FRESHWATER Chui Wing Chi(7) Wong Suet Yee(28)

Facts about freshwater: Freshwater lakes, rivers, wetlands and underground hold only 2.5% of the world's water. By comparison, saltwater oceans and seas contain 97.5% of the world's water supply. Over two thirds of the earth's fresh water exists as ice in the form of glaciers and ice caps. Of the total world's freshwater supply, about one third is found underground.

Source of freshwater supply: In the world Lakes Rivers

Glaciers Underground Wetlands

In Hong Kong Reservoirs The Tai Lam Chung Reservoir ( 大欖涌水塘 )The Shek Pik Reservoir ( 石壁水塘 ) Plover Cove Scheme （船灣淡水湖） The High Island Reservoir （萬宜水庫）

DongJiang water

Water cycle:

Importance of freshwater: Agriculture (Most of the water used by human) Heavy industrial processes (e.g. pulp and paper manufacturing, food processing, totally 2/3 of water used.)

Power stations ( cooling water) Domestic use (a small amount of water)

Causes of freshwater contamination or pollution: Hot water from factories discharged into rivers Untreated agricultural and industrial wastes including toxic chemicals are dumped into rivers  pollute drinking water  kill freshwater fish  algal bloom in costal areas runoff from agricultural fields that contain nutrients, sediment, animal wastes, salts and pesticides cause pollution.  the level of oxygen decreases  kill aquatic organisms

Toxins leach into groundwater through soil from petrol storage tanks, landfills, and industrial waste sites  drinking groundwater contains high conc. of heavy metals Toxins seep into the soil at riverside landfills. Underground petrol storage tanks pollute groundwater.

Problems of overuse of groundwater: Water Out > Water In  decrease in groundwater volume Pumping > Groundwater Recharge  decrease in water table Drop in water table  higher cost for pumping (electricity) Produce irreversible ground subsidence in regions built on former lake beds, floodplains and deltas Active and passive saltwater intrusion

Land subsidence Occurs in a small spot  collapse of the land surface (sinkhole) Occurs over large areas (may not notice by people) A sinkhole in Florida, US. This is the agricultural area of California. Years and years of pumping ground water for irrigation has caused the land to drop. The top sign shows where the land surface was back in 1925! Compare that to where the man is standing (about 1977).

Reference: ontamination.html e/SectorsandThemesGroundwater ruselect.htm

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