Water - it's all around us. It's inside our cells, coursing through our veins, and sustaining life for organisms everywhere. It's underground, on the surface, and in the air. But while water may seem unending in supply, the statistics suggest otherwise. Only 2.5% of all water on Earth is fresh water, and only 0.01% of all water is freshwater that is easily attainable by humans from rivers, lakes, and shallow groundwater. Many nations are experiencing severe shortages in water in the modern world and a third of the global population lives in areas with moderate to high levels of water stress. In fact, water scarcity is often cited as one of the top problems facing humankind in this century and may likely be the single greatest source of international conflict over the next 50 years as nations vie for control of shared waterways. At the same time, many rivers and lakes are suffering from eutrophication, sewage pollution, and contamination with harmful chemicals.

If we are to support the billions of people currently alive and those in the future, we must drastically change our outlook on water. We must use less, improve the efficiency of the water we use, and reduce pollution loads to waterways. This module will examine water use in your home and enable you to investigate ways to lessen your overall water usage. It will also familiarize you with the processes used to clean water before and after use.