While students may acknowledge the impact that land use and development have on our environment, they do not necessarily understand the relationship between human activities and ecosystem responses. Therefore, the nature of the relationships leaves the science teacher to most often present information in a purely narrative form without any hands-on or experimental experience. In this article, the authors introduce a free, simple, and realistic computer simulation program, SimRiver, which allows students to develop a river basin and identify how human activity affects producers, specifically diatoms. This allows students to develop a skill set for understanding nonlinear problems where relationships are not simply cause and effect.