all these romantic notions of winter, low temperatures accompanied by plenty of rain are very important to vines.
After three consecutive years of short winters and the much-debated low rainfall, Cape vineyards are in dire need of proper winter conditions. The physiological changes vines undergo during their winter hibernation are interesting – the low temperatures, shorter days and adequate rainfall play an important role in the eventual quality of the wine grape harvest. But with the vines in dormancy, what actually happens to the winter rain?
During winter, vines in their resting phase don’t absorb any of the much-needed water. Even existing cell water moves to an intercellular area to protect the plants from damage should the water freeze at low temperatures. Winter rainfall is however crucial as it replenishes ground water and summertime irrigation resources such as dams and rivers. In our prayers for rain we might add a request for it to be slow and steady. Too much water at once washes away soil nutrients, damages contours and stresses vines – even in their resting phase.
Threats of Day Zero have made us much more aware of the importance of sustainable water usage and saving in times of plenty. When the winter rains eventually come and hope flares that gardens will recover, responsible water usage should stay top of mind. Being water-wise should not only apply to special seasons and during dire conditions.
It takes about seven litres of water to produce one litre of wine, so the importance of water in the Cape Winelands is about much more than moisture for vineyards. There’s this joke about drinking wine to save water, but there are other ways producers can be water-wise. These include:
l Use mulching to encourage rainfall infiltration and reduce runoff.
l Employ a demand irrigation system using automatic soil moisture probes and leaf moisture meters (tension meters) to determine plant needs.
l Replace microjet sprays with a microdrip irrigation system.
l Irrigate at night in summer to prevent evaporation.
l Regularly inspect and maintain all water supply and water distribution infrastructure.
l Use a computerised water-demand management system based on weekly soil and leaf moisture data and climatic information.
l Clear invasive alien plants and re-establish indigenous plants, especially next to water sources such as rivers.
l Fit nozzles to hoses used in the cellar.
l Use a cellar system that disinfects incoming water. This ensures bacteria-free water to clean tanks and bottles and reduces the risk of contamination. It also extends the life of the bottling unit’s water filters and eliminates the need for strong cleaning agents to remove contaminants on the winery floor.
l Implement a system that improves the final treated effluent quality. It significantly reduces chemical oxygen demand (COD) in effluent and lessens the pollution risk from winery effluent.
l Use treated effluent water for irrigation and compost heaps.