Calculating the water footprint of buildings

Water is used at every stage of construction, especially so in the production of construction materials. Understanding how much of it has been used can lead to better conservation methods.
What is the water footprint of a building (Source: Wikipedia) What is the water footprint of a building (Source: Wikipedia)

Construction industry is a booming industry, with the real estate sector contributing heavily towards the country’s GDP. However, it is also very water-intensive consuming an enormous amount of fresh water. After agriculture, the real estate sector is the second largest employment generator in India. Thus it is important to understand the quantum of fresh water that geoes into construction materials as well as the fresh water that is used during the construction.

What is the water footprint of a building?

A research paper titled ‘Studies on Virtual Water Content of Urban Buildings in India’ published by the Indian Journal of Science and Technology, attempts to analyse the virtual water of sample urban residential buildings in Kolkata and Pune to arrive at a better understanding of the subject and establish its significance. These two cities were chosen as both have witnessed a tremendous growth in the building sector during the past decade, and they are also completely different in terms of their climate and water resources. While Kolkata falls in the hot humid zone with an abundance of water, Pune falls midway between warm-humid and hot-dry zone and belongs to a water stressed area which is totally rain dependent.

The research computes both the inherent virtual water, which is the water embodied in the major construction materials or the water used in the production of the materials, and the induced virtual water, which is the actual water used during construction work. The study restricts itself to five construction materials--bricks, cement, steel, aluminium and glass--due to availability of limited data. Data on quantity of material used and average water used per day on the construction site was collected from the sample sites for this study.

Virtual water: Water used to create the goods and services that we consume or use

The paper discusses that in both the buildings, and both in case of the foundation and superstructure, steel remains the highest contributor towards the inherent water of a building. This indicates that steel is the largest contributor to the inherent virtual water. The water used during construction was much higher for Kolkata than for Pune. The paper reasons that Pune being water stressed, there was conservative use of water, unlike Kolkata, where water was not much of a concern. Another aspect is the higher number of workers living onsite in Kolkata, which led to an increased demand for water. 

The paper calculates the total virtual water for the Kolkata buildings to be higher than that of the ones in Pune. Further analysis shows that the inherent virtual water of the materials of construction is more significant when compared to the induced virtual water. This means that the water embodied in the materials of construction is far more important than the actual water used during construction.  

Importance of virtual water 

The paper thus concludes that the choice of materials and the quantity plays a significant role in the virtual water content of buildings. Also, it finds that the induced virtual water quantity can vary significantly based on the availability / scarcity of water and the number of workers staying on-site. The average virtual water of the case studies translates to the operational water demand of 1233 families for one whole year, a significant amount of fresh water. The paper ends by stating that here is an urgent need to address the issue of pre-operational water management of buildings and carry forward this field of research to fill the missing links.

Please download a copy of the paper below.

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