دورة المياه

Water Cycle

The water cycle, also known as the hydrologic cycle or the hydrocycle, is a continuous process by which water circulates through Earth's atmosphere via evaporation into vapor, precipitation back down to the earth's surface with rainfall, and the movement of water from higher elevations back towards lower ones due to gravity. This cycle maintains a relatively stable temperature on Earth by distributing heat from tropical regions to polar regions through ocean currents and wind patterns. Understanding the water cycle is crucial for understanding climate change, weather forecasting, and the availability of freshwater resources.

Evaporation

Evaporation is the process by which liquid water changes state into water vapor or steam due to increased kinetic energy resulting from rising temperatures. This happens when sun heats the surface of oceans, lakes, rivers, and wet ground. Water molecules gain enough energy to break free from the surface and form clouds. Evaporation rates are influenced by several factors such as air temperature and humidity, surface area, and wind speed.

Precipitation

Precipitation occurs when water droplets in the atmosphere reach a size that makes them fall back down to the earth's surface in various forms like rain, snow, hail, sleet, etc. It can occur when warm air rises, cools, and condenses around dust particles, creating cloud droplets. When these droplets grow large enough, they become too heavy and fall down as precipitation. The type of precipitation depends on the temperature at the level where this occurs. For example, if the temperature is below freezing point, the precipitation will be frozen water droplets, known as snow or ice pellets.

Collection

Once precipitation falls back down to the earth's surface, it collects in bodies of water such as oceans, seas, lakes, rivers, and underground aquifers. This collection phase involves runoff, where precipitation flows towards lower elevations and fills up reservoirs like lakes and dams. Over time, evaporation and transpiration decrease the volume of this collected water until more precipitation occurs.

Runoff & Infiltration

Runoff refers to the movement of water over land surfaces under the force of gravity. It occurs when precipitation flows across impervious surfaces due to gravity and gathers in streams and drainage channels. In contrast, infiltration is the process by which water seeps into soil pores, cracks, and other openings. Soil acts as a filter, absorbing water and releasing it slowly back into the environment. This slow release helps maintain streamflow during dry periods.

Transpiration

Transpiration is the release of water vapor from plant leaves into the atmosphere. It's essentially the reverse process of photosynthesis - instead of taking water in, plants give out water vapor. Transpiration contributes significantly to atmospheric moisture, helping create clouds, which eventually lead to precipitation.

In summary, the water cycle plays a vital role in regulating our planet's climate, redistributing heat, providing us with freshwater resources, and supporting life on Earth. By understanding this complex process, we can appreciate its importance and make informed decisions to conserve and protect our precious water resources.