Water EQ2

Question 1

Define drought

Answer 1

Droughts are an extended period of time when there is below average rainfall

Question 2

3 types of drought?

Answer 2

• Meteorological
• Hydrological
• Agricultural

Question 3

Explain meteorlogical droughts

Answer 3

Meteorological drought occurs when there is rainfall deficit

It is caused by changes in atmospheric circulation leading to:

• A lack of precipitation as a result of short-term changes or longer-term trends
• The lack of rainfall is often combined with high temperatures which increases evaporation

Question 4

What is agricultural drought?

Answer 4

Agricultural drought is when there is a water deficiency in the soil, which leads to:

• Crop failure
• Reduced biomass

Question 5

What is hydrological drought?

Answer 5

Hydrological drought occurs when there is a lack of water stored on the surface and underground in lakes, rivers, reservoirs and aquifers

Question 6

What is ENSO?

Answer 6

The ENSO cycle is the movement of a warm water mass in the equatorial Pacific Ocean

It occurs due to the changes in the trade winds, atmospheric circulation and ocean currents

There are two phases:

• El Niño
• La Niña

Question 7

What is the impact of ENSO on the hydrological cycle as a whole?

Answer 7

ENSO disrupts global weather patterns, causing shifts in precipitation and evaporation.

• El Niño brings droughts to some areas (e.g. Australia, Indonesia) and flooding to others (e.g. western South America).
• La Niña often causes the opposite — flooding in Australia and dry conditions in South America.
• Affects evaporation rates, river flows, groundwater recharge, and overall water availability worldwide.

Question 8

What causes El Nino?

Answer 8

An El Niño occurs when the sea temperatures are 0.5°C above average

Question 9

What is El Nino?

Answer 9

Trade winds reverse from E - W to Austrilia (W) to Peru (E). This pushes warm surface water towards SA.

This leads to the creation of warmer average weather in the East Pacific - usually in December every 2-7 years.

Question 10

What are the impacts of El Nino?

Answer 10

The temperature of the ocean off the coast of Peru rises an average of 4-5°C, causing thermal expansion and sea level rise

Water off the coast of Australia and Indonesia is cooler and precipitation is reduced leading to droughts in Australia

Question 11

Explain how El Nino forms?

Answer 11

In a non - El Nino year, there is trade winds travelling from the East (South America) to the West (Australia, Indonesia). This pushes warm surface water to the West and results in warm air rising, causing thunderstorms and floods.

However, El Nino occurs when the trade winds are reduced or reversed. This means there is now warm surface water pushed East to SA. This means in Aus there is upwelling of cold water and dry sinking air causing droughts.

Basically whichever side DOESNT have the warm surface air = cold deep water = dry sinking air = droughts. The side that does have the air = warm water = warm rising air = thunderstorms and floods + thermal expansion and temp increases.

Question 12

What is La Nina?

Answer 12

• La Niña occurs when sea temperatures fall below average
• This brings cooler and drier than average weather in the eastern Pacific
• La Niña occurs every 3-5 years

It is essentially the enhancement of normal trade winds (instead of reversal like El Nino)

Question 13

What causes La Nina?

Answer 13

• Stronger than usual eastward trade winds and ocean currents
• These bring cold water to the surface through upwelling

Question 14

Impacts of La Nina?

Answer 14

• Australia/Indonesia: Gets even wetter than normal, with a higher chance of storms and flooding.
• South America (Peru, Ecuador): Experiences cooler temperatures, leading to drier conditions and more drought.
• Increased rainfall in Australia and Southeast Asia
• Drought conditions in the south of the US
• Increases the risk of tropical storms in the Atlantic

Question 15

What out of the 2 ENSO cycles has the biggest impact?

Answer 15

El Niño has the most significant impacts with:

• Increased rainfall and flooding in South America, Africa and the south of the US
• Drought in Australia and Southeast Asia
• Has been linked to a higher risk of colder winters in the UK

Question 16

How do humans increase the risk of drought?

Answer 16

Over abstraction of surface and ground water aquifers.

Also deforestation - increased risk of drought because it reduces the ability of soil to retain water.

Question 17

Why does over abstraction occur?

Answer 17

Over-abstraction occurs due to:

• Population growth - this increases the demand for both food and water
• Overcultivation

Question 18

Define flooding

Answer 18

Flooding is the result of surplus water within the hydrological system

Question 19

How do intense storms lead to flooding?

Answer 19

Precipitation rate > Infriltration rate = high surface runoff = flash flooding (short lag time)

Common in mountainious and semi - arid areas.

Question 20

How does humidity affect evaporation?

Answer 20

High humiditity = Lots of moisture in air = evaporation BUT it means evaporation slows down / cant climb any more because the air cant hold much more water.

Question 21

How does prolonged rainfall lead to flooding?

Answer 21

Over saturate the soil = soil at its capacity = water cannot infriltrate the soil = increased surface runoff.

Best example are Monsoons - 75% of India’s yearly rainfall is from monsoons.

Question 22

How does rapid snowmelt cause flooding?

Answer 22

If snowmelt is quicker than the rate of infriltration from water than surface runoff increases.

Question 23

What are some other good causes of flooding?

Answer 23

• Soil type - clay = low infriltration - sandy = high.
• Rock type - permeability.
• Urban areas with impervious surfaces.
• Tectonic activity results in dam failure or landslides which block river flows.

Question 24

Define impervious

Answer 24

Not allowing fluid to pass through.

Question 25

In general, what are the 2 ways humans exacerbate the flood risk?

Answer 25

* Changing land use in the drainage basin * Mismanagement of the river using hard engineering

Question 26

How does ploughing farming deforestation etc increase chance of flooding?

Answer 26

Removes vegetation = soil structure breaks down = soil becomes more compact (especialy under heavy machinery and animals) = less porous = surface crusting = blocks water from soaking in = more surface runoff.

Question 27

How does mismanagement of a river channel increase flood risk?

Answer 27

Hard engineered intervention is designed to 'push back' against nature but sometimes it excaebarates or causes worse floods.

Question 28

What is Channelisation?

Answer 28

Adds a liner to a straightened river channel (usually concrete) to reduce friction and improve flow rate, therefore reducing silting.

Question 29

What is silting?

Answer 29

Silting refers to the process where fine particles of soil, like silt and clay, accumulate in water bodies like rivers, lakes, and reservoirs, leading to a build-up of sediment.

Question 30

How can Channelisation cause flooding?

Answer 30

The method displaces the river flow downstream (increased silting or flooding) overwhelming locations during peak discharge. Basically the increased flowrate overwhelms the non - channeled parts of the river leading to silting there.

Question 31

What is river straightenining?

Answer 31

River straightening increases the flow of water by increasing the gradient of a river's channel and removing natural meanders (bends)

Question 32

How can river straightening cause flooding?

Answer 32

Increasing flow velocity, increases risks of flooding downstream if blockages occur or narrowing of the channel through an urban area

Question 33

What are floodplains and how can mismangement of them cause flooding?

Answer 33

**Floodplains are natural natural stores of flood water and self-regulating defences** * Building on these increase the risks of flooding and damage to homes and livelihoods

Question 34

What are some enviromental costs of flooding?

Answer 34

* Loss of crops * Loss of habitats * Pollution of waterways * Soil and bank erosion * **Eutrophication** (excess nutrients lead to oxygen depletion, and ecosystem collapse in water bodies) * Siltation

Question 35

What are some enviromental benefits of flooding?

Answer 35

* Recharge groundwater stores * Recharge of wetlands leading to plant growth * Increase the connectivity between aquatic habitats * Move sediment and nutrients around the landscape

Question 36

What are the socio economic costs of flooding?

Answer 36

* Loss of life, property and infrastructure * Road closure and loss of communications * Long-term rehoming of people * Cost of house insurance increases * Loss of income from employment, agriculture and/or tourism * Health risks from water contamination * Trauma and loss of possessions * Psychological impacts can be long lasting

Question 37

What are the impacts of climate change on precipitation?

Answer 37

Warmer air = holds more moisture = more capacity = more evaporation = more precipitation frequency and intensity. | Areas most affected would be the tropics and high latitudes

Question 38

Impact of climate change on evapotranspiration?

Answer 38

Less plants from deforestation = less transpiration OR Plants respond to heat by opening stomata = higher water loss

Question 39

Impact of climate change on floods and droughts?

Answer 39

More of them.