Rivers have been integral to human lives since ancient times. They provide us with freshwater and food, and facilitate agriculture, hydroelectric power and navigation. River basins were the cradles of early human settlements and communities - where human civilization began.

 



Sources of Food and Drinking Water

Some 97% of the earth's surface water contains salt so cannot be drunk directly; a further 2% is stored as ice at the poles. Only 0.1% of freshwater can be easily collected and utilized. This water is mainly in rivers, streams and inland lakes. Freshwater fisheries also profoundly impact our livelihoods and economies.




Irrigation

Irrigation for agriculture - mainly from rivers and streams - makes up 71% of freshwater use worldwide. Further, river sediments carry large amounts of organic matter, and concentrate downstream to form fertile flood plains that are the most suitable places for farming. Major agricultural developments originated here.




Hydroelectric Power

Globally, about 25% of electricity comes from hydroelectric power, and fulfils 5% of energy demands. Most hydroelectric power stations are built along large rivers. The Three Gorges Dam (Sanxia) on the Yangzi River (Changjiang) is the world's largest dam. From 2011, this is set to generate 100 billion units (kWh) of electricity each year.


Hydroelectric power station


Navigation

Many large rivers, such as the Nile of Eygpt, the Mississippi River of America, the River Po of Italy and China's Pearl River, are major navigation routes. Yet rivers in Hong Kong are too shallow for such purposes; only few can accommodate inland river transport, which has already been completely phased out.






The Nile of Eygpt© Dorothy Lai


Ecological Functions

Habitats along rivers and streams are home to countless animals and plants. Aquatic plants including mosses and liverworts, algae, ferns and flowering plants form the base of the food chain, as they produce their own food by photosynthesis. These plants are food for herbivores and shelter for a host of these and other species. They absorb inorganic nutrients such as nitrogen and phosphorous and balance the composition of nutrients in the water. They can also stabilise silt and stones, so helping reduce erosion.

 

Abundant fish, amphibians, reptiles, crustaceans, shells and insects are nurtured by rivers and streams. Different species have different demand for habitats. Therefore, a diversified ecological environment in the rivers and streams is very important for the population growth of different living organisms.

 
Acorus tatarinowii
Predaceous Chub (Parazacco spilurus) is a freshwater fish that's vulnerable to extinction in China. It is, however, common in Hong Kong.
© Ken Ching
Green Cascade Frog (Odorrana livida) lives in fast flowing hill streams.
Mountain Water Snake (Sinonatrix percarinata) is a great swimmer and frequent visitor to rivers and catchwaters.


Many Odonates are indicators of the health of riverine ecosystems.
Common Kingfisher (Alcedo atthis)
© Patrick Wong

Mosses and liverworts are common plants in rivers and streams.




Chinese Barb (Puntius semifasciolatus)  are often found in local freshwater streams.

 

Small Long-armed Shrimp (Macrobrachium hainense) often hides between rock crevices

 

Leisure

Rivers are ideal places for leisure, outings and sports such as fishing and rowing, which in turn may result in substantial tourism and economic benefits. Venice in Italy and China's Yangzi River are world famous tourism hotspots. Niagara Falls and the Grand Canyon along the Colorado River are among the world’s seven major natural landscapes. Hong Kong has some rivers and streams that are charming, and rich in plants and animals as well as other geographical resources that can help research and education.

 

 





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