Water Cycle Pack H Flashcards
How can seasonal variation cause water deficits?
- In summer, it is hotter and drier
- There is more evaporation and transpiration
- More recreational and agricultural water use
How do El Nino and La Nina cause water deficits?
El Nino:
- Strongest El Nino was in the water of 1997/98
- Resulted in extreme weather around the world
- Drought conditions in Indonesia, Malaysia and E/SE Asia
- Summer temperatures were over 40°C in Mongolia
- Drought in Mozambique
- One of the wettest seasons on record in Kenya
La Nina;
- Horn of Africa during the 2010 event
- Suffered the worst drought in over 60 years
- There were major crop losses, death of livestock and reduced milk production
What is a drought?
A shortfall of deficiency of water over an extended period of time usually at least a season
What is a meteorological drought?
An extended period of lower than average rainfall for a region
What is an agricultural drought?
Insufficient moisture to maintain crop yields
What is a hydrological drought?
Shortages in water supplies in surface and groundwater stores
What is a famine drought?
When the lack of water causes food shortages to the extent a famine is caused
Why is drought common in Australia?
- There are recurrent droughts and 30% of Australia suffers each year
- Low and highly variable rainfall totals
- Droughts are intense and short lived, both local and larger
- The Big Dry was a 1 in 1000 drought which began in 2006 and covered large areas of Australia
- Usually connected with El Nino
- Climate change is causing an impact, as the SE is warmer and drier
- Reservoirs were 40% full in 2016
- Murray river was over-extracted so it couldn’t reach the sea
- Has one of the highest water consumption rates per capita in the world due to the affluent population and water-consuming lifestyle
Why is drought common in the Sahel and how have humans made it worse?
- Rainfall in 100mm in the N and 800mm in the S
- There is a transitional climate zone between the desert and savanna
- Large variability year to year
- Drought can come from warmer tropical seas which lead to air uplift over the oceans and less rain on land
- Human populations are vulnerable due to poverty, subsistence farms and rain-fed crops
- This exacerbates the effects leading to famine
- Seasons and El Nino cause yearly dry periods
What was the world’s first climate change drought?
- Madagascar famine drought in 2011
- Cause by prolonged lack of rain and climate change
- Climate change meant that vegetation and crops died and it became hotter and drier
What drought happened in Lake Chad?
- One of the world’s largest water bodies which is disappearing due to climate change and population pressures
- Surrounded by Cameroon, Chad, Niger and Nigeria
- Shrunk by 90%
- From 25,000km2 in 1963 to less than 1,500km2 in 2001
- 30 million people in the region compete over water
- Leads to migration and conflicts
- Climate change and evaporation leads to water table decreasing
- Roots don’t reach water so vegetation dies
- Increased runoff and decreased photosynthesis increases CO2 and causes a feedback loop
How has surface water extraction in California led to water shortages?
- 100x more water is needed now than in the 1920s
- Due to a population increase and increased standard of living
- Agricultural, domestic and industrial use have increased
What are the causes of water deficits in California?
- Uneven distribution of rain in California
- N has a surplus while the S had a deficit
- Aqueducts move water from the mountains/N to the S
What are droughts like in California?
- Gets all 3 types of drought (meteorological, agricultural, hydrological)
- Has had a meteorological drought for a decade
- Colorado River’s discharge is decreasing and Lake Mead is lowering (putting HEP at a risk)
- Snowfall is decreasing due to La Nina and the drier/hotter conditions now in the S
- Soil water is lost from the 40°C temperatures in the summer
Why is there such high water demand in California?
- Large urban demands from LA, San Diego and San Francisco and their domestic/industrial uses
- 80& of water use if for agriculture as large areas only get less than 150mm per year
- Irrigation systems allow crops in dry areas (e.g. almonds, citrus fruit grapes, flowers vegetables)
- Farmers need more irrigation water, which is expensive
What are the environmental impacts of drought in California?
- Wetlands are being rained or are drying up
- Species are lost
- Salinisation is occurring from water evaporating and leaving a layer of salt on the soil surface which kills crops
- Land subsidence is damaging infrastructure as a result of water being extracted from underground sources
What are the economic and social impacts of drought in California?
- More freshwater used by farmers
- Water is being more expensive
- Too expensive to grow rice in many areas
- Water bills are rising for households
What are the solutions for drought in California?
- Desalination using sea water, which consumes a lot of energy and is expensive
- Drought resistant plants which require less water
- Recycling of wastewater
- Flood water storage under cities to replenish aquifers
