Anything that ends up in lakes end up in streams and end up in our oceans. Then that water evaporates and takes anything that is small enough up into the clouds. When it rains, what comes down is called acid rain. It is extremely corrosive and dangerous to your body. The whole cycle repeats itself, and the only way to stop it is by cleaning our water and keeping it clean.
In most third world countries, people don't have clean water to drink everyday. We all need to appreciate how lucky we are and start thinking about how we use our water.
Without water we would all not exist. So, taking any actions on the treatment of water will benefit everyone, not just yourself. Animals and plants (without water plants wouldn't survive so we wouldn't get oxygen and our air would be toxic) also need water as well. The next time you take a sip of water, think about what you could do to prevent yourself from not getting another.