By averaging the instantaneous flow in time, we can get the average flow in a certain period of time, such as daily average flow, monthly average flow and annual average flow. The total amount of water passing through a certain period of time is called total runoff, such as daily runoff, monthly runoff and annual runoff. In cubic meters, ten thousand cubic meters or one hundred million cubic meters.
River classification
It is impossible for a country with a vast territory and many rivers to observe all the rivers in a short time, but the economic development urgently needs data such as river water level, flow change and water temperature dynamics.
Therefore, it is necessary to use river classification to solve the problems raised in production practice. In a certain area, the climate, soil, geology and geomorphology conditions that affect the characteristics of rivers are roughly the same, so there is a certain degree of similarity between rivers.
In different areas, the conditions affecting the characteristics of rivers are very different, and the changing laws of river hydrological factors are of course different. Therefore, according to the existing river hydrological data, rivers with similar element changes can be classified into one category.