Investigating the Precipitation-Streamflow Relationship

Graph illustrating the relationship between precipitation and streamflow.

The intricate relationship between precipitation and streamflow is illustrative of the complexity and changing nature of the water cycle. These key aspects can be investigated to help understand the water cycle. The duration and intensity of the precipitation, soil porosity, the slope of the ground, and the time of year emerge as some of the potential factors in this investigation.

Step-by-step instructions will guide you through the following processes: locating and downloading web-based streamflow and precipitation data, importing the data into a spreadsheet, and generating a graph that displays the day-to-day relationship between these two variables across a full year. The inquiry starts once the graph is complete. The patterns that emerge from the graph are sometimes predictable and sometimes quite puzzling. As you consider questions about this complex relationship and search for answers, you will develop a deeper understanding of some of the basic dynamics of the water cycle. There is no attempt in this chapter to quantify the precipitation - streamflow relationship.

Although the particular case study in this chapter is valuable for introducing the procedures related to a precipitation–streamflow investigation, you will have greater opportunities for inquiry if a local watershed is available for study. In a local investigation, you may have the opportunity to visit the watershed to gather information about factors such as slope, soil composition, and vegetation. You'll also have the opportunity to request information from local officials or environmental agencies.