**1. Introduction**

Wine grapes are grown over a very wide diversity of environmental conditions. Originally, wine grapes were confined around the Mediterranean basin, but as humans spread around the world, these plants were able to conquer new habitats. Vineyards now exist in areas with Mediterranean climatic conditions (i.e. with relatively long, dry summers) in Europe, South America and North America but also in Atlantic regions in Europe and North America and in places with a similar climate in New Zealand. In recent decades, *V. vinifera* vineyards have been established in North Beijing and Washington State (USA) where winters are cold and even tropical areas in Thailand. This highlights the plasticity of *V. vinifera* cultivars, which have become adapted to very different climatic conditions, producing reputable wines and table grapes under most of them.

Along history, growers have been forced to choose those cultivars best adapted to the local availability of water, seasonal temperatures, the dry periods they must face, etc., increasing experience allowing the most to be made of each situation. Different training systems and cultivation practices have also been developed, striking a balance between plant, vineyard management and the environment and giving rise to different viticultural landscapes, some now recognized as part of the world heritage. This balance, however, can be altered when priorities change, perhaps driven by the desire to produce more, or because of a change in market conditions. Thus, an area might need to increase yields or open up new areas of sustainable production. Areas naturally suited to raising white wine grape varieties might suddenly need to shift to red, or the variety habitually grown may need to be changed due to customer demand. Under certain circumstances, newly imposed conditions can only be met sustainably by modifying the vineyard agrosystem, perhaps by introducing a different kind of trellising or canopy management or by introducing irrigation.

For a long time, the drought tolerance of grapevines meant irrigation was not contemplated as a viticultural practice. Indeed, it took hard work to overcome the prejudice that grapevines are not well suited to it. By and large, vineyards in growing areas brought into production in the last 50 years have been irrigated. In some traditional areas, however, irrigation was banned until some decades ago. Irrigation results obtained from vineyards under regional regulations (geographical indications), with limitations either to yield or bud load, for example, may complicate the discussions of irrigation as it often happens that irrigated vines cannot express the most of them when we are limiting their optimal performance under those new conditions and when they are harvested at the same date. This turned out that part of the industry felt that the best wines were produced under situations of severe water stress. The aim of irrigating wine grapes is not always to produce higher yields but to ensure the quality required for different products. For example, some grapes are grown with the intention of producing young wines, others are raised to make wines for ageing and yet others for making spirits, etc.; as a result, they require different irrigation regimens and different optimal yields and different harvest time. In recent times, attitudes are changing as irrigation studies have increased and irrigation management becomes ever more technically friendly and controllable, and the consequences of global warming are felt.

In the following paragraphs, a review of the effects of water status on yield, vine growth and must and wine composition is exposed, and results are explained taken into account the phenological stage and the berry growth stage at which excessoptimal-severe available water took place.
