THE Murray-Darling wine region continues to be the engine room of Victoria's almost $2 billion-a-year wine grape industry.

The Victorian Wine Industry Association's knowledge project found the region had the largest area of vineyards and was responsible for more than half of the grapes grown in the state but was home to a lower than average number of wineries.

Victorian Wine Industry Association executive officer Joanne Butterworth-Gray said the project - the first to quantify the value of wine and grape sales to the Victorian economy - found domestic sales accounted for a surprising 70 per cent of the $1.9 billion total.

The project also identified 820 wineries across the state, almost half of them on a "micro" scale - crushing less than 20 tonnes of grapes each year - which is equivalent to 1500 cases of wine.

Ms Butterworth-Gray said two-thirds of wineries had cellar doors, which made them heavily reliant on regional tourism.

"A lot of these small businesses see themselves as quite profitable. "It's just their scale is so tiny. Some businesses' gross revenue is only $30,000, but that doesn't mean they're not profitable in their eyes."

The project also revealed a greater-than-expected trade of grapes between regions, particularly from the state's northwest to larger wineries closer to Melbourne.

Ms Butterworth-Gray said this was significant because it showed the dependence of many companies on inland fruit.

One example was Littore Family Wines, which grows some of its wine grapes at Moorabool, but trucks in the majority of fruit from Sunraysia vineyards to its $20 million winery northwest of Geelong.

After crunching the numbers, brothers Vince and David Littore decided to invest in infrastructure near a port and transport their grapes rather than moving the bottled wine.

Ms Butterworth-Gray said the research project would continue this year in order to keep up with changes.

"In an industry that's going through a lot of challenges and potential restructure, it's very important to be able to benchmark and identify movements in the industry," she said.