Murray Darling Basin

Question 1

How much deforestation has occurred in the Murray Darling Basin?

Answer 1

• 90% of original vegetation has been removed

Question 2

What was the Millenium Drought?

Answer 2

• 12 year period between 1997 and 2009
• Annual rainfall was 12.4% below 20th century average
• Impact felt heaviest in Murray-Darling Basin (agricultural heartland of Australia)
• resulted in disastrous impact on wheat, wool and meat exports
• Caused by culmination of human causes and El Niño stage of ENSO cycle

Question 3

What occurs when the ENSO cycle is in its normal state?

Answer 3

• Air cools and sinks forming areas of high pressure off the coast of South America
• Trade winds blow West
• causes warm water to travel in same direction, away from South America and towards Australia and East Asia
• Upwelling occurs in areas off South America
• Cold water rises to surface as warm water shifts towards Australia
• Warm water accumulates in these areas and evaporates
• creation of low pressure region
• rainfall occurs
• These areas of low and high pressure form the Walker cell
• thus act as part of a single system

Question 4

What occurs when the ENSO cycle is in its El Niño state?

Answer 4

• Trade winds are weakened
• thus warm water moves towards South America, no warm water westward
• creates low pressure zone here
• results in evaporation and relief rainfall in South America due to Andes
• Walker cell is now in opposite direction
• results in high pressure zones over Australasia
• drier, cooler conditions here as air sinks

Question 5

What occurs when the ENSO cycle is in its La Niña state?

Answer 5

• Trade winds are stronger than usual
• results in more warm water accumulating in Australasia
• evaporates, to form low pressure zones
• heavy rainfall occurs here
• Walker cell is in normal direction
• cool air sinks and forms high pressure region in South America
• increased upwelling here as warmer water is shifted more towards Australasia

Question 6

What were the physical causes of the Millenium Drought?

Answer 6

• El Niño events in 2002/3 and 2006/7 and natural climate change cycles due to sunspots enhanced dry conditions
• current warming trends are reducing the temperature gradient between the equator and poles
  
  • results in less energetic storms
  • results in less rainfall
• projected drop of rainfall by 15% by 2030

Question 7

What were the human causes of the Millenium Drought?

Answer 7

• Deforestation:
• 90% of original vegetation removed from MDB since 1800s
• reduced transpiration and precipitation as a result
• increased surface runoff as a result
• increased GW consumption as a result
• potentially lengthened any drought period by 2 weeks per year
• Surface water use:
• 94% of all rainfall evaporates from surface water
• 42% of leftovers are diverted or pumped away for human use through dams and reservoirs
• Emissions:
• anthropogenic GHE add to natural variabilities
• Groundwater over extraction:
• Groundwater accounts for 17% of all accessible water reserves and 30% of all water use,
• farming and herding increases demand

Question 8

Why is there potential for conflict in the MDB?

Answer 8

• 3.5 million people depend on the water supply
  
  • capacity of 32 500 GL per year
• Introduction of water cap and MDBA plan undermined by illegal over use by farmers above quota
• Environmentalists are concerned about wetland water availability for the 16 RAMSAR listed wetlands in the MDB
• Residents in Louth (downstream) are seeing water steadily diminish
  
  • farmers are losing out as well as small businesses who rely on business with residents
  • also results in house prices decreasing
• Brewarrina Fishing community is concerned by currents being reversed due to power of pumps used by large farmers
  
  • are being exploited by farmers who are paying money to essentially keep them quiet
• Clyde & Webster Cotton farms are extracting 30 bn litres of water for their private reservoirs for cotton farming
  
  • own more water than federal government
  • sell water during droughts for exorbitant prices

Question 9

What is the problem with bureaucracy in the MDB?

Answer 9

• MDBA plan was meant to promote equitable water use
• isn’t being followed as there is no meaningful enforcement of quotas
• NSW government is undermining MDBA measures
• allowed farms to use larger pumps than before to extract water
• can essentially run dry low flow rivers
• NSW Government officials are giving more rights to irrigators
  
  • changed laws so now farmers can store buyback water in their reservoirs as well
  • essentially allows them to use tax payer paid water as well
  • makes buyback scheme pointless

Question 10

What does the MDBA plan entail?

Answer 10

• Guides regional authorities, governments and communities on how to sustainably manage river basin
• Aims to ensure that water is shared between all users
• also ensures 2750 GL is returned to river system yearly
• for RAMSAR ecosystems downstream
• MDBA plan reimburses farmers for lost income when sticking to quotas by employing buyback scheme
• farmers are paid by tax payers for the water they don’t use
• $13 bn paid already