Farm consultant Peter Hook, who is also chairman of the Hawea Irrigation Co, which provides most of the water, described it as the ''difference between chalk and cheese''.
It was an ''incredible transformation'' and had occurred relatively quickly, Mr Hook said.
In the foreground (No 1 in photo), is Devon Dairy Farms' second unit, which has about 200ha under pivot irrigation and a small area watered by a travelling irrigator. That unit would milk 700 cows eventually.
No 2 in the photo is Devon Dairy Farms' first unit, which is milking 350 cows this year. An underpass will be installed to allow the 40ha across the road to be milked next year.
Without irrigation the land owned by Devon Dairy Farms might carry three sheep per hectare, and would be ''virtually valueless'', Mr Hook said.
With irrigation the stocking rate was about 2.5 cows per hectare or 18 sheep.
Although Mr Hook did not foresee a massive increase in dairy farming in the area in the future - one limitation was the capital cost required - there was already a change from cropping and sheep farming to dairy support.
This winter, there would be more than 20,000 cows coming into the Upper Clutha area for grazing, Mr Hook said.
When the Hawea Irrigation Co's scheme was designed in the 1960s, it was for border dyke irrigation, which was a relatively inefficient way to apply water, he said.
Overhead irrigation, whether pivot, travelling irrigator or gun, was much more efficient and made better use of a limited resource.
In the Hawea Flat area, about five pivots had been installed in the past year and Mr Hook said that he knew of at least five more planned, while there were about four there previously.
