Water EQ2 Flashcards
define the general term drought
an extended period- season, year, several years- of deficient rainfall relative to the statistical multi-year average for a season
define meteorological dought
long term precipitation is lower than normal- effected by atmospheric conditions
define agricultural drought
there is not enough soil moisture to allow enough crops to grow. Caused by precipitation shortages, changes in evapotranspiration rates and reduced levels of groundwater
define hydrological drought
the amount of surface and subsurface water is deficient. Caused by a lack of precipitation or human overuse of water sources
define socio-economic drought
when water demand exceeds water availability. Caused by lack of precipitation or human overuse
define what ENSO refers to
El Nino Southern Oscillation, occurs in the Pacific Ocean with global impacts on weather patterns due to teleconnections
what is the walker cell?
the circulation of air which causes upper atmospheric air to move eastwards and surface air to move westwards across the Pacific resulting in trade winds
What is La Nina?
a phenomena where ‘normal’ conditions intensify.
Low pressure in the west Pacific becomes lower and high pressure in the east grows higher.
Rainfall increases in south east Asia and drought in south America. Trade winds strengthen.
Usually proceeds or follows El Nino
What is El Nino
A reversal of normal conditions occurring roughly every 7 years
Low pressure in the East and high pressure in the West due to warm water shifting Eastward. Heavy rain in south America and drought in south east Asia
How can we measure the change between El Nino and La Nina?
The Southern Oscillation index (SOI) measures strength, direction and speed
air pressure in South America - air pressure in Australia
if there is a sudden drop in the resulting number, El Nino is imminent
why are rainforests struggling to regenerate
positive feedback loop of deforestation and less rainfall
reduced forest cover also reduces soil water storage and evapotranspiration
define a wetland
areas where water covers soil
hydrophytes colonise the area and nutrient rich soil is created
what factors effect the characteristics of a wetland
regional variation in soil topography climate hydrology water chemistry vegetations HUMAN FACTORS
why are wetlands important
Trap floodwater and distribute it across the flood plain
protects against coastal erosion and storm surges
habitat/ complex ecosystems
support the carbon cycle
what are the main causes of water insecurity
Climare variability Industrial water pollution Water contamination from agriculture Salt water encrouchment over abstraction
