Certified Storm Water Operator Practice Exam

A hydrograph is specifically designed to illustrate the change in water flow rate over time, especially during and after storm events. It allows for the analysis of how precipitation events influence streamflow, showcasing how quickly runoff enters the river system and how long it takes for flow rates to peak and subsequently recede.

In contrast, while the annual rainfall amount is an important aspect of hydrology, a hydrograph more accurately focuses on flow rates rather than cumulative precipitation over an entire year. Temperature variations in bodies of water are measured separately and do not correlate with the purpose of a hydrograph, which centers on flow dynamics. Similarly, the types of vegetation surrounding water bodies do not reflect flow rates or changes over time, making them unrelated to the function of a hydrograph. Thus, the depiction of water flow changes over time during storm events is the essence of what a hydrograph represents, reinforcing why this is the correct answer.