How did scientists commonly measure the rate of water flow in a river?

The measurement of water flow rate in a river is commonly carried out by determining the time it takes to fill a container of a known volume. This method provides a straightforward calculation of flow rate based on the volume of water passing a specific point over a given timeframe.

By utilizing a container that has a set capacity, scientists can accurately gauge how quickly water moves past a certain location in the river. The rate of flow can then be calculated using the formula:

Flow Rate (m³/s) = Volume (m³) / Time (s).

This approach is practical and offers precise data about water movement, vital for various scientific analyses concerning ecology, hydrology, and environmental management.

Other methods mentioned, such as measuring water temperature or observing fish movement, do not directly quantify the flow rate in the same systematic way, and counting ripples lacks the accuracy needed for a reliable measurement of water flow. These alternatives could provide indirect information about river conditions but wouldn't effectively yield a specific flow rate.