Most all modern vineyards are irrigated. Many older vineyards are dry farmed. Why?
Irrigating your grapes instead of relying only on what mother nature gives you is about control and consistency--and yields. So, of course, it's about money. There wouldn't be irrigation if there wasn't an economic reason for it.
|Vineyard in Alexander Valley with drip irrigation tubes|
It's not that irrigating vineyards is evil, but about doing it the right way. No doubt some farmers are pretty careless in their water use, but I expect that's about to change. Being smart in your watering is what's needed. When you irrigate, how much water you apply, and even the placement and size of the emitters matter. The vine trellising, the density of the vines, the soil, the local weather, and even the rootstock used all go into the calculation.
So fine, then we can figure out how to use less. What about using no water on a vineyard (dry farming)? It turns out you can't just turn the spigot off and expect the vines to survive. Most any suburban homeowner knows you want to deep water new plantings rather than just turn the garden hose on it for 30 seconds. Why? If all the water is near the surface that's where the plant's roots will grow--they will go to wherever the water source is. The plant then becomes dependent on that surface water. Grape vines are the same. They can go really deep in search of water if they have to, but the roots won't if they're getting lots of surface watering.
|Older, dry farmed vines in Dry Creek Valley|
Sonoma County is currently implementing a plan for all vineyards to be sustainably farmed by 2020. Part of that will be only using the water you have available.
An article from Dan Berger on weaning vines off water
An article from the L.A. Times on the forgotten art of dry farming