We all know that our bodies need water. Water cleans our body, controls our temperature, and helps to keep us 1. About 70% of our body is water.We often read that we have to drink at least eight glasses of water a day (about two litres). The idea probably came from mineral water companies! 2, how much water we need depends on the weather and on what we’re doing. When we are hot, or if we do sports or exercise, we need to drink more. Some experts say that, 3 normal conditions, we only really need about one litre a day. When temperatures are very low we also need to drink 4 than on a normal day. This is because we wear a lot of clothes so we sweat a lot and 5 water.