Edexcel IGCSE Geography Chapter 1 - Pearson Schools

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The inputs of a drainage basin are:●●energy from the Sunprecipitation formed from moisture picked up outside the basin● possibly water from tributary drainage basins – this is not shown in Figure 1.3;an explanation is given below.Most of the flows and stores are broadly the same as in the hydrological cycle.The outputs are:●●the river’s dischargethe water in its basin from which evaporation and transpiration take place andwhich eventually falls as precipitation in another drainage basin.Chapter 1: River environmentsWhy is the hydrological cycle a closedsystem and the drainage basin cycle anopen system?For more on systems, see:• Chapter 2.6 (page 54)• Chapter 5.2 (page 116)• Chapter 5.5 (page 123)sourceABconfluencetributarymouthABKeydrainage basinswatershedlowlanduplandFigure 1.4: Basic features of the drainage basinAs Figure 1.4 shows, it is possible to draw a dividing line between neighbouringdrainage basins. It follows the tops of the hills and is called the watershed. Themain river has its source in the higher parts of the basin close to the watershed.This is where most precipitation falls. Smaller streams or tributaries enter themain river channel at locations known as confluences. The mouth or estuary ofthe river is where it flows out into the sea.Drainage basins can be of at least three broad types. Not all of them simply collectand deliver water directly to the sea. Some of them are just parts of much largerdrainage basins. For example, the basin of the River Negro in Brazil is a tributary orpart of the huge drainage basin of the River Amazon. The water it collects isconveyed to the Amazon and then eventually to the sea. Some drainage basins donot lead, either directly or indirectly, to the open sea. Rather they lead to ‘inland’seas or lakes such as the Caspian Sea, the Aral Sea or Lake Victoria in Kenya.The drainage network is the system of surface and underground channels thatcollect and transport the precipitation falling on the drainage basin. Figure 1.44
shows the channel networks of two drainage basins, A and B. Basin A’s network isless dense (has fewer channels) than B’s, though the main channel is shorter.Channel networks can be mapped and their lengths and densities (number ofchannels per unit area) measured. The network can change over short periods oftime. For example, during flooding drainage basins often have many more andlonger channels than they do in periods of low or normal rainfall.Each drainage basin is unique in its combination of a range of features. Thesefeatures include size, shape, rock type, relief and land use. The features becomefactors that determine how quickly or slowly water moves through the basin.rapid run off–steep slopes;impermeable rockurban area–speedsup rate of runofflittle run off–permeable rock;rivers havedisappearedundergroundwoodland–slowsrate of run offAre you sure you know the differencebetween permeable and impermeablerocks?Chapter 1: River environmentsKeygritlimestoneclayFigure 1.5: Factors affecting run offFigure 1.5 shows how some of these features can affect overland flow or run off.Rock type and relief are physical factors over which people have little control.However, land use can be easily changed by people. Woodland can hold water andslow overland flow. However, once it is cleared for cultivation, run off will speed up.The built-up areas of towns and cities can speed up run off even more. Rainwaterhits solid surfaces such as roofs, pavements and roads. It is then quickly channelledinto drains which speed its delivery into a stream or river.1.3 Hydrographs and river regimesIt can be important to know how quickly any rain falling in a drainage basin orcatchment area will reach the drainage network. It is also important to know howmuch a river’s channel can hold. If the rainwater reaches the river quickly, thechannel may not be able to cope and flooding will occur. The amount of watercarried by a river at any one time is known as its discharge. This is measured incumecs − that is, in cubic metres of water per second moving past a particularpoint along the river’s course.5
Page 1 and 2: Section A:The natural environment a
Page 3: ●●●●overland flow - most of
Page 7 and 8: There are a number of factors affec
Page 9 and 10: ErosionThere are several different
Page 11 and 12: KeyDifference inheight betweenX and
Page 13 and 14: As lateral erosion continues, the b
Page 15 and 16: The height of the drainage basin an
Page 17 and 18: ●●●The rising standard of liv
Page 19 and 20: uses less water (now 14%) (Figure 1
Page 21 and 22: 1.7 Water qualityIn Part 1.6, we lo
Page 23 and 24: Agriculture●●●Liquid from far
Page 25 and 26: There is a fourth and relatively ne
Page 27 and 28: FACTORPhysicalWeatherRockSoilRelief
Page 29 and 30: In the longer term, there is the co
Page 31 and 32: the monsoon climate with its heavy

Edexcel IGCSE Geography Chapter 1 - Pearson Schools

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