14 6A.4 Global goals and personal responsibility
- The United Nations Sustainable Development Goals include SDG 6 (clean water and sanitation), SDG 14 (life below water), SDG 13 (climate action) and SDG 12 (responsible consumption).
- Water footprint: the volume of fresh water used to produce goods. Typical values: 1 kg of wheat ≈ 1500 L; 1 kg of beef ≈ 15 000 L; a cotton T-shirt ≈ 2700 L. Reducing waste of food and choosing efficient products saves water.
✍️ Worked examples
Worked example 11.
- Problem. A family of five uses 150 L per person per day.
- They fix leaking taps (which wasted 10 L per day), install water-saving shower heads (saving 20 L per person per day), and stop washing the car with a hose (saving 100 L per week).
- What is the new daily use of the family and the percentage saving?
Solution. Original = 5 × 150 = 750 L/day. Savings: leaks 10 + showers 5 × 20 = 100 + car 100/7 = 14.3 → total = 124.3 L/day. New use = 750 − 124.3 = 625.7 L/day; saving = 124.3/750 = 16.6 %. If a whole city of 1 million people saved the same 16.6 %, it would save about 25 million litres (25 000 m³) per day.