In this lesson, students learn the value of clean freshwater and the natural processes that ensure an adequate supply of usable freshwater. In activity 1, students learn about the importance of water quality for human health and agriculture. Students brainstorm the different ways that people use water, from household use to industry and agriculture. Statistics related to the quantity of water on the planet help students understand that water is a finite resource. Students relate their own activities to the water supply to put their own consumption in activities. Students then brainstorm various threats to the water supply. In activity 2, students conduct a hands-on activity that focuses on the role of natural areas as filters that produce clean water. Such natural filters are contrasted with impervious (paved) areas to compare the impact of development on the ability of nature to provide clean freshwater.