There Is Time Between Rainfall and a River's Response

Rain today does not imply that a river will change in the same way today. Where the rain fell, what happened in the soil, which path the water followed, and how long that path took all contribute to the river's response. Delay is part of the relationship.

Suppose little rain falls near a river gauge while much more falls upstream. Looking only at the local sky will not explain what the river does next. Near the river mouth, other hydrological influences may matter too. Placing two numbers on the same graph does not automatically establish causality.

Time-series analysis should test which rainfall period aligns with which later river response. Even a strong alignment does not prove a single cause. Other changes and model limitations still need consideration.

Environmental systems interest me because their outcomes are distributed through both space and time. A point measurement can be useful, but without a map of the pathway it rarely tells the whole story.

Source: official reference.