EQ2 5.4 DEFICITS IN THE HYDROLOGICAL SYSTEM LEAD TO DROUGHT Flashcards
what are the 4 types of drought
meteorological, agricultural, hydrological, socio-economic
meteorological drought
this type of drought presents a degree of dryness compared to what is considered to be normal precipitation levels for that area, climate and season.
agricultural drought
when there is insufficient water for crops, leading to wilting or loss of crops without irrigation.
hydrological drought
when the drainage basin suffers shortfalls such as reduced streamflow or an increase of river flow into the reservoirs.
Socio-economic drought
when there is a demand for water to be used for social and economic purposes such as crop irrigation or when HEP exceeds water availability.
drought
Drought happens when an area suffers from a water deficit. If rainfall falls well below average for a specific place then a deficit can happen.
what are ENSO cycles
(El Niño Southern Oscillation) refer to the El Niño and La Niña changes in the Pacific Ocean.
what happens in El Niño in south america
El Niño events happen every 3-5 years, where winds weaken across the South Pacific Ocean and reverse direction. Warm water moves to the South American coastline, where lower air pressure causes large increases in rainfall, promoting the potential for flooding.
what happens in El Niño in Australasia
During El Niño, Australasia has cooler than normal ocean temperatures and is subject to high air pressure, resulting in little rainfall and an increased risk of drought.
what happens in La Niña in Australia
During La Niña years, low air pressure descends on Southeast Asia and Australia leading to increased rainfall and risk of flooding.
what happens in La Niña in south america
South America receives high air pressure, which leads to reduced rainfall and increased likelihood of drought.
Short-term precipitation deficit
There can be a short-term precipitation deficit in places when the cycle that creates clouds is interrupted.
A water deficit may be experienced in areas that are used to low air pressure systems and have a change of weather front to experience a high air pressure system. The cool sinking air in high air pressure systems does not have the ability to form clouds and produce precipitation.
what are the main human activities associated with drought
over-abstraction of surface water and aquifers
Brazil over abstraction
In 2014-15 industries, farmers and domestic users in Brazil increasingly used groundwater, until the rivers began to run low.
Poor and rural communities suffered because they only had access to groundwater because of rivers running low.
causes of over-abstraction in Brazil
Brazil’s government introduced a charge for drilling wells of around US$35,000- US$100,000.
Residents drilled illegally because they could not afford the charge, meaning the water abstracted was not monitored.
Hydrologists believe that the government’s official records of wells drilled in 2014 only represent a 1/3 of the total, as 70% of wells were illegal.
problems with over abstraction in Brazil
The government’s well charge resulted in illegal drilling.
Illegal wells are shallower and so have not percolated deep into the bedrock. Water from illegal wells is less filtered by bedrock and may contain industrial and agricultural pollutants with higher levels of bacteria.
An increase in poor sanitation and water-borne diseases happens if the water is not filtered further.
what does drought lead to
Drought leads to less water for the vegetation of an area. This can have devastating effects on an flora and fauna that interact in that ecosystem.
Ecosystem functioning
the biological, chemical and physical processes that take place in an ecosystem.
Ecosystem resilience
how capable the ecosystem is of surviving changing water levels.
which areas are more resilient to drought
deserts and semi-arid areas
the impact of drought on rainforests
Prolonged periods of drought lead to forest stress.
Younger trees die as a result of drought. This reduces the canopy cover.
Reduction of canopy cover leads to less interception and infiltration but also decreases evapotranspiration. This means water vapour and rainfall reduces.
the impact of drought on forests
Forests that are exposed to tropical sunlight with dead vegetation and a mass of dry organic material can easily set alight.
Lightning storms and high winds can then turn a small fire into a wildfire.
the impact of drought in the forests of Croatia
Croatia suffered from 2 ½ months of no rainfall during the summer of 2017. This lead to widespread drought and ultimately wildfires that were challenging to manage. Water-bombing planes were donated from nearby countries to control the flames.
the impact of drought on wetlands
Drought increases the likelihood of tree mortality.
A decrease in vegetation reduces the habitat for both wild or farm animals. Birds and wetland vegetation respond to drought differently. Drought can change communities by eliminating species and having knock-on impacts on the rest of the food chain.
The likelihood of wildfire increases.
the impact of drought on wetlands in Suffolk
In Minsmere, Suffolk, wetlands species such as snipe and thrush are impacted by the dry soil surface which is present during a drought.
The snipe and thrush are less able to penetrate the dry soil to reach the invertebrates they feed off.
