Water Cycle and Freshwater sources

• The water cycle is examined, covering its processes and how rainwater returns to rivers or seas.

Water Sources

• Freshwater is naturally occurring, not salty, and safe to drink if cleaned or processed.
• Freshwater comes from rivers, lakes, groundwater, glaciers, and rainwater.
• Total Global water consists of 96.5% oceans, 2.5% freshwater and 0.9% other saline water
• Freshwater is composed of Glaciers and ice caps (68.7%), groundwater (30.1%), and surface/other freshwater (1.2%)
• Surface water and other freshwater is made up of ground ice and permafrost (69.0%), Lakes (20.9%), Atmosphere (3.0%), Soil moisture (3.8%), Rivers (0.49%), and Living things (0.26%).

Freshwater Sources in China

• China has many freshwater sources, including rivers, lakes, and groundwater.
• There are 45,203 rivers, including the Yangtze River, the longest in China and third-longest globally.
• Other major rivers are the Yellow River, Pearl River, Songhua River, Huai River, Hai River, and Liao River.
• There are many lakes, including the five largest freshwater lakes: Poyang Lake, Dongting Lake, Taihu Lake, Hongze Lake, and Chao Lake.
• Lake Poyang is the largest freshwater lake in China.
• Groundwater is the main water source in central and north China

Water Cycle

• The water cycle, also known as the hydrological cycle, involves water flow in different states.
• Water flows between the atmosphere and the lithosphere, which includes the ground surface and underground areas.

Importance of the Water Cycle

• It turns salty water into fresh water that is safe for consumption.
• The water cycle feeds bodies of water on the ground surface with fresh water.
• It maintains the lives of different plant and animal species, including humans.
• The water cycle irrigates crops to provide food and maintains daily life.

Processes of the Water Cycle

• Evaporation occurs when water, in its various forms, absorbs heat energy from the sun.
• Water turns into vapour (gaseous state) and rises into the atmosphere.
• Salt, being a heavy compound, does not evaporate with the water.
• Transpiration happens when water vapour in plants is released into the atmosphere after photosynthesis.
• Evapotranspiration is when water in the lithosphere turns into water vapour and rises up to the atmosphere through transpiration and evaporation.
• Condensation is when water vapour cools, condenses into larger droplets and forms clouds.
• Precipitation occurs when water droplets become too heavy for the air to hold and fall back to Earth as snow, rain, sleet, or hail.

Rainwater Question

• The reason rainwater is not salty is that salt is too heavy to evaporate.
• Since salt does not evaporate, it is not carried into the atmosphere with the water vapour.
• The water vapour then condenses into fresh, non-salty droplets.
• Because plants release water vapour into the atmosphere, it is called transpiration.
• The continuous movement of water within the Earth and the atmosphere is called the Water Cycle

Ways Rainwater Returns to Sea or River

• Infiltration is when water on the ground surface soaks vertically downward into the soil layer.
• This process forms soil storage.
• Percolation is when soil water flows vertically downwards through permeable rock layers with pores.
• This continues until it reaches the water table, forming groundwater and an aquifer above impermeable rock layers.
• Surface runoff occurs when water flows on the ground surface back to the rivers or seas.
• Throughflow is when water soaks into the soil and flows horizontally along the soil layer back to the rivers.
• Groundwater flow is when groundwater stays deep in the rock layers and flows slowly and horizontally back to the rivers.
• The cycle is complete once water is carried from the river into the seas, and then starts again.