Streamflow, the amount of water flowing in a creek, stream, or river at a certain point in time, is critical to people and the environment. Knowing the amount of flowing water is important for numerous water resources, ecological, and engineering applications including flood forecasting, ecosystem health, environmental flows assessment, infrastructure design, and water supply management used for drinking water, electricity production, manufacturing, and irrigation. In this lesson, students will learn how to measure and calculate streamflow in the field using the velocity-area method.