Independent: Water In short supply in many parts of the world, water will be come even more scarce as demand grows. Average consumption in the UK, at 146 litres per person a day, is only slightly less than the 152 litres used daily 15 years ago. The heatwaves and water restrictions of recent years have, however, encouraged some, such as 34-year-old Neil McNiven, an electronics engineer from Kidwelly, Carmarthenshire, to do more to save water. "I started collecting rain in various …