Definition:

The water circulation system is a key material circulation system of the earth that connects the atmosphere, hydrosphere, lithosphere and biosphere through the phase change and spatial migration of water. Its internal driving force comes from the three-phase conversion ability of water, and its external power depends on the solar radiation and the gravitational effect of the earth.

The water cycle can be categorized into three levels based on spatial scale: the global water cycle, the watershed/regional water cycle, and the water-soil-vegetation system. The global water cycle is a closed system, while the watershed water cycle is open. Ecological restoration projects enhance system resilience by optimizing infiltration and runoff processes. This system directly impacts the distribution of 0.014% of the world’s surface freshwater resources, and its stability is crucial for preventing and controlling droughts and floods.

The internal mechanism

The core driving force of the water cycle system stems from the physical phase change properties of water. Liquid water evaporates to form gaseous water vapor, which condenses into solid ice crystals or liquid precipitation upon cooling, completing the three-phase transformation. Solar radiation provides the heat necessary for evaporation, while Earth’s gravity governs the descent of precipitation and runoff. Together, these forces create an energy gradient that drives the continuous migration of water molecules.

Taxonomic hierarchies

The global water cycle, through processes such as evaporation, water vapor transport, and precipitation, forms a closed loop, maintaining the global balance of 137 billion cubic meters of water. The watershed water cycle, an open system, includes 12 stages of runoff formation, such as interception, storage, and infiltration. The water balance in this system follows the principle that ‘precipitation is approximately equal to runoff plus evapotranspiration.’ The water-soil-vegetation system focuses on scales from millimeters to meters, where vegetation interception reduces surface runoff, and root infiltration enhances soil water retention.

Ecological applications

In the field of ecological restoration, removing hard riverbanks and restoring ecological buffer zones can enhance a river’s self-purification capacity by 40%. Constructing terraced ponds can achieve 75% local infiltration of rainfall, forming a’ soil sponge’ with an annual regulation capacity of millions of cubic meters. Restoring floodplain wetlands can increase flood storage capacity by 3 to 5 times. By 2025, studies have confirmed that such measures can improve the resilience of cities to urban flooding.

Maintenance management

Specific maintenance specifications should be followed in industrial applications, such as the anti-freezing treatment requirements of the supporting system of the laser cutting machine: when the ambient temperature is lower than 0℃, the water stored in the pipeline should be emptied in time after shutdown.

Industry data for 2013 showed that equipment failures due to non-compliance with the standard accounted for 23% of total damage.