Water cycle

                               This is a summary of the water cycle.

Hydrological / Water cycle

• Describes the continuous movement of water on, above and below the surface of the Earth.
• Although the balance of water on Earth remains constant over time, individual water molecules can come and go, in and out of the atmosphere.
• This is an open system.

Importance of the Water Cycle

• Imagine if there was no water cycle - water would evaporate but then none would form clouds, none would fall as precipitation, none would fill up the lake/streams, eventually it would all evaporate and we would run out of water
• It is how water reaches plants, animals, and human beings
• It moves nutrients and sediment in the different aquatic ecosystems
• Linked to climate as it involves atmosphere, oceans and land
• It is how the earth's water recycles itself

 

 

 

Processes

Precipitation:

Condensed water vapour that falls to the Earth's surface . Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet.

    

Runoff:

The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

 

Infiltration:

The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.

 

Subsurface flow:

The flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface, as a spring or by being pumped, or eventually seep into the oceans. Groundwater tends to move slowly, and is replenished slowly.

 

Evaporation:

The transformation of water from liquid to gas phase. The source of energy for evaporation is primarily solar radiation.

 

Sublimation:

The state change directly from snow or ice to water vapour.

 

Advection:

The movement of water — in solid, liquid, or vapour states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.

 

Condensation:

The transformation of water vapour to liquid water droplets in the air, creating clouds and fog.

 

Transpiration:

The release of water vapour from plants and soil into the air. Water vapour is a gas that cannot be seen.

 

Percolation:

Water flows horizontally through the soil and rocks under the influence of gravity

As the Earth develops, human activities start to take place, and it affects the nature processes.

Human activities that affects the water cycle include:

• agriculture
• industry
• alteration of the chemical composition of the atmosphere
• construction of dams
• deforestation and afforestation
• removal of groundwater from wells
• water abstraction from rivers
• urbanization

Effects on climate
86% of the evaporation occurs from the oceans, reducing the temperature by evaporative cooling. Without the cooling, the effect of evaporation on the greenhouse effect would lead to a much higher surface temperature and a warmer planet.


Name: Soh Jing Wen
Class: 7 Kappa
Date: 6 July 2013