Water Cycle

Question 1

Human causes of drought?

Point 1

Answer 1

Drought is when an area experiences a water shortage. One human cause of drought is due to overgrazing. Overgrazing accelerates the onset of drought. Overgrazing causes agricultural drought as less water is made available for soils, reducing plant growth and biomass as there is no time for plants to recover. Means there is less groundwater storage and transpiration by plants. This reduced transpiration stops rainfall cycles. This occured in the Sahel where rural populations doubled very 20 to 30 years, meaning more food was needed and this meant overgrazing occured.

Question 2

Human causes of drought?

Point 2

Answer 2

Secondly deforestation causes drought. This is because forests are responsible for interception, reducing infiltration, overland flow and high levels of transpiration. Deforestation reduces this and reduced transpiration means that precipitation levels will fall, which causes a positive feedback loop, whereby less precipitation reduces transpiration further. This has occurred in Amazonia, where 20% of forests has been lost creating a drier climate.

Question 3

Physical factors on storm hydrographs?

Answer 3

PHYSICAL FACTORS (of drainage basin) THAT AFFECT HYDROGRAPHS -

• SHAPE - Circular basins have shorter lag times (flashy river) elongated basins tend to be delayed (flat river)
• WEATHER - intense storm which exceeds infiltration capacity of the soil (flashy river) steady rainfall less than infiltration (flat river)

Question 4

Human factors on storm hydrographs?

Answer 4

HUMAN FACTORS THAT AFFECT HYDROGRAPHS -
URBANISATION - makes surfaces impermeable which restrict percolation and encourage rapid surface runoff (flashy river) permeable rocks allow percolation and so limit surface runoff (flat river)
DEFORESTATION - Deforestation reduces interception (flashy river) afforestation increases interception (flat river)

Question 5

Human factors on drainage basin?

Answer 5

OVER EXTRACTION OF WATER
-Human use of irrigation for extensive cereal farming has led to declining water table levels in areas such as the Texan aquifers. The effects of over extraction can be seen with the Aral Sea between Kazakhstan and Uzbekistan, with the volume of water reducing by 75% from 1960 to 1995.
-This has implication for groundwater
URBANISATION -
-Impermeable surfaces increase surface runoff which means drains deliver rainfall more quickly and consequently rivers increase flooding.
DEFORESTATION -
-Deforestation leads to a reduction in evapotranspiration and an increase in surface run-off. This increases flooding potential, leads to a decline of surface storage and a decrease in the lag time between peak rainfall and peak discharge. In other words, it speeds up the cycle. Furthermore, as seen in Nepal this has implications downstream with increases in sediment.

Question 6

Social impacts of flood?

Answer 6

• LOSS OF LIFE - 2017 N.India flood killed 5,700 and injured
• LOSS OF INFRASTRUCTURE -Boscastle 2004, £15 million housing damage
• MIGRATION -National geographic says million are likely to become ‘climate refugees’ and areas such as Maldives are at low-lying risk and has seen Maldives buy land in Australia

Question 7

Impacts on human well-being for the degradation of the water and carbon cycles [20]

WATER CYCLE

Answer 7

Water - WEATHER

• The WC is a closed system but the water moves between the stores proportionally. Global warming means higher temperatures, a warmer atmosphere has a greater water-holding capacity. Thus, combined with higher temperatures means article ice is melting, joining the sea and beginning un-drinkable saltwater.
• Furthermore, higher temperatures leads to thermal expansion of the water volume in the ocean. Estimates from National Geographic say the sea in on average globally 8 inches higher than it was in 1900. This means certain areas such as the Maldives where of its 200 islands the average height above water is just 1.5m are very much at risk from floods as seen in the 1970 storm surge of Bangladesh where over 500,000 people died. This also affects human crop production as seen with the 2013 Typhoon Haiyan in the Phillippines which flooded 71,000 hectares of crop land
• Changing rainfall patterns as climate bands move away from tropical zones. Many areas will experience longer periods of drought, leading to environmental issues such as soil erosion, fires, tropical disease extension and issues for food production. Social and economic deterioration and mass migration will also occur as a result. Other areas will experience increased rainfall, causing flash floods.

Question 8

Impacts on human well-being for the degradation of the water and carbon cycles [20]

CARBON CYCLE

Answer 8

• Oceans are an important carbon sink but their role in doing so is increasingly changing their overall pH and acidifying them. Up until the early 19th century the average oceanic ph was 8.2 but this has already to 8.1 in 2015. Oceans are always likely to be first affected due to their “cold” corals and Furthermore, in the past few decades average Arctic temperatures have risen twice as fast as global averages. As a net sink, Arctic stores far more carbon than any other region and thus the impacts of climate change are amplified. Essentially, if this acidification continues this will lead to the breakdown of coral which will have negative implication to the whole ecosystem and those who rely upon coral such as fish. This in turn, will then affect human well-being in many ways. Firstly, economically many countries depend on exports of fish, in particular China who’s fish trade is worth over $7 billion annually. Secondly, this will affect tourism with countries such as the Maldives where 220,000 are reliant upon their coral attolls to attract 1 million visitors each year. This also has social implication as coral protect people, it’s estimated coral reefs protect 200 million people globally from waves in low-lying areas such as Hawaii and Bangladesh. Furthermore, this also affects humans as for many coastal regions fish and aqualife is their source of food such as Vietnam where over 5m of the population is influenced by the sector, over 10%
• Increased ch4 released from destabilisation of wetlands and sea floor deposits containing methane as well as from thawing permafrost

Question 9

Physical causes of drought?

el nino

Answer 9

EL NINO

• El Nino events occur every 3 to 7 years and usually last for 7 years
• During El Nino cool water normally found along the edge of Peru is replaced by warm water which can lead to drought
• El Nino events seem to trigger very dry conditions throughout the world usually in the second year. For example, the monsoon rains in SE Asia and India often fail
• La Nina events usually but not always follow El Nino they involve the build up of cooler than usual subsurface water in the tropical part of the Pacific, this can cause drought particularly on the western coast of South America

Question 10

Physical causes of drought?

global warming

Answer 10

GLOBAL WARMING

• Warm so greater Water holding capacity
• more evaporation than precipitation

Question 11

drainage basin inputs

Answer 11

Precipitation, what differs is

Form - snow/rain
Amount - will affect amount of water in the drainage basin and fluxes between them
Intensity
Seasonality
Distribution - Important for big rivers like Nile where tributaries are in different climates

Question 12

drainage basin outputs

Answer 12

EVAPORATION
The process by which moisture is lost into the atmosphere from water surfaces, soil and rock
TRANSPIRATION
The biological process by which water is lost from plants through minute pores and transferred to the atmosphere
DISCHARGE
Also known as channel flow into another, larger drainage basin a lake or sea
Distribution - Important for big rivers like Nile where tributaries are in different climates

Question 13

physical factors that affect drainage basins?

Answer 13

CLIMATE
Has a role in influencing the type and amount of precipitation overall and the amount of evaporation such as the major inputs and outputs. Climate also has an impact on the vegetation type
SOILS
Soils determine the amount of infiltration and throughflow and indirectly type of vegetation
GEOLOGY
Impacts on subsurface processes such as percolation and groundwater flow and therefore on aquifers. Indirectly, geology affects soil formation
VEGETATION
The presence of vegetation has a major impact on the amount of interception, infiltration and occurance of overaland flow as well as on transpiration rates

Question 14

explain why the global hydrological cycle is an example of closed system

Answer 14

Firstly, the water cycle has no external inputs or outputs. Essentially, this means that no water is taken out or put into the hydrological cycle at any stage. Thus, this means the water cycle is closed as the amount of water in the hydrological cycle is finite and unchanging.

Secondly, stores and fluxes highlight the water cycle as closed. A store is a reservoir where water is held such as an ocean. A flux is the rate of flow and processes in different stores (oceans, cryosphere, on land and atmosphere). Whilst these stores vary such as climate warming causing sea level rise, thus rising the amount of water in the ocean stores whilst decreasing the amount on land as ice. Therefore, whilst the hydrological size of each store varies this will be proportionally replaced in another store. Therefore, overall the cycle remains closed.

Question 15

what is a river regime?

Answer 15

A river regime can be defined as the annual variation in discharge or flow of a river at a particular point.

Question 16

Explain why river regimes are likely to vary between drainage basins [8 marks]

basin

Answer 16

Firstly, a river regime will vary in accordance to the size of river basin. Large rivers that flow through several distinct regions and receive water from tributaries in a variety of climatic or relief areas, may have a simple regime in their upper reaches and a complex one towards the river mouth as the effect of the different tributaries is felt in the main channel.The River Rhone is an example of this. The annual flow close to the source, near Geneva in Switzerland is different to that of the mouth in Southern France (1,720 m3/s compared to 6,685 m3/s)

Question 17

Explain why river regimes are likely to vary between drainage basins [8 marks]

soil + rock type

Answer 17

Secondly, rock and soil type affects regime with permeable rocks and soils (such as sandy soils) absorbing water easily, so surface run-off is rare. Contrastingly, impermeable rocks and soils (such as clay soils) are more closely packed. Rainwater can’t infiltrate so water reaches the river more quickly. Pervious rocks (like limestone) allow water to pass through joints, and porous rocks (like chalk) have spaces between the rock particles.

Question 18

Explain why river regimes are likely to vary between drainage basins [8 marks]

land use

Answer 18

Finally, land use affects river regime. In urban areas, surfaces like roads are impermeable - water can’t soak into the ground. Instead, it runs into drains and eventually runs into rivers. In rural areas, ploughing up and down (instead of across) hillsides creates channels which allow rainwater to reach rivers faster, increasing discharge. Furthemore, deforestation means less interception, so rain reaches the ground faster and surface run-off will increase.

Question 19

Using named examples, suggest two impacts of drought on ecosystem functioning [6 marks]

Answer 19

Firstly, drought causes water bodies to dry out. Consequently, aquatic animals die. Primary predators such as Heron’s who rely on fish no longer have food. Next, this has implications for other larger predators such as foxes who eat birds. Essentially, this impacts upon humans who rely on animals for food.

Secondly, droughts affect soil where moisture is key for the breakdown of organic matter. As a result, plant life such as trees will die due to lacking nutrients. This means plantlife can no longer absorb carbon from the atmosphere which consequently means the process of global warming occurs more quickly

Question 20

Explain the meteorological causes of river flooding [8 marks]

Answer 20

Firstly, intense storms cause flash flooding, this is when intense precipitation vastly exceeds evaporation and infiltration. As a result, the water levels in the river will exceed the bank and flood the surrounding area. Notably, as seen with the Boscastle flood of 2004 where 3.5 inches of rain fell in 1 hour.

Secondly, rapid snowmelt causes river flooding. Particularly, this occurs during a warm spring, as on the plains of Siberia Bangladesh which is a particularly flood prone country mainly because it is a land of floodplains and deltas built up by rivers such as the Ganges. The river is swollen twice by a year by meltwater from the Himalayas and by the summer monsoon.

Finally, impermeable rocks cause river flooding. If the basin’s soil is impermeable, maybe because it has been saturated by previous rainfall or has been baked by prolonged heating, then any precipitation that falls won’t infiltrate.

Question 21

Explain why there is an increasing global demand for water [8 marks]

Answer 21

Firstly, demand for water has increased due to human factors. Population growth was meant there is more people reliant on our own water supply. For instance, since 1990 the global population has risen from 5.2 billion to 7.2 billion. This means 2 billion more people are now reliant upon water for basic supplies such as cleaning. Secondly, rising living standards in particular the rise of global middle class with the ‘BRICS’ nations means there’s more wealthy people that can afford to spend more and with in either the creation or transportation of virtually every product this strains air water resources.

Secondly, physical impacts have limited our water supply causing greater demand. Due to climate change we have a warmer atmosphere which has a greater water-holding capacity, moving drinkable water into a different store (the atmosphere) and meaning just 2.5% of freshwater is in attainable land stores. Furthermore, rising temperatures melt the sea turning freshwater in to saltwater. Thus, the amount of water available has decreased which has increased demand.

Question 22

ENVIRONMENTAL IMPACTS OF FLOODS

Answer 22

Firstly, river floods have environmental impacts. A river flood occurs when precipitation exceeds transpiration and evaporation. Consequently, the water body in the river will exceed the river banks. This can lead to riverbank erosion whereby sediment can act as a form of water pollution that can dry riverbeds and streams as well as reduce storage capacity for reservirs and methods. Moreover, river floods pollute the surrounding area where the surface run-off effects. As was the case with the 2010 Pakistan floods where 20% of the country’s cropland were inundated and 2.4 million hectares of unharvested crop lost. Furthermore, pollution affected wildlife with 12 species of aquatic wildlife directly affected with 200,00 cattle lost on a wider scale according to a BBC report.

Question 23

ECONOMIC IMPACTS OF FLOODS

Answer 23

Secondly, floods have economic implications as seen with the 2004 Boscastle floods with £108 million of damage. Floods have impacts on the surrounding areas such as destroying infrastructure used for industry and business. As seen in Kerala where property damage cost US$5.6 billion and 980,000 evacuations meant the workforce was largely depleted. Furthemore, floods can impact on other industry as seen with the 2004 Boscastle floods which saw tourism over 5 years hit by 18%. As the population of the area are largely employed in this sector this had negative implications for the economy. Thus, economic impacts are more important than environmental impacts as the problems are felt in multiple areas

Question 24

Evaluate the contribution of large-scale schemes to increase water security [20 marks]

POINTS

Answer 24

HARD = china south - north, mega dams, desalination

SOFT = smart irrigation, NEWater, rainwater harvesting

Question 25

china south - north water transfer

Answer 25

China’s South-North transfer project is non-sustainable. The project aims to transfer 44.8 billion cubic metres annually from south to north. The project is set to cost US$62 billion making it too expensive for developing countries and thus unsustainable on a global scale. Furthermore, the project has displaced 330,000 people, a social disadvantage. Moreover, recent droughts in the south such as 2011 where water levels in the Han River fell so low there was no water for crops let alone to send to the north. Moreover, scientists believe pollution from factories along the eastern route may make the water unfit to drink. Thus, the project is unsustainable.

Question 26

mega dams

Answer 26

Another hard engineering scheme is mega dams. Nearly 60% of the world’s major rivers are impeded by dams such as the Colorado, Nile and Yangtze. Mega dams produce hydroelectric power which is a greener form of energy having far less implications for the water cycle compared to other forms of energy and thus protecting water security. However, this scheme has drawbacks such as the high evaporation losses from the water surface as well as the disruption of the downstream transport of silt.

Three Gorges Dam,
Yangtze River dolphin die
10% of China’s electricity
1.3 million forced to move

Question 27

desalination

Answer 27

Finally, desalination is considered the most sustainable hard-engineering scheme. Given the increasing pressure on freshwater resources and their storage in the drier parts of the world. The process most commonly occurs in Middle Eastern states such as Saudi Arabia, Kuwait and UAE. Purely in terms of addressing water insecurity desalination is the most effective scheme although it does have an ecological impact on marine life. Furthermore, as is the case with the majority of hard-engineering schemes they’re very expensive which makes them unsustainable for less wealthy countries.

Question 28

smart irrigation

Answer 28

Firstly, smart irrigation as used in China and Australia is a method by which traditional sprinkler and surface flow systems are being replaced by modern automated spray technology and advanced drip irrigation systems.

Question 29

rainwater harvesting

Answer 29

Finally, rainwater harvesting is a cheaper alternative to water management. Rainwater harvesting jars such as used in Uganda are 10,000 litre tanks that full during the two rainy periods annually and supply for the future summer periods. Whilst supplies have the potential to be contaminated the scheme is largely sustainable due to the low maintenance costs and no environmental impacts involved.

Question 30

NEWater

Answer 30

Firstly, Singapore’s approach to water management is largely sustainable. Singapore’s approach is known as NEWater and currently supplies 40% of their water needs, rising to 55% by 2060. The water is produced following a 3 part process which turns the recycled water drinkable and has passed over 15,000 scientific safety tests. Whilst this process is largely sustainable there are concerns over the scalability of the project and whether it could support a larger population. Thus, not making it wholly sustainable.

Question 31

Assess the extent to which some approaches to future water supply management are more sustainable than others. [12]

POINTS

Answer 31

Newater

north-south

water harvesting

Question 32

Explain how climate change might have significant impacts on the operation of the water cycle. [8]

precipitation

Answer 32

Firstly, climate change impacts upon precipitation. A warmer atmosphere has a greater water-holding capacity. It is argued that the mode of precipitation may be more important than the amount in determining the impacts. Widespread increases in rainfall intensity are expected more than large increases in total amounts. Areas of precipitation increase include the tropics and high latitudes. The length and frequency of heatwaves is increasing in some locations and is resulting in the increased occurrence of drought. With climate warming, more precipitation in northern regions is falling as rain rather than snow. As the IPCC have indicated, a higher temperature leads to increased evaporation from oceans which leads to increased precipitation in higher latitude hence changing the relationship between the stores.

Question 33

Explain how climate change might have significant impacts on the operation of the water cycle. [8]

evaporation and transpiration

Answer 33

Secondly, climate change is affecting evaporation and transpiration. Evaporation over large areas of Asia and North America appears to be increasing. Transpiration is linked to vegetation change, which in turn affects soil moisture and precipitation. As a result, increased evaporation means water will be held in the atmosphere, causing an inbalance in the water cycle due to the increased flux between the ocean and atmosphere.

Question 34

Explain how climate change might have significant impacts on the operation of the water cycle. [8]

soil moisture

Answer 34

Finally, soil moisture will be affected. Whilst precipitation is increasing so is soil moisture. However, climate change will likely make precipitation irrational and increased. Thus, causing flooding more regularly.

Question 35

normal circulation

Answer 35

‘Teleconnections’ is the overall term for meteorological weather conditions and the connections between one area and another. Normal circulation is when warm, moist area rises, cooling and condensing, forming rain clouds. The warm air rises over the western-side of South America in countries such as Chile. The circulation of wind in a normal year blows from east to west along the equator causing the warm water to be pushed westwards towards South America.

Question 36

el nino

Answer 36

Next, El Nino’s are different in that the air circulation loop is reversed, this leads to disrupted trade winds both over South America and Australia. Cold water normally found along the coast of Peru is replaced by warmer water. At the same time, the area of warmer water further west, near Australia and Indonesia is replace by cooler water. This is the oceanic process altered during an El Nino year with upwelling, which is the rise of deeper colder water to shallower depths. Specifically, the effects of El Nino are felt most strongly in South America. For instance, El Nino’s reduce the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustains abundant sea birds. The reduction in upwelling leads to fish deaths off the shore of Peru. During the 1983 El Nino, Peru was hit heavily with flooding due to some rivers containing over 1,000 times their normal flow. Additionally, El Nino’s have impacts globally. Positively, in Europe El Nino’s reduce the instances of hurricanes. Contrastingly, in the North America region such as Canada, mild winter temperatures are felt. In the southern area of the continent such as the Gulf Coast with Florida more precipitation is felt.

Question 37

la nina

Answer 37

Finally, La Nina episodes may, but not always, follow an El Nino event. They involve the build up of cooler subsurface water in the tropical area of the Pacific. The circulation of air is in the same direction as normal circulation and therefore in an opposite direction to El Nino’s but is simply stronger than normal. This situation can lead to droughts as seen in Argentina, 2018 where economic damages due to crop losses topped $3.4 billion. Globally, La Nina impacts are felt across Europe with milder temperatures. Moreover, stronger winds are felt along the equatorial region, especially in the Pacific. Furthermore, conditions are more favourable for hurricanes in the Caribbean and central America region.