Return to list
SEVERE WATER STRESS CAN ALTER THE COMPONENTS OF THE HARVESTED GRAPE, DELAY RIPENING AND LEAD TO A LOSS OF PRODUCTION DUE TO THE SHRIVELLING OF THE BERRIES

In viticulture (grape vine cultivation and wine making), the term Irrigation has a negative connotation and in “old” Europe it was often associated with high yields and thus the wines would be of low quality. Irrigation has long been considered to be the preserve of the vineyards of the New World, but global warming is bringing about a change of attitude among more traditional vine growers.

 

In France, the recorded droughts of 2003, 2005 and 2006 have had an enormous impact on the wine-producing industry in the south of the country. Over the last thirteen years, the wine producers of these regions have been faced with severe constraints on the amount of water available for some of their fields. Yet severe water stress can alter the components of the harvested grape, delay ripening and lead to a loss of production due to the shrivelling of the berries.  These problems have resulted in the number of hectares under grape vines in the country dropping to 788,000 ha, i.e. 11% less than in the year 2000, this decline being even more noticeable in the Rhône valley and the region of Provence, particularly in Languedoc-Roussillon.

As a result of these events, the public authorities have decided to amend the laws prohibiting the irrigation of AOC wines (those labelled with a controlled designation of origin). The irrigation of these AOL wines is still forbidden, but a decree that appeared in the official gazette of 4th December 2016 specified the legal context under which this general rule could be waived:

• Irrigation is not allowed for any wine grapes between 15th August (or the onset of ripe­ning/veraison) and the harvest.

• In the case of the production of house or table wines, irrigation can take place before 15th August or the onset of grape ripening.

• For the controlled designation of origin wines, irrigation is authorised after the harvest and up until 1st May. However, the restriction may be lifted between 15th June (or flowering) and 15th August or the onset of ripening). Therefore, the AOC defence syndicate concerned may submit a request with the Director of the National Institute controlling the quality of the AOC label (INAO) for the possibility of using irrigation. Thus, this request must be accom­panied by the technical references established from a set of represen­tative plots used for producing AOC wines, proving the existence of water stress. A declaration of irrigation made to the INAO must obligatorily be prepared, describing the plots to be irrigated, irrigation dates and the system used. Checks can be made in order to verify, in particular, that the production load is not excessive and that in no case will it exceed the basic yield.

For some time now, irrigation has become the talking point of politicians and syndicates in the south of France.

The message is clear: the profitability and, therefore, the sustainability of the vineyard will not be possible without water. Nowadays, Languedoc-Roussillon is the main region for irrigation in France with 23,000 hectares of vines benefitting from the application of irrigation water, i.e. 10% of the region’s vineyards. This area is going to increase in view of the successive droughts that have hit the wine-growing regions. The main challenge at the present time is being able to take advantage of the region’s water project, Aqua Domitia, which aims to transfer water from the Rhone all the way to Béziers and Narbonne. The winegrowers are recognising the need to implement a project involving the construction of secondary networks in order to be able to benefit from this new water resource. This Project, developed by the Languedoc-Roussillon Region within the framework of the Regional Public Water Service, consists of bringing a second supply of water to the areas, thus providing water security for the generations of the future. It aims to complement the Regional Water Supply Network by interconnecting the networks supplied by the Rhône with those fed by the Orb, Hérault or Aude. The Project is already at an advanced stage with 3 large irrigation areas being supplied with water in 2015 and 2016: the Beziers (1500 ha) and North Gardiole (500 ha) areas in 2015; and the North Sommière irrigation zone, which had 500 ha supplied with water in early 2016.

 

In Italy, the rules and regulations are much more flexible than in France

In Italy, the world’s leading wine pro­ducer, shoulder to shoulder with France (44.4 million hl produced in 2014), wine growing is characterised by a multiplicity of different regional-type wines. For some, this diversity shows the variety and authenticity of Italian wine production. For others, though, it is perceived as an obstacle for the emer­gence of a vineyard of consistent quality.

Nowadays, it is still the case that 60% of Italian wine production comes from small-scale family farms, not specia­lising in growing grapes, especially in Sicily.

The average size of an Italian holding is 1 hectare, while it is 7 hectares in France and 20 hectares in Australia, but we can find vineyards in Tuscany of more than 20 hectares and tiny farms of less than 1 hectare in Sicily.

There are 20 wine-producing regions in Italy, the main ones being the southern-most areas such as Sicily and Puglia, these two accounting for more than 25% of national production with 30% of the vineyards. The regions producing the higher quality wines are located in the north and centre of the country: in Piedmont, Tuscany and Veneto, these three alone producing 50% of the country’s DOC (controlled designation of origin) wines.

The controlled designation of origin wines in Italy are called DOC (Denominazione di Origine Controllata) and DPCG (Denominazione di Origine Controllata e Garantia – Controlled and Guaranteed Designation of Origin): whereas the IGC (Typical Geographical Indication) label represents an intermediate level between the table wines and the DOC. These are often wines of a certain quality, which do not entirely comply with the requisites of a DOC product. Finally, at the bottom of the scale, we have the VDN (sweet natural wines) and the table wines.

Following a number of particularly hot and dry vintage years, such as 2012, which has been described by many as a really bad year, comparable with the 2003 vintage year, the heatwave year in Europe, a legislative decree appearing on 19th April 2013 authorised the irrigation of the grape vines (where not specifically forbidden by local legislation) in the case of droughts or extreme heat in the DOC, DOCG and IGT classified regions, which covers all of the main wine-producing areas of Italy.

Nowadays, no less than 26% of the vineyards producing wine grapes are irrigated, 85% in Tuscany, 50% in Veneto, 72% in Friuli, 34% in Emilia-Romagna, 43% in Puglia and 25% in Sicily. Irrigation is permitted in 30 AOC vineyards.

 

Climate change is in the process of transforming the Iberian Peninsula into a semi-desert region

In terms of the total number of hectares, the French wine industry has never been the largest in the world; rather this accolade belongs to Spain: i.e. 1,021 mil­lion in 2016, or 25% more than the French or Italian wine-growing regions.

However, the yields of the Spanish vineyards have always been very low: 22 hl/ha on average (until 1996), compared with 60 hl/ha on average in France. These low yields are caused by the restrictive water stress associated with a lack of available water resources. In fact, in most of the wine-growing areas in the north or south of the country, with the exception of Galicia, the Basque country or Catalonia, an­nual rainfall rarely exceeds 450 mm. Climate change is gradually turning the Iberian peninsula into a semi-desert region.

Vines benefit from plenty of sunshine, as all wine growers are only too aware. But too much heat is not conducive towards the proper ripening of the grape. Heat stress rapidly leads to an increase in the grapes’ sugar content, while the pheno­lic compounds, which give the wine its flavour, consistency and colour, will develop more slowly.

Thus Spanish wine-growers have to choose between harvesting the grape early and producing a wine with a good alcohol level, but still “not fully matured” or delay the harvest and have grapes rich in sugar which makes good wine, albeit with a very high alcohol content. The vineyards often decide to delay the har­vest… so the wines produced nowadays contain 14, 15 or even 16% alcohol, compared with 12% previously.

The government has, therefore, decided to modify the rules and regulations relating to the irrigation of wine grapes in Spain; since 1996, the irrigation of grape vines is routinely authorised (as Europe leaves this to the full discretion of the Member States). A lot of progress has been made over the last twenty years as, today, 29% of Spanish vineyards are irrigated. The average yield has increased from 23 hl/hectare to 36 hl/hectare.

In view of the scarcity of water in the country, drip irrigation is the preferred system used and represents 86% of the total area of irrigated grape vines. The irrigation water is generally supplied from boreholes sunk at variable depths. For example, in the very arid wine growing area of La Mancha, there are boreholes of 100 metres in depth. This is deep, but not inaccessible… However, the fuel cost makes pumping, and thus irrigation, very expensive. Irrigation is governed by laws relating to water resource allocation and water rights and the systems are equipped with meters. In La Mancha, for example, the rationale used for calculating the amounts applied, based on weather conditions and the physiological state of the vine, appears to be quite haphazard.

Another factor considered by the Spanish authorities is altitude. In the higher regions, the grape vines suffer less from the heat. The nights are cooler, allowing for a more harmonious ripening of the fruit. Historically grape vines have always been planted on hillsides. In the 1980s, mistakes were made and they were planted any old where, as happened in particular on the plains of La Mancha.

 

The irrigation of the grape vine is not necessarily synonymous with high yields and inferior quality. A well-designed irrigation system has a direct impact on the physiological state of the vine, improving the balance of the plant, while reducing water stress and encouraging more regular production levels. Nevertheless, with regard to the concerns expressed about global warming, further additional methods have to be considered in order to conserve or increase the compe­titiveness of the sector and a lot of work is currently being undertaken to assess the possibility of adapting the vineyards to climate change by modifying crop husbandry practices, grape variety or the location of the plots.