Traditionally, in Australian terms, the quality of wine has been related to the use of irrigation. If your particular vineyard was irrigated, then your product was known as irrigated, and therefore, inferior. This caused wild fire in the bellies of various wine makers and consumers alike. You couldn't make good wine from irrigated grapes.
This, of course, is almost as silly as saying that good wine is only produced from dryland fruit. From the growers point of view, being paid by weight, irrigation made a lot of sense. The practice of giving a vineyard a good old fashioned soaking just before vintage, meant that the grapes swelled as the vines pumped up the abundant moisture.Was this another case of turning water into wine? From the wine makers point of view at least, it felt like a case of the grower turning water into money, a much more serious offence.
So what is the real position? When it is all added up, it is simply a matter of grapes for the ground. A good vine will produce good fruit if it is happy. Grapes are a fruit crop, and like all fruit, even olives and dates, sufficient water during the growing season is essential to produce quality at harvest.
Now, where the plant gets this moisture from, is really what the argument is all about. Grow your grapes in a deep clay-loam in a winter rainfall region and (provided the rain doesn't fail), the vines will be productive. Grow them in a summer rainfall area, again provided the rain doesn't fail, and you'll have a good crop of fruit. Disease may be a problem there, but all things being equal, the vines will perform.
You can even turn on the tap. Irrigation, properly applied, is insurance against the variation in the weather. A timely drink can make the difference between a successful crop, and an ordinary one. In extreme cases, it can make the difference between a vintage and no fun at all.
But what happens if there is a shortage of water at critical growth phases, say, bud-burst or flowering or veraison. What can a grower of non irrigated vines do?. Ensuring a weed free vineyard throughout the season will conserve valuable moisture. Mulching along the vine row, not only provides valuable organic material which will trap moisture and carbon where it is needed, but adds considerably to the general microbiological activity and diversity of vineyard flora and fauna.
And if it gets really dry, as it is as I write this, you have two alternatives. Number one is to pray, but, at present, with the world the way it is, there’s a bit of congestion on the lines. The second, if you don't get through, is as follows. Arrange for a paid delivery of drinking water and then begin washing your car. That way you’ll succeed in stopping the trees following the dog around.