RIVER ENVIRONMENTS TEST NOTES Edexcel IGCSE Geography Section 1: Physical environments.

The hydrological cycle

Global circ water CLOSED SYSTEM. Fixed amount water. None enters/exits Earth + atmos.

Hydrological cycle stores

Atmos - Water vap/ minute droplets clouds.

Land + Surface water: vegetation, bedrock, water bodies

Sea - 95% water in sea. Liquid but also ice + icebergs.

Amount water can't change, proportion diff stores can, eg sun's energy, melting ice sheets

Hydrological cycle flows

Evaporation - Water converted liquid to gas

Transpiration - Take up liquid water from soil + 'breathe' it into atmos as water vapour.

Evapotranspiration - Loss moisture ground by direct evaporate from water, soil + transpiration.

Condensation - Change atmos - water vap cools + liquid. Liquid becomes water droplets appear in atmos as clouds.

Precipitation - Transfer water in any form from atmosphere to land/sea surface.

Overland flow - Most precipitation hits ground moves due to gravity then enters stream, river, lake. (run off)

Infiltration + percolation - transfer water downwards through soil + rock + into aquifer/groundwater store.

Throughflow - As result gravity, water moves slowly through soil until reaches stream/river.

Groundwater flow - groundwater transfer water to rivers, lakes + sea.

Drainage basins and their features.

-Drainage basin OPEN SYST. External inputs + outputs.

-Amount water varies over time. In HC, remains same.

Inputs and outputs of drainage basin

Inputs drainage basin:

-Energy sun.
-Precipit from moisture picked up outside basin.
-Water from tributary drainage basins.

Outputs drainage basin:

-Rivers discharge
-Water in basin from evaporation + transpiration.
-Then falls precipitation other drainage basin.

Watershed

Dividing line 2 drainage basins.

-River has source higher parts basin close to watershed where most precipitation falls.

-Streams/tributaries, enter river confluences.

Drainage basins at least 3 broad types

-Those collect + deliver water directly into sea

-Those parts larger DB. River Negro.

-Ones do not lead, directly/indirectly, into open sea. Lead to 'inland' seas/lakes like Caspian Sea.

River regimes and hydrographs
Features of river regimes

-Rain reaches channel quickly, flooding. Amount water 1 point DISCHARGE. Measured CUMECS.

River discharges:

-Variations = RIVER REGIME. Reflects climate

-Feature hydrographs - jaggedness.

Storm hydrographs

-Storm hydrograph change discharge after storm. Rain hit ground, time reach river + rise.

Delay peak rainfall + time is causes river to rise = LAG TIME

Short lag time, water reaches river channel quick + rises. Short lag time, more chance flood.

Storm hydrograph shows discharge 2 flows:

Base flow - 'normal' discharge of river

Storm flow - additional discharge after rainstorm.

Factors affecting river regimes.

-Amount + intensity rain. Heavy rain not sink ground. Overland flow/run off, reach river.

-Temp. Below freezing, snow, no melt. Ground frozen, melting snow surface reach river quickly.

-Steep slopes - rapid surface run off. Flat + gently sloping land - water sinks into soil.

-Rock type - impermeable no rain sinks - speed run off. Permeable infiltration + percolation

-Veg + land use - trees + plants intercept + delay rain reaching ground. Tarmac speeds run off.

-Human intervention. - dams + reserv intervene river regimes. Hold discharge, control water.

Weathering and mass movement

-Rivers shape landforms.

-EROSION, TRANSPORT + DEPOSTITION.

-Partner weathering + mass movement

-Involves elements weather, esp rainfall + temp

Physical weathering

Breaks down rocks smaller pieces. Changes temperature + rain freezing + thawing rock cracks.

Chemical weathering

Rocks decay + disintegrate. Acidic rain, pourous rocks.

Biological weathering

Roots plants, grow cracks in rocks, break apart.

Mass movement

-Rocks broken down, down slope under gravity.

-MASS MOVEMENT river valleys, 2 types.

-Slumping, bottom valley side cut by river. Unstable + material slumps to river. Helped heavy rain, lubricant.

-Soil creep - material slowly down slope under gravity. Collects bottom valley side + eroded river.

Fluvial processes

Erosion - HYDRAULIC ACTION

-Water hits river bed + banks, material dislodged

-With heavy rain/high discharge.

ABRASION

-Mats carried river rubbed against sides + floor.

-'sandpaper' action widens + deepens.

CORROSION (solution)

-Minerals rocks at sides channel dissolved by water

Transport

-Movement mats LOAD by river.

-Contains materials eroded river from sides channel.

TRACTION

Large boulders rolled along bed

SALTATION

Small boulders bounced along bed

SUSPENSION

Lighter material carried along by river flow

SOLUTION

Material dissolved in water

Deposition

-DEPOSTITION - drop mats river when decrease energy, speed + discharge.

Wetter climate - more discharge, more erosion + transport. Softer rocks easily eroded + transported.

Downstream changes in river characteristics

Long profile - source to sea etc. Smooth, concave.

Steep + irregular flowing above sea level in uplands.

-Irregularities when outcrops hard rock across valley. *Natural lakes + reservoirs disrupt smoothness

Much gentler + smoother runs through lowland country + reaches destination.

River channel starts narrow + shallow (v shaped) with rough edges. Becomes wider, deeper + smoother.

-Discharge, velocity + load transported increase downstream. Size sediment load finer + rounded.

Upland landforms

Main river landforms in upland areas are:

-Steep V-shaped valleys , interlocking spurs, waterfalls + gorges.

-Been formed mainly by process river erosion. weathering + mass movement also played part.

Upland long profile

-In uplands, long profile steep + river flows fast.

-River cuts downwards. Hydraulic action + abrasion erode river bed + make valley deeper. Steepness + deepness valley = mass movement material down sides.

-Some material river load + helps abrasion. Valley floor narrow + often completely occupied by river.

Interlocking spurs

-Interlocking spurs where river swings side to side.

-Main work river cutting vertically downwards into bed.

-River cuts down to flow between spurs higher land on alternate sides valley.

Waterfalls

-Waterfalls where band hard rock more resistant to erosion than softer rock below it.

Softer rock easily eroded water as falls over hard cap rock. Falling water, plunge pool at bottom.

Overhang of hard rock collapses as soft rock below is eroded. Waterfall retreats leaving gorge. Gorge not widened as capping hard rock

Lowland landforms

-Channel + valley wider, deeper + smoother, river velocity + discharge increase, despite gentle gradient.

-River course plan (map) view less straight.

Valley cross-section

-Valley cross-section wider + flatter.

-Floor occupied flood plain. End course, flood plain spreads out, delta/estuary*.

Lowland landforms erosion

Lowland, still eroding. *Less vertical as close sea level.

More lateral erosion - wears away sides, especially outside meanders. Agent of deposition.

As river loses energy, drops some load flood plain. Usually mud, stones + organic matter.

Every time river leaves channel, velocity decreases. Sediment deposited across valley floor.

Great thickness sediment builds up. Most deposition banks channel, higher than rest flood plain, levees.

Meanders and ox-bow lakes

1) Force water undercuts bank outside bend forming steep bank to channel, called river cliff/bluff.

2) Underwater current w spiral flow carries eroded mats to inside bend where flow water slower.

3) Deposited, form bank,slip-off slope/point bar.

4) Bend meander becomes more pronounced.

5) Times flood, river's energy much greater, narrow neck meander breached, flows straight again.

6) Redundant keeps some water, ox-bow lake.

Delta

Delta final landform. Vast areas alluvium at mouths.

Eg. Ganges Brahmaputra, 1.7 billion tonnes sediment/y.

Load dropped as deposit faster tides remove it sea.

*Creates new land.

Case study: The river tay (UK) and its valley

UPLANDS

River Tay fed streams draining slopes Grampian Mountains. Precipitation upland parts DB high (well over 1000mm a year) + slopes steep.

Height DB + steep slopes = large amounts run off. Curving river - interlocking spurs.

Valley cross-section V-shaped + steep sided. River fills valley floor. Cross-section = river still flowin above sea level. River erosion vertical rather than lateral.

Case study: The river tay (UK) and its valley

LOWLANDS

Flat + low lying land; valley cross-section = flood plain 600 m wide where River Earn meets River Tay.

Shows typical estuary features at mouths rivers:

-Wide channel - up to 2km
-Sand + mud banks
-Some areas marsh
-Channels of deeper water

Water uses, demand and supply
Water facts

3 per cent water freshwater; rest salt water in seas. 75% freshwater glaciers/ice sheets, *20% groundwater.

-Essential to life
-Vital to economic development
-*Unevenly distributed - 'water rich' + 'water poor'.

Fresh water needed for

-Domestic use - bathing; toilet; drinking etc

-Industrial use - producing goods from beer to steel

-Agricultural use - irrigate crops; water for livestock.

-Leisure use - sport fishing rivers; sailing on lakes etc

Demand and supply

-Demand - Water consumed = level demand.

-Supply - meet demand water w various sources

Water balance

For any country/area within it, can compare water demand and water supply. WATER BALANCE

DEMAND

Water demand X3 last 50y - Growth world pop. Rise demand + consump water also as aspects dev:

-Rising standard living - more domestic use water.

-Rise agri prod needed as growing pop

-Industrialisation key part dev. Facto big cons water

Water short supply + taken from wells, women take water from well - hard work, over long distances.

Link between development and water consumption

-2 'worlds of water'.

-Consump dev countries high. 1200 cubic metres/p/y

-Consump developing, 400 cubic metres/p/y

Developed + Developing countries use of water.

Diff use water. Dev countries - mainly agriculture.

-Developed, ind then agr. Domestic 3x more dev

SUPPLY

-Rivers + lakes - Source used earliest humans

-Reserv, artificial lakes, building dam across valley + allowing flood. Stored + collected behind dam.

-Aquifers + wells - In porous rocks (aquifers). Groundwater obtained drill wells/boreholes to aquifer.

Water surplus and deficit

3 types area:

-Water deficit areas - demand over supply

-water-surplus, supply exceeds demand.

-water-neutral areas, water balance equal.

'Two worlds of water'

Water surplus remote, mountainous, high rainfall, few people + low water demand.

Water deficit - Africa, Middle East, Australia + parts North + South America. Little annual precipit.

Others deficit as big pop + rising dev.

Ways of moving water from surplus to deficit areas

-By hand, bottles + buckets, motor vehicles, tanker ships.

-Most widely used, long-distance pipelines + canals.

Water quality and supply

Importance of water quality

Qual key domest uses: drink, cook+ washing.

-Needed to grow crops + rear livestock. Polluted water threatens human health + diseases - Cholera

How location affects water quality

Water qual poor dry climates w marked dry season.

-Dry season, stagnant + diseases + pollution. Levels pollution v high urban areas, dev nations + ind areas.

Sources of water pollution - agriculture

-Liquid farm silage + slurry farm animals enters rivers.

-Fertilisers + pesticides seep into groundwater.

-Deforestation - run off carries soil + silt to rivers. Serious effects aquatic life + humans drinking water.

Sources of water pollution - industry

Industry:

-Cooling water for electric power station river + returning it at higher temp upsets river ecosystems.

-Spillages from ind plants, oil refineries enters rivers.

-Working metallic minerals + use water processing ore, toxic substances find way into rivers.

Sources of water pollution - domestic

Domestic:

-Discharge untreated sewage from houses

-River washing clothes + bathing contaminates water.

-Emptying highly chlorinated water swimming pools

Access to safe water

Safe water fit for human consump - not contaminated. Over 1B, no access. Suffer ill health + early death.

Most dev countries, 90% pop access clean water.

Lowest access safe water: Africa + southern Asia.

Managing supply of clean water - COLLECTION

Collection, from key sources, rivers, reservoirs etc

Managing supply of clean water - TREATMENT

-Must use treated water, untreated, highly polluted.

-Removes pollutants, pure for human consump.

-Substances removed, suspended solids, bacteri etc

Chlorination - removes biological growth.

Aeration - removes dissolved iron + manganese.

Sedimentation - removes suspended solids.

Filtration - removes very fine sediments.

Disinfection - kills bacteria.

Managing supply of clean water - DELIVERY

-Often delivered treatment works to consump by pipes.

-Cost install + maintain high. Not maintained, wastage.

-Urban dev nations, via standpipes streets.

-Villages, wells, - untreated. Buckets dirty/polluted

-Plastic bottles filled source. V costly + inefficient.

CASE STUDY

River management lessons from Spain

-Mediterranean climate - Spain's annual rainfall small.

-Most falls winter half, summer droughts common.

-Availability + demand water Spain do not coincide.

-Basic idea projects - transfer water sparsely pop centre Spain for water south-east, esp for irrigation

PROJECT 1: TAGUS SEGURA PROJECT

-286km-long series aqueducts + canals to carry water 2 reserv upper Tagus valley to big reserv Segura valley.

-Distrib from reserv to cons Alicante, Murcia + Almeria.

Problems due to project:

-Irrigation water to agribus rather than local farmers.

-Consumed by urban dev + resorts along coast

-Availability water = wasteful/extravagant use.

PROJECT 2: THE EBRO PROJECT

-2001, plan to dam + divert longest river, Ebro. Building 100s dams upper Ebro + 100s kilometres canals.

-Would transfer 100 billion litres water/y same arid south-eastern parts Spain as water from Tagus.

Project abandoned 2004 due to:

-Bad experiences Tagus-Segura project

-Threat posed Ebro delta, agri area + wildlife wetland.

CONSEQUENCES OF BOTH PROJECTS

-Meet growing shortages via desalinisation plants.

CASE STUDY

River management lessons from China

PROJECT 1: The three gorges project

-Start 1997, generate elec + control flooding. Longest HE generators dam, 10% China's demand elec.

-Demand rises w dev + grow pop. Env + global warming, key China not burn coal. Better water transport.

-BUT 1M lost homes + resettled. Cities, towns + villages drowned. Flooded most fertile land.

-Silt trapped, farmland less fertile, water qual low, waste behind dam. Must cope frequent earthquakes*

PROJECT 2: The south-north water transport project

-Econ + pop growth, North China Plain, Beijing + Tianjin.

-Huge demand water, 200M pop, heavy ind+ irrigation

SNWTP est, demand greater than availability.

-Moving water 'surplus' south, 'deficit' north. Transfer 12T gallons water/y over 1000km on 3 diff routes.

-Eastern + central routes 2013 + 2014, linked existing canals, rivers + lakes. Work Western dam stopped as:

-Awareness of 'costs' outweighing benefits.
-Levelling off demand, pop + econ growth slowed.

Costs and benefits of SNWTP

COSTS:

-South, water shortages, exporting water North.
-Many displaced for transfer routes.
-Wildlife + ecosystems disturbed as transfer routes.
-Loss water as evap from open canals used.
-V expensive project + burden on taxpayers

BENEFITS:

-North powerhouse Chinese economy.
-Much-needed water to important industries.
-More irrigation water for food prod.
-Health risks reduced as access safe water.
-Showcase Chinese engineering + technology.

CONSEQUENCES OF BOTH PROJECTS

Reconsidering ways uses + manages rivers by:

-Lower water lost evap as bad irrig + open canals.
-More recycling by modern treatment methods.
-Tightening controls poll. More easily re-used.
-Recharging groundwater stocks lowered by overuse
-Price up. Discourage people + bus using wastefully.

SUMMARY OF SPANISH AND CHINESE CASE STUDIES

China + Spain, same lessons water supply + river manag:

-Transfer schemes appear most effective to shortage water, but big financial, social + env costs.

-Move away ambitious transfer proj, different ways. Spain, desalinisation, China searching transfer schemes.

CASE STUDY

Plans to manage the Blue Nile, Ethiopia

-Shortage water + energy why Ethopia dev difficulty.

-Will be met in basin Upper Blue Nile.

-Trib meet, big river before lowlands + in Sudan.

-Lake Tana-Sudan border, 850km, fall 1300m.

-Work started Grand Renaissance Dam 2011

-Due to finish 2017, only 73% completed 2020.

-6000MW elec + irrig water. Funded Ethiopian gov.

-Sudan + Egypt felt 'steal' too much Nile's water.

-Now recognised benefits these 2 nations.

-New era Ethiopia's dev.

Flooding - causes and control

CAUSES - Physical factors

Physical factors:

-Weather - Run off quick w prolonged heavy rainfall. Exceeds infiltration capacity + ground saturated.

-Sudden rise temp above freezing, rapid snow melt.

-Rock - Impermeable rocks limit percolation + encourage rapid surface run off/overland flow.

-Soil - Slow infilt capacity some soils speeds run off.

-Relief - Steep slopes cause rapid run off.

-Drainage density - If high - many tributary streams carry rainwater quickly to main river.

-Vegetation - Low density veget absorbs little water + does not seriously slow run off.

CAUSES - Human factors

Human factors:

-Deforestation - Low interception + speed run off.

-Urbanisation - Tarmac = quick delivery rain main river.

-Agriculture - Risk flooding up if soil bare, overgraze, monoculture + ploughing down not across

-Burning fossil fuels - Raising global temp, melting ice sheets + glaciers = more rainfall + frequent storms.

CONCEQUENCES - Effects on environment

-Landslides

-Soil contamination by sewage

-Vegetation destroyed

-Destruction of settlements

-Loss of wildlife habitats

-Soil erosion

CONSEQUENCES - Effects on people

-Loss of belongings

-Damage to property

-Disruption to transport

-Disease + stress

-Insurance claims

-Contaminate water + loss services e.g. gas

-Crops + animals lost

-Death + injury

IMMIDIATE AND LONG TERM EFFECTS OF A FLOOD

IMMEDIATE:

-Loss life
-Destruction property + crops
-Homelessness
-Disruption of transport + communications
-Loss water supply + sewage disposal

LONG TERM:

-Cost replacing everything lost + damaged
-Cost removing silt as flood waters go down

CONTROL

Flood control + flood management:

Construction - Block + dispose. Costly. Hard eng:

-Dams
-Levees
-Sluice gates

Adjustment - Soft engineering, work w nature:

-Restoring river natural state
-Preserve marshes + wetlands
-Strict planning controls minimise building flood plain.
-Encouraged have flood ins.
-Flood warning systems + what to do in emergency

Prediction:

-Prediction (extent + depth) key. Helps gov prepare.
-Helps stop build houses, facto etc high risk flooding.
-BUT floods vary. Must assess which level flood should give protection (risk assessment.)