WINETECH Technical Yearbook 2019

CAREN JARMAIN: Independent researcher KEYWORDS: Grapes, wine, water footprint. JANUARY 2019 WATER FOOTPRINT OF GRAPES AND WINE

During the past season, with many people living in the Western Cape trying to survive with a mere 40 to 50 L of water per person per day, many figures were quoted reminding us just how much water is commonly used in our daily living. For example, that about 19 L of water is used for a 90-second shower and that one flush of your toilet will use 9 L ( www.thesouthafrican.com ). Many people were also surprised to realise just how much water they “consume” through eating their daily food. For example that it takes 132 L of water to produce a single cup of coffee (125 ml), 196 L for a large (60 g) egg and 18 L of water for a slice of bread of 30 g. For supper, your 200 g steak will cost you 3 083 L of water and your small (125 mL) glass of wine 109 L ( www.project-platforms.com ). But the question is: what do these values really mean and do they matter?

These values also referred to as a “water footprint (WF)”, provide a measure of the amount of water used to produce each of the goods and services we use – whether your favourite fruit, a glass of wine or pair of jeans. Because of the nature of goods and services, a WF can be expressed in different ways, for example, a litre of water used per kg of crop produced (L/kg), but also a litre of water used per unit of currency derived (L/R). WFs considers both direct and indirect water uses and are sometimes expressed in its colour components: green, blue and grey. Let me explain. For example, the 109 L of water used to produce your 125 mL of wine will take into account all water used right from the production of grapes on the farm (e.g. rainfall and irrigation) all the way to the cellar (e.g. harvest container washing, winemaking processes, cooling and cleaning), but even beyond that, all the way up to the recycling of your wine

bottle. Indirect water uses considered will include the water used in the production of electricity, fuel, the wine bottle, labels and others. The colour classification refers to the origin or impact of the WF. For example, the green water component will represent the rainfall which ends up in the soil and is used to grow the grapes. The blue water again will represent all “physical” water used (for example for irrigating the crops) and which is extracted from streams or groundwater. The grey water component represents something very different to that which we consider grey water at home. The grey water fraction here is the volume of water required to dilute “polluted” water back to an acceptable standard for an area. Grey water is typically the result of on-farm chemical application or waste water generated in a process, such as making wine.