EQ2 Flashcards
Types of drought
- meteorological drought
- agricultural drought
- hydrological drought
Meteorological drought
Dry weather patterns dominating an area
Agricultural drought
Lack of moisture in surface soil 2 support plant life
Hydrological drought
Occurs when there’s evidence of low water supply - reservoirs, streams, etc dry up
Normal pacific conditions
Trade winds from east (Peru) to west (Australia)
Warm water pushes west
Upwelling, evaporation, rainfall over the pacific
El Niño event
Trade winds weaken
Ocean current slows
Causing rainfall over S America
La Niña event
Trade winds strengthen
Ocean currents + upwelling stringer
Rainfall over Australia (heavy rain, storms, flash flooding)
S America = droughts
Impacts of drought on ecosystems
Wetlands
Forests
Wetlands
10% of earths surface
Act as water stores, recharge aquifers + trap pollutants
Drought causes less interception, infiltration
Water table falls decreasing the functions performed by wetlands
Wetlands ar quite resilient- plants + soil can adapt well 2 human interference
Forests
Forests are responsible for much of the worlds interception, reducing flooding + overland flow
Drought increases likelihood of fungal diseases in forest pines + threatens their survival
Forests are also resilient but are being tested by human interferences + erratic weather cycles
Meteorological causes = flooding
- Intense storms - w/ short lag time, common in mountainous areas
- Prolonged heavy rain - monsoons/depressions over the UK
- Rapid snowmelt - warmer seasons like Alaska
Flooding is also increased by more general physical factors:
- Topography (low-lying areas w/ impermeable surfaces)
- Volcanic activity = jokulhlaups (ice forms at the top of the volcano + melts when it erupts - realising meltwater own the mountain)
- Earthquake activity rupturing a dam/damaging of a reservoir releases water elsewhere
Human actions + flooding
Channelisation: effective way of improving river discharge + reducing the flood risk. Trouble is that it simply displaces river downstream. Some other locations may well be overwheby increased discharge
Dams: block the flow of sediment down a river - reservoir gradually fills up with silt downstream there’s an increased river bed erosion
River embankments: designed 2 protect from floods of a given magnitude. Fail when a flood exceeds their capacity. Inevitably when this happens- scale of flooding is much greater
Climate change - precipitation (input)
Warmer atmosphere holds more water
Impacts such as increasing rainfall intensity
Geographical area of precipitation increases in tropics + decreases above + below the tropics. Length + frequency of heatwaves increases
Climate change - evaporation (output)
Areas such as Asia + N America see an increase = evaporation, transpiration generally increases too - affecting soil moisture
