Enquiry 2 What Factors Influecne The Hydrological System Over Short And Long Term Timecales ?

Question 1

Droughts

Answer 1

Long period of time with below average precipitation

Question 2

Meteorological causes of drought

Answer 2

Short term precipitation deficit

ENSO cycles

Anticyclones (Air does not rise so condensation and cloud formation does not occur)

Changes in the ITCZ

Question 3

El Niño

Answer 3

Reverse of walkers cell

High pressure accumulates above Australia, causing drought whilst s America becomes a low pressure centre (at risk of flooding and intense rainfall)

Question 4

La Niña

Answer 4

Intensification of walkers cell

Australia has a low pressure system and s America experience drought due to high pressure

Question 5

Desertification in Sahel

Answer 5

Causes are essentially naturally

Set in motion a downward spiral:

Changing rainfall patterns (less reliable)

Vegetation cover becomes stressed and dies

Bare soil eroded by wind and occasional intense rain

Question 6

Human factors act as a feedback loop for drought

Answer 6

Pop growth- rapid puts pressure on land to grow more food

Overgrazing- too many goats

Over cultivation- intense use of marginal land exhausts the soil and crops will not grow

Deforestation- trees are cut down for fuel- roots not longer bind the soil and erosion ensues

Question 7

Wetlands

Answer 7

50 years ago were considered as wastelands

Act as temporary water stores

Recharge aquifers

Giant filters trapping pollutants

Drought- less precip=,less infiltration and percolation

Water table fall

Evap increase= decrease transpiration = reduce valuable functions

Main challenge to then is artificial drainage

Question 8

Forests

Answer 8

High levels of transpiration

Coniferous forest- susceptibility of pines to fungal diseases

Tree mortality increase (also affect carbon stores)

Tropical rainforests- greater impact on large trees

Ecological resistance

Question 9

Physical causes of flooding

Answer 9

Intense storms- lead to FLASH FLOODING (exceptionally short lag time)

Prolonged, heavy rain (deep depressions across uk)

Rapid snowmelt- (plains of Siberia)

Question 10

Bangladesh

Answer 10

Flood prone country

Land of flood plains and deltas built up by might rivers (Ganges, Parma and Meghna)

Rivers swollen twice a year by meltwater from himilayas

hilly tracts Bayern rivers often flash flood victims

Question 11

Tidal flooding

Answer 11

Resulting from storm surge

Or when high river flows meet particularly high spring tides in estuaries

Likelihood of flooding also increased by:

Low lying areas with impervious surfaces

Ice dams melt suddenly and water in glacial lakes is released

Volcanic activity generate meltwater beneath ice sheets that is released

Earthquakes cause failure of dams or landslides

Question 12

Human activity and flood risk

Answer 12

Combo of economic and pop growth during 20th caused many flood plains to be built on

Natural landscapes modified for agriculture/ industrial

Sprinkling ground water on arable crops

Ploughing compacts soil

Sewers feed water into channel

River mismanagement:

Channelisation

Dams

River embankments

Question 13

Channelisation

Answer 13

Effective way of improving river discharge and reducing flood risk- simply displaced that risk downstream (location overwhelmed with increased discharge)

Question 14

Dams

Answer 14

Block the flow of sediment down a river so the reservoir gradually fills up with silt- downstream there is increased river bed erosion

Question 15

River embankments

Answer 15

Designed to protect from floods of a given magnitude

Can fail when flood exceed capacity

Question 16

Socioeconomic impacts of flooding

Answer 16

Death and injury

Spread of water borne diseases

Trauma

Damage to property

Destruction of crops

Question 17

Environmental impacts of flooding

Answer 17

There are many positives:

Recharged groundwater stores

Increase connectivity between aquatic habitats

Soil replenishment

Question 18

Eutrophication

Answer 18

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

Caused by removal of soil and sediment by floodwaters

Question 19

Impacts of climate change on inputs and outputs (precipitation)

Answer 19

Water atmos has water holding capacity

Precipitation increase in tropics and high latitudes

Climate warming means more precipitation in northern regions is falling as rain rather than snow

Question 20

Impacts of climate change in inputs and outputs (evaporation and evapotranspiration)

Answer 20

Evap over large areas of Asia and n America appears to be increasing

Transpiration linked to veg changes which in turn is linked to changes in soil moisture and precipitation

Question 21

Impacts of climate change in inputs and outputs (soil moisture)

Answer 21

Uncertain as soil moisture depends on many factors

When precipitation is increasing it is likely that soil moisture will be increasing

Question 22

Impacts of climate change in stores and flows

Answer 22

Surface runoff- more low flows (droughts) and high flows (floods)

Permafrost- deepening of active layer is releasing more groundwater and Meghan released from thawed lakes may be accelerating change

Glacier ice- strong evidence of glacier retreat and ice sheer thinning since 70s and less accumulation as more precip is falling as rain= decreasing store

Oceans- more data on surface temp needed
Where ocean is warming there will be evap
Storage capacity being increased by meltwater
Rising sea level

Question 23

Concerns about short term term oscillations (ENSO CYCLES)

Answer 23

Problem with forecasting- distinguishing between impacts of long term climate change and short term oscillations (el Nino events)

Further complication- ENSO cycles associated with extreme flooding in some parts of world and extreme drought in others

Question 24

Short term climate changes on global water supplies (some of impacts are possible rather than probable)

Answer 24

Diminishing supply, increased uncertainty-

Depleted aquifers leads to groundwater problems

Increase intensity and frequency of droughts as result of global warming and oscillation is issue for rainfed agriculturalists

Greater rates of evapotranspiration- desiccation of forest stores

More frequent cyclone and monsoon events threaten water supplies intermittently