EQ2- what factors influence the hydrological system over short- and long- term timescales

Question 1

what is a drought?

Answer 1

a shortfall or deficiency of water over an extended period, usually at least a season.

Question 2

what are the physical causes of doubt thought to

be?

Answer 2

down to atmospheric circulation:
the ICZM which varies n and s of the equator seasonally and causes wet and dry seasons
La Niña and El Niño

Question 3

what is sea surface temperature anomalies

Answer 3

relates to how much temperatures of the sea surface, recorded at a particular time, differ from the long-term average. Anomalies may be positive or negative. a positive anomaly occurs when the observed temperature is warmer than the average. A negative anomaly is when the observed temperature is cooler than the average.

Question 4

describe normal air circulation

Answer 4

trade winds push warm water westwards where it evaporates, condenses and forms rain clouds.
area most affected: Australia

Question 5

describe what happens in an El Niño year

Answer 5

disrupted trade winds can cause warm water reversal so the air circulation is reversed. Trade winds typically travel east so water evaporates, condenses and forms rainclouds near regions like South America and thus drought in Australia

Question 6

describe what happens in a La Niña year

Answer 6

very strong air circulations causes very warm water to travel eastwards towards Indonesia where air evaporates, condenses and precipitates.

Question 7

what is meant my desertification

Answer 7

the process by which one-productive land gradually changes into desert-like landscapes. It usually takes place in semi-arid land on the edges of existing deserts. The process is not necessarily irreversible.

Question 8

what is an example of human action making drought worse?

Answer 8

the desertification of the Sahel region of Africs

Question 9

what are the natural causes of desertification

Answer 9

• changing rainfall patterns with rainfall becoming less reliable. occasional drought year sometimes extends to several years
• vegetation cover becomes stressed and begins to die, leaving bare soil
• bare soil is eroded by wind and occasional intense showers
• when rain does fall, it is often only for very short, intense periods. This makes it difficult for the remaining soil to capture and store it.

Question 10

how do humans enhance the impacts of drought?

Answer 10

over-abstraction or surface water from rivers and ponds and of groundwater from aquifers

Question 11

why do humans enhance the impacts of drought?

Answer 11

population growth: pressure on land to grow more food

overgrazing: too many cattle, sheep and goats destroy vegetation cover
overcultivation: intense use of marginal land exhausts the soil and crops will not grow
deforestation: trees are cut down for fuel, fencing and housing. roots no longer bind the soil and erosion ensues.

Question 12

where is drought a recurrent annual feature?

Answer 12

Australia

30% of the country is affected by serious or severe rainfall deficiency

Question 13

why do Australia face these droughts and what is a key event?

Answer 13

the El Niño affect

the ‘Big Dry’ of 2006

Question 14

how are Australia managing their drought issue?

Answer 14

• careful management of scarce water supply
• sorting out competing demands for irrigation and urban dwellers
• large-scale recycling of grey water
• constructing desalinisation plants
• devising new water conservation strategies

Question 15

what is grey water?

Answer 15

waste bath, shower, sink and washing water. It can be recycled but not necessarily for human consumption

Question 16

what is ecological resilience

Answer 16

the capacity to withstand and recover from natural events (such as drought and flooding) or some form of human disturbance.

Question 17

what important functions do wetlands carry out?

Answer 17

• acts as temporary water stores
• giant filters trapping pollutants
• provide a nursery for fish and feeding areas for migrating birds

Question 18

what impact can drought have on wetlands?

Answer 18

less precipitation > less interception (vegetation becomes stressed)
less infiltration and percolation
evaporation will increase
transpiration will decrease

Question 19

how are forests significant in the hydrological cycle?

Answer 19

responsible for interception which in turn means reduced infiltration and overland flow

Question 20

how does drought threaten forests?

Answer 20

drought increases tree mortality which impacts the carbon store

Question 21

what do surpluses in the hydrological cycle more often that not mean

Answer 21

flooding

Question 22

what are the meteorological causes of flooding?

Answer 22

• intense storms which lead to flash flooding, as in semi-arid areas but more in mountainous regions
• prolonged heavy rainfall, such as during the asian monsoon and with the passage of deep depression across the UK
• rapid snowmelt during particularly warm spring, as on the plains of Siberia

Question 23

what is meant by flash flooding?

Answer 23

distinguished by its exceptionally short lag time- often minutes of hours

Question 24

what is an area prone to flooding?

Answer 24

Bangladesh
land is a floodplain only a few metres above sea level.
rivers like the Ganges swell twice a year due to meltwater from the Himalayas and summer monsoons.
Chittagong is especially at risk

Question 25

what is a storm surge?

Answer 25

caused by very low air pressure which raises the height of the high tide sea. strong on-shore winds then drive the raised sea towards the coast.

Question 26

what type of flooding occurs from storm surges?

Answer 26

tidal flooding

Question 27

what physical circumstances will increase the likelihood of flooding?

Answer 27

• lowlying areas with impervious surfaces like towns and cities
• where the grout surface is underlain by impermeable rock
• when ice dams suddenly melt, the water in glacial lakes are released
• jokulhaup (ice meets volcano)
• when earthquakes destroy dams etc

Question 28

describe 3 forms of river management

Answer 28

channelisation: an effective way of improving river discharge and reducing the flood risk. however it simply displaces the risk down stream
dams: block the flow of sediment. Build up of silt in reservoir causing increased river bed erosion
river embankment: designed to protect from floods of a given magnitude. They can fail if the flood exceeds their capacity.

Question 29

what are some socio-economic impacts of flooding

Answer 29

• death and injury
• spread of water-borne diseases
• trauma
• damage of property
• disruption of transport and communication
• interruption of water and energy supply
• destruction of crops and loss of livestock
• disturbance of everyday life and work

Question 30

what are some environmental impacts of flooding?

Answer 30

• recharged groundwater stores
• increased connectivity between aquatic wildlife
• soil replenishment
• for some species, flooding can trigger breeding, migration and dispersal

Question 31

what is meant by eutrophication?

Answer 31

the process of nutrient enrichment that ultimately leads to the reduction of oxygen in rivers, lakes and ponds and the consequent death of fish and other species

Question 32

what are three key years where the UK experiences floods?

Answer 32

2007
2013
2016

Question 33

describe the 2007, 2013, 2016 uk floods?

Answer 33

-same basic cause: heavy prolonged rainfall
during 2016, large areas of the UK received more then twice the average amount of rainfall for that time of year.
cumbria was the most badly hit

Question 34

what were the recriminations regarding the inadequacy of flood protection measures

Answer 34

• budget cuts in money spent on flood defences
• poor land management
• global warming

Question 35

what are the impacts climate change have on the outputs and inputs?

Answer 35

precipitation:
-widespread intensity of intense rainfall is due to increase
-length and frequency of heatwaves is causing drought 10 and 3o degree n of the equator
-in northern regions due to climate change more precipitation will fall as rain rather than snow
Evaporation and Evapotranspiration:
-evaporation over large areas of Asia and N America are increasing
Soil moisture:
-soil moisture will increase where precipitation does

Question 36

what are the impacts climate change has on stores and flows?

Answer 36

• increased runoff and reduced infiltration
• decreasing length of snow cover season
• glacial retreat
• warming of oceans causes more frequent cyclones and rising sea level

Question 37

what are some impacts of SHORT TERM climate change on the water supply?

Answer 37

• loss of snow and glaciers as a store threatens many communities in mountain areas e.g Himalayas
• greater evapotranspiration desiccates the forest store
• increased frequency of droughts due to global warming and oscillation is an issue for rained agriculture