Water Lesson 9: Human Cause of Drought Flashcards
Name 3 human causes of drought
Over-abstraction
Building reservoirs and waterways
Changing land use
% of Australia affected by drought each year?
30%
When do most droughts occur in Australia?
Closely linked to El Nino
Causes of drought in Australia?
Record low rainfall
Hot temperatures
What is Day Zero?
Major dams and rivers will no longer be able to supply drinking water to people and agriculture
Other impacts of drought in Australia?
Land becomes orange/red
Windstorms
Decline in agriculture - crops and livestock
Loss of jobs - particularly farmers
Loss of communities
Define wetland
An area of marsh, fen, peatland and water, where natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt
How do wetlands act as temporary water stores?
Mitigate river floods downstream, protect land from destructive erosion and recharge aquifers
How do wetlands maintain water quality?
Wetlands act like giant water filters by trapping and recycling nutrients, as well as pollutants
Other reasons wetlands are important?
-Very high biological productivity and support a very diverse food web, proving nursery areas for fish and refuges for migrating birds.
-For humans they are of huge benefit as both a resource and service
Drought impacts on wetlands?
-Lack of precipitation leads to areas of open water shrinking or drying up
-Extended drying leads to soil erosion as soil moisture is reduced, leading to a reduced ability to store water
-Organic soils may oxidise, releasing carbon
-Some flora and fauna species could be eliminating, creating gaps in the food web in which other species can establish themselves
-Concentrations of dissolved nutrients and pollutants may increase
Drought impacts on rainforests
-Trees become stressed, leading to foliage loss, impairing growth and increased accumulation of pests and diseases
-Younger trees die, reducing the canopy cover
-This reduces humidity, water vapour and therefore rainfall
-Dying vegetation and surface tree litter can easily catch fire
When was the Big Dry in Australia?
1996-2012
% of water provided to agricultural outputs by Murray-Darling Basin?
50%
% of low run-off reservoirs fell to what?
40%
Which city in Australia was most vulnerable due to what % of drinking water coming from the Murray river?
Adelaide, South Australia
40% of water
Location of Pantanal wetlands?
Brazil in the Upper Paraguay river basin, South America
Size of Pantanal wetlands in Brazil?
140 000 km2
Why is the Pantanal wetland so important?
Aquatic and bird wildlife makes it a significant freshwater ecosystem
When is seasonal rainfall in the Pantanal?
November and April
% of Pantanal covered with flooding during rainfall seasons?
80%
% of floodwater retained in Pantanal even in dry years?
60%
Where and when was the Pantanal drought?
Savannah grassland (furthest point from rivers)
2014/15
Effects of drought on the Pantanal?
-Increased tree mortality, which in turn reduced habitats for wild animals
-Wildfires became a major threat, caused by cattle ranchers deliberately setting old grass on fire during the dry season to clear vegetation left un-grazed by their cattle - spread out of control
How long do living trees take to recover from a period of drought?
2-4 years
What species had lower resilience to drought?
Pines which use water at a higher rate
Where are the Pinon Pines?
Four Corners region of south-west USA
When did drought occur in the Pinon Pines?
200-2003
Cause of decline in Pinon Pines?
Severe drought and high temps
What did the Pinon Pines become more susceptible to as a result of the ht dry conditions?
Pine bark beetle attacks
% of pine die-off in some regions?
90%
