Down by the River

River is like stream of water that flows along a channel from the highlands to the lowlands. The great majority of rivers eventually discharge into either the sea or a lake, although some rivers disappear due to water loss through seepage into the ground and evaporation into the air.

Rivers exist as part of the circulation of water through the global environment in the water cycle (or hydrological cycle). Measured by the amount of water in each component of the cycle, rivers represent a very small part of the system. The vast majority of water is saline (salty), with the oceans holding 96.5 per cent of all the water on Earth. Of the remaining 3.5 per cent that is fresh water, most is held in long-term storage either in cold regions as polar ice sheets, glaciers, and snow (69 per cent) or beneath the Earth抯 surface as groundwater (30 per cent). Lakes account for a further 0.35 per cent, while the atmosphere contains 0.04 per cent. Rivers account for a tiny 0.006 per cent of all the fresh water on Earth, and yet they have an importance that dwarfs their volumetric size.





[ Last edited by PeNinGLaLaT on 22-6-2004 at 06:40 PM ]

amorist

Are we going to be discussing runoff, meandering, delta formation, valley formation, etc...etc? :bgrin:

Originally posted by amorist at 22-6-2004 07:13 PM:
Are we going to be discussing runoff, meandering, delta formation, valley formation, etc...etc? :bgrin:

pressure...pressure.......:hmm:

Water in rivers flows under gravity, giving it the power to mould the

landscape through erosion, transport, and deposition of rocks and

sediments, and making it a dynamic and renewable natural resource for

human, plant, and animal life. The water cycle begins when water

evaporates from the oceans into the atmosphere. Atmospheric water

returns to Earth as precipitation in the form of rain, hail, or snow. The

amount of water reaching the ground depends on many factors but, in

general, highlands receive more precipitation than lowlands, and it is in the

mountains that most rivers originate. When precipitation reaches the ground

it usually seeps (infiltrates) into the soil, either percolating down to the

water-table to become groundwater, or flowing slowly downhill as through-

flow. However, during heavy storms, where human activities have

compacted the soil surface or covered it with concrete, or where the soil is

already saturated, not all the water is able to infiltrate and the excess

collects on the surface before flowing downhill to the nearest stream as

overland flow. Water that reaches the river either by through-flow or

overland flow is termed run-off. The role of the river in the water cycle is to

complete the cycle by collecting run-off from the surrounding area (drainage

basin) and carrying it back to the ocean or a lake in order to replace water

that has evaporated.

In Malaysia, rivers have played an important role in the economic, social, cultural and religious life of the people. They have provided a means of transport, helped to established ports and towns, opened up the hinterland, provided a livelihood to the riverine people, brought new settlers inland, irrigated the land, generated hydropower, influenced the culture and traditions of the people for example the ibans in Sarawak, and served as focal points for religious ceremonies such as Thaipusam for the hindus.

Rivers also act as the people's playmate by providing rereational opportunities in various forms as well as posing challenges to the intrepid traveller and the adventure-seeker.

Indeed, the rivers of Malaysia have contributed tremendously in shaping the modern and thriving nation that we call Malaysia today. In essence, the rivers of Malaysia combine the forests, the terrain and the peoples themselves to produce stunning riverscapes, luxuriant riparian forests, and a myriad of cultures that are closely interlinked with rivers.


       

alphawolf

Not only in Malaysia, but in nearly all the countries in the world, cities and civilisations have fluorished by the riverbanks. Some examples:

Kuala Lumpur - Sg. Kelang
London - River Thames
Paris - Seine

Civilisations
Egypt - Nile
Babylon - Rivers of Babylon (Boney M?) - Tigris and Euphrates
Mohenjodaro - Indus
Angkor - Mekong

The Flow

The amount of water flowing along the river (discharge) varies through time and space. Time (temporal) and space (spatial) variations together define the river抯 flow regime. Variation with time occurs because during and immediately following a storm, or after snow-melt in spring, run-off generated by overland flow causes the discharge to increase. Because of the speed with which it reaches the channel, this component of run-off is termed the quick flow. In extreme cases a flood may occur when water arrives so quickly that the capacity of the channel to carry water is overwhelmed and the river bursts its banks to cover the surrounding flat land (flood plain). Water moving below the ground as through-flow and groundwater takes much longer to reach the river, arriving days, weeks, and even months after the precipitation that generated the run-off. This water maintains a low discharge in the river, called the base flow, between rainfall and snow-melt events. However, if no precipitation occurs at all, or if the rate is below average for an unusually long period, a drought results, with the river eventually drying up when lack of ground and soil water recharge by precipitation reduces base flow to zero. This can have disastrous consequences for wildlife living in and along the river, and for people relying on the river for their water supply.


Spatial variation occurs because, as the river flows downstream, its discharge increases, as it collects water from more and more of its own drainage basin, and adds water from the basins of other rivers that join it as tributary streams. Consequently, a river is usually small in the mountains close to its source and much larger in the lowlands close to its mouth. Exceptions occur in deserts, where the rate of water loss due to seepage out of the channel into the parched ground and evaporation loss into the dry atmosphere exceeds the rate of supply from upstream. For example, the Nile is the world抯 longest river, yet its discharge decreases dramatically as it flows from the mountains of Sudan and Ethiopia through the Nubian and Sahara Deserts to the Mediterranean Sea.

SEDIMENTATION

The flow of water in rivers is easy to see, but it is not always appreciated that river flow is actually made up of both water and sediment. The sediment load carried by a river is of great importance because it is the capability of running water to erode, transport, and deposit sediment that is responsible for the dominant role of rivers in forming the world抯 landscapes. Every year rivers carry about 20 billion tonnes of sediment to the oceans. This is enough to lower the land surface of the continents by 3 cm (1ƒ in) every 1,000 years: a rate that dwarfs the action of other agents of erosion, such as wind or ice.

In forming the landscape most rivers display three characteristic regions: close to the source in the headwaters river action is predominantly erosional; in the middle reach the river transports sediment eroded from upstream; and in the lower course it deposits sediment to build new land. For a discussion of these regions and the landform features that characterize them.

Lakes / Rivers in Malaysia  

Batu Dam  
Batu Hampar  
Bentong Hot Springs  
Chamang Waterfalls  
Durian Tunggal Recreation...  
Empang Jaleh  
Hutan Lipur Bukit Kubu...  
Hutan Lipur Bukit Lagong...  
Jeram Besu Rapids  
Jeram Lenang  
Jeram Pasu  
Kampung Bebuloh (Water Vi...  
Kampung Hulu Kenas Waterf...  
Kampung Kuantan Fireflies...  
Kampung Patau-Patau (Wate...  
Kenyir Lake  
Krian District  
Lakeside Recreation Centr...  
Lata Beringin  
Lata Iskandar  
Lata Jarum Waterfalls...  
Lata Kekabu  
Lata Kinjang  
Lata Sungai Bil  
Paya Indah Wetlands Sanct...  
Puncak Janing  
Sekayu Waterfall  
Seri Perigi  
Sungai Berkelah  
Sungai Kenau  
Sungai Sedim  
Sungai Sendat Waterfall...  
Taiping Lake Garden  
Taman Tasik Perdana (Lake...  
Tanjung Kala  
Tasik Bera  
Tasik Chini  
Tasik Melati  
Tasik Pedu  
Tasik Raban  
Tasik Temenggor  
Tasik Timah-Tasoh  
Teluk Gong Wetlands  
Teluk Intan Boatyard  
Tow Foo Sportsfishing Cen...  

Erosion


Erosion is the means by which a river deepens, widens, and lengthens its channel. There are several main erosional processes.

Hydraulic action occurs because the energy of the flowing water hitting the boundaries of the river channel, especially the banks, is sufficient to prise away fragments of the bedrock. This hydraulic shearing force is caused by the fact that water is forced into cracks in the bedrock. The air in the cracks is compressed and, as a result, pressure increases. Over time this weakens the rock and fragments break away. An extreme form of hydraulic action, associated with waterfalls and rapids, is cavitation. It is caused by air bubbles collapsing. The resulting shock waves hit and weaken the channel boundaries, and may eventually cause the banks to collapse. Hydraulic action is measured in terms of shear force per unit area, which is termed the boundary shear stress. As well as eroding fragments of intact bedrock, the river may also erode loose particles梫ariously termed scree, talus, or colluvium梩hat have accumulated at the base of slopes after being detached from the bedrock by weathering processes such as freeze-thaw, the growth of salt crystals, or the actions of plants and animals. This process is termed sediment entrainment.

The efficacy of flowing water in erosion is greatly assisted by the battering effect against the bedrock of the channel of sediment already in motion, a process called corrasion. Corrasion is responsible for much of the downcutting that creates and deepens the channel, and is most effective in times of flood. A particular form, potholing, occurs when pebbles or other sediment are trapped in hollows in the bed and are swirled around by turbulent eddies, scouring out and deepening the depression. It is not only the channel that is worn away by this process; the sediment load is itself abraded by collisions between individual particles and between particles and the channel boundaries. This process, sometimes called attrition, reduces the size of transported particles with distance downstream and also gives them the rounded shapes typical of river cobbles and pebbles. Finally, water is also a strong solvent. Many rocks can be eroded by being dissolved by water, a process known as corrosion, or solution. Limestone and chalk are particularly susceptible to corrosion, but many chemical compounds are soluble, particularly in their weathered state, so a wide range of rocks may be vulnerable.





[ Last edited by PeNinGLaLaT on 1-7-2004 at 09:38 PM ]

Long Rivers

The longest river in the world is the Nile.  Egypt's greatest river is 4,160 miles long! In fact, Africa has two of the ten longest rivers.

The second longest river is the Amazon, of course! It is about 4,000 miles from start to finish, winding its way through most of South America.

China lays claim to Numbers 3 and 4: The Yangtze River is 3,964 miles long, and the Huang He is 3,395.

How do we measure these rivers? Geographers calculate the distance from the source of the river to its mouth. For instance, the Ob-Irtysh River, which is Number 5 on the list, is 3,362 miles long from its source in southern Russia to its mouth in the Ob Bay, in the very cold waters off northern Russia.

Russia has two more rivers in the Top Ten. Number 6 is the Amur River, which flows through Siberia and is 2,744 miles long. The Lena River, at Number 7, flows north through central Russia and is 2,734 miles long. The Congo, which flows through central Africa, is Number 8 at 2,718 miles long.


North America's longest river is also Number 9: the Mackenzie, in Canada, at 2,635 miles. Rounding out the Top Ten is the Mekong River, in Southeast Asia, at about 2,600 miles long.

You can see a big difference from Number 1 to Number 10. The Nile is 2,000 miles longer than the Mekong.  

Tak fahamlah saya bahas inggeris ni. Boleh kah sesiapa terjemah ke dalam bahasa melayu?