WATER CYCLE

Terrestrial part of the water cycle

• Runoff: Precipitated water flowing to the soil surface without seepage or evaporation. Important phenomenon on bare soils.
• Infiltration: Movement, under the effect of gravity, of the water through the superficial layers of the ground and flow of this water in the soil and the subsoil. The infiltrated water can also join the groundwater. In this case, the term percolation is used.
• Groundwater: Water stored in the soil and supplying the sources.
• Storage in depressions: Water trapped in hollows and depressions during and after a shower. Eventually, this water will evaporate, infiltrate the soil or be used by vegetation.
• Interception: The portion of precipitation retained and captured by vegetation or buildings that will never reach the surface of the soil. This water will eventually evaporate. This phenomenon is a loss at the hydrological level.

The Watershed will react differently to the precipitation it receives depending on, among other things, the shape, size, slopes, soil type and density of the hydrological network. Another aspect of particular importance is the use of soil in the watershed. Different activities rub shoulders in the watershed: residential, agricultural, forestry, industrial, etc. These activities have an impact on water dynamics in the watershed. Thus, vegetation cover greatly influences the erosion that can occur since there is a direct link with precipitation interception and soil stabilization.

In an urban environment

Impermeable surfaces prevent infiltration into the soil, increasing runoff and the rate of response of the watershed. This results in a rapid rise in the level of watercourses.

In an AGRICULTURAL setting

The vegetation cover may vary. When soils are protected by vegetation, the impact of raindrops is less. However, when soils are exposed, runoff can be significant and cause erosion. The arrangement of plants also plays a role. For example, runoff will be greater in a corn field where the plants are aligned than in a grassland where the layout is random.

In the FORESTRY environment

The vegetation cover will intercept some of the precipitation thus limiting runoff and consequently erosion.

*Text taken from Our lakes beneath the surface.