The water footprint of a product is calculated by adding up the unseen water - a concept known as "virtual water" - required for every stage of the production process.
A 1kg pair of jeans would have used 10,850 litres of virtual water, while a 250g T-shirt would have used 2,720 litres, based on a 2005 report The Water Footprint of Cotton Consumption.
GONE TO WASTE
For all the resources expended and pollution created, clothes may not last long in a typical wardrobe.
The lowest-priced garments could be tossed out after seven or eight wears, indicated a 2016 report by consulting firm McKinsey & Company.
A 2017 online survey of 4,097 Singapore respondents by research agency YouGov found that 73 per cent had thrown away clothes in the past year while 34 per cent had discarded an item after wearing it only once.
Local charity-run thrift shops are on the receiving end too.
The Salvation Army Red Shield Industries said clothing made up the bulk of its in-kind donations, which averages 10 tonnes daily during non-peak seasons. About 5 to 10 per cent of clothes donated came with price tags, said general manager Paul Chay.
The New2U Thrift Shop run by the Singapore Council of Women's Organisations said it did not track the volume of clothing donations but had noticed an increase in the quantity of donations in general. Programme executive Denise Balhetchet said "quite a number" of clothes came with price tags attached.
While donated clothes get a second lease of life, many other unwanted garments are binned.
Worldwide, a garbage truck worth of clothes is incinerated or left at a landfill every second, said a 2017 report by the Ellen MacArthur Foundation.
Singapore generated 219,800 tonnes of textiles and leather waste last year, with only 6 per cent recycled, based on National Environment Agency data.
Though Singapore incinerates textile waste and takes the ashes to the landfill, some countries leave clothes to degrade in landfills.
The amount of time taken for clothes to break down in a landfill depends on the material, or combination of materials, and its molecular make-up, said Republic Polytechnic's School of Applied Science programme chair (work learn programmes) Jeremy Kong.
His estimates vary from two weeks to five months for 100 per cent cotton textile to completely break down, one to five years for wool and 200 years upwards for polyesters, which is made up of synthetic polymers.
ARE CHANGES AFOOT?
The fashion industry itself is responding, said industry experts.
Dr Lee Kyung Mi, course chair of diploma in apparel design and merchandising at Temasek Polytechnic School of Design, said sustainability is also taught in curriculum, adding: "Sustainability is a key issue and one of the biggest buzzwords in the fashion industry today."
A growing number of clothing and apparel brands have joined the Zero Discharge of Hazardous Chemicals, a coalition aiming to do away with the use of harmful chemicals in their supply chain.
Since it started in 2011 with six brands, it has grown to 29 signatory brands and retailers backed by partner organisations in the value chain, such as suppliers of textiles, leather or chemicals.
At least 127 retailers and brands, along with more than 1,300 suppliers and manufacturers and more than 20 producers, are on board the Better Cotton Initiative which trains cotton farmers on sustainable agriculture practices and for companies to use "better cotton".
A number of international brands such as H&M have rolled out efforts engaging consumers, such as launching eco-friendly clothes ranges - which use sustainably made or recycled materials - and setting up collection points for consumers' unwanted garments to send for reuse or recycling.
Yet the pace of change may not be fast enough, based on an annual assessment of businesses' sustainability and governance strategy by the Global Fashion Agenda and Sustainable Apparel Coalition, along with the Boston Consulting Group.
The Pulse of the Fashion Industry 2019 Update concluded that fashion companies "are not implementing sustainable solutions fast enough to counterbalance the negative environmental and social impacts of the rapidly growing fashion industry".
WHAT IS IN THE WAY?
Challenges abound, from the production chain to the clothes' "end of life".
Ms Circe Henestrosa, head of the School of Fashion at Lasalle College of the Arts, said: "Retailers outsource most of their manufacturing to factories that they don't own. So sustainable processes in the production chain are difficult to track."
Some non-governmental groups have been pushing for fashion companies to take greater ownership and responsibility for the manufacturing process through tracking and asking for greater transparency.
One such group, Fashion Revolution, publishes a transparency index of the biggest fashion brands, with 200 in this year's update.
There is also the issue of dealing with unwanted garments. Reusing or repurposing them is easier than recycling, which is not as efficient a process.
Republic Polytechnic's Mr Kong pointed out that textile recycling consumes energy and requires separating items by fabric type and colour type. Clothes made up of blended fabrics - for instance, a mixed percentage of cotton and polyester - also make separation hard, he said.
"Scientifically, there are existing enzymatic and hydrothermal methods that can be employed to separate most of the blended fabrics. However, the problem is that there is no one standard fabric blend. Every fashion brand carries its own type of fabric blend."
Financial costs play a part too.
Ms Semun Ho, chief executive officer of the local Textile and Fashion Federation, said that a manufacturer which adopts greener practices or a company which pays a premium for sustainably-acquired products can incur higher production costs.
"The costs can be passed to the consumer, leading to increased product prices or if they are absorbed by the company, it would come at the expense of a lower margin," she added.
Supply is one side of the equation.
But on the demand side, consumers who say they care about the environment may not vote with their wallets.
A survey in March this year of close to 3,000 consumers in Brazil, China, France, the United States and Britain by the Boston Consulting Group showed the gap.
While 75 per cent of those surveyed viewed sustainability as "extremely or very important" in fashion, only 7 per cent treated it as a key purchasing criterion.
Asked about local consumers, Associate Professor Sharon Ng, who teaches marketing at Nanyang Technological University's Nanyang Business School, said: "Singapore consumers are more pragmatic. Though they do care about being environmentally friendly, other considerations such as price and features of the products may override sustainability considerations."
A mindset shift about consumption may be needed from the onset.
Fashion Revolution's country coordinator for Singapore, Ms Laura Francois, said: "Buy only what you really need. Search for a second-hand version first. If you can't find it, buy it new and opt for companies that are committed to ethical practices and produce sustainably.