The water footprint (WF) is an indicator that measures the amount of water used and polluted to produce each of the goods and services we use (volume/ time). It can be calculated for a process, a product’s entire value chain, a business, a river basin, a nation, an individual person or community of consumers. It has three components: green water footprint (rain water stored in the root zone of the soil and evaporated, transpired or incorporated by plants), blue water footprint (water that has been sourced from surface or groundwater resources and is either evaporated, incorporated into a product, changed from one water body to another or returned at a different time) and grey water footprint (amount of fresh water required to assimilate the load of pollutants to meet specific water quality standards). For this project, the footprint of an average consumer in Spain was calculated. The type of diet, habits, activities, consumption of products, and country of origin have an impact in the accounting of an individual’s footprint. The footprint is composed of both direct and indirect water use. The direct water footprint is the water that a person uses and pollutes directly in activities such as taking a shower, washing the dishes, watering a garden, flushing the toilet, etc. To calculate it, the minimum flow of different appliances and an assumed frequency and duration of every activity was considered. The direct water footprint calculated was 226 m3/year. The indirect water footprint is the water use associated to the production of the goods and services used by the consumer. The indirect footprint was calculated for an average Spanish diet and other consumptions like clothing, footwear, tobacco and books. The footprints for many of the products consumed by a Spanish person have already had their footprint accounted through numerous studies, but for some of the consumptions the footprint had to be calculated using different methodologies obtained from the Water Footprint Assessment Manual. For the diet component of the footprint there were three food products that had theirs calculated. The first methodology used was for the green, blue and grey footprint of growing a crop. This calculating methodology was previously tested comparing the footprint for bananas grown in Morocco, given in a previous study, with the calculated footprint of bananas grown in Islas Canarias. The testing showed the variablility of the outcome, given different climatological and crop parameters. The crop chosen to calculate its footprint as part of the Spanish diet was the melon. The second calculating methodology was used to calculate the footprint of producing fish through acquaculture, which considered the feed-related footprint and the water evaporation and infiltration from the ponds. The third product considered was pastries, which considered all the possible pastry compositions varying the ingredient proportions and the type of fat used. The footprint associated to a Spanish diet amounted to 1,839 m3/year.For the other consumptions an average Spanish person has on a yearly basis, the calculation was made adding the individual footprint for each material, taken from various studies, in adequate proportions for each product. The total footprint for the assumed yearly purchases of clothing, footwear, tobacco and books was 123.13 m3/year. Considering the direct and indirect water footprint for an average Spanish consumer the total calculated was 2.188 m3/year. The indirect footprint had the biggest impact on the total, contributing with 1,962.13 m3/year. The food group with the largest footprint was farm animal meats, which includes pig, bovine, poultry and goat meat and offals, with 515.65 m3/year, and the single product with the largest contribution to an average Spanish person’s annual footprint was pigmeat with 303 m3/year. Making changes in habits, diet and other consumptions can have a significant impact on reducing one’s water footprint. However, it has to be taken into account that when reducing the consumption of a product there is an associated increase in the consumption of a substitute, which changes the location of the footprint but does not necessarily reduce it. Hence, when the aim is to reduce our footprint, it is important to compare the alternatives to see if it entails an actual significant reduction.

Màster d'Enginyeria Ambiental, Facultat de Química, Universitat de Barcelona, Curs: 2019-2020, Tutor: Jaume Giménez Farreras