Water

• The hydrological cycle is driven by gravitational potential energy and solar energy
• Transpiration - plants absorb water through their roots, which then evaporates into the atmosphere via stomata on leaves.
• The Global Water Budget is the balance of fluxes and size of water stores over a one year period
• Causes of Drought

  • Short term Causes: blocking anticyclones, reduced soil moisture
  • Mid-term Causes: El Nino, hydrological - reduced amounts of water in rivers
  • Long-Term Causes: Global Atmospheric Circulation creating hot and cold deserts through descending air at Ferrel, Hadley and polar cells, Climate Change
• Outputs of the hydrological cycle include evaporation, evapotranspiration, and channel flow
• Physical influences on the water cycle include climate, vegetation, soils, geology, and relief
• Human disruption to the water cycle includes: abstracting water, reservoir creation, deforestation and land use change
• Ecosystems vulnerable to drought


  • Wetlands
  • Forests
• Impacts of drought on Wetlands


  • Conditions are adapted to the presence of water
  • If conditions become drier they are increasingly vulnerable
  • May increase soil erosion
  • Reduce ability to absorb floodwaters
  • Reduce water sources
  • May cause the oxidation of soils, releasing carbon into the atmosphere
  • Species are at risk of habitat loss
• Impacts of drought on Forests

  • Droughts will slow growth and cause stress
  • Trees may lose leaves and be unable to photosynthesize, so they die
  • It can take 2-4 years for a tree to recover from drought conditions
  • Weakening of trees mean they can be attacked more easily by pests and diseases
  • Leading to further loss of habitats
• Pressures of water insecurity include:

  • Increased population
  • economic development
  • farming
  • better standards of living
• Economic water scarcity arises from a lack of affordability, lack of financial ability to develop them, and poor management of supply and use
• Causes of water insecurity:

  • over-abstraction of surface and groundwater sources
  • contamination by farming and industry
  • climate change
  • salt water encroachment
  • climate variability
• Meteorological causes of flooding:

  • intense storms
  • snowmelt
  • prolonged rainfall
  • monsoon rain
  • heavy rainfall
• By 2025, the UN predicts that 1.8 billion people could be facing water scarcity
• By 2030, the UN predicts that 40% of the world will experience water deficit
• The UN predicts that 40% of the world's population depend on trans-boundary water supplies, and with over half of these agreements there is no international agreement
• Hard engineering schemes include:

  • water transfer in China
  • mega dams in Three Gorges Dam in China
  • desalination in Israel
• Sustainable water schemes include:

  • restoring water supplies
  • water conservation
  • water recycling
  • GM Crops

  Case Study: Singapore
• The Water Poverty Index focuses on 5 components:

  • water resources
  • access to water
  • handling capacity
  • use of water
  • environmental indicators- ability to sustain ecosystems
• The Integrated Water Resource Management approach is a holistic approach to protect the environment and ensure fair distribution:

  • freedom from corruption
  • environmental protection of all supplies and ecosystems
  • food and water security for poorer people
  • effective communication between people
  • decentralised approach
  • Effective regulation and planning use
• Amazonia river

  • contains worlds largest area of tropical rainforest
  • disrupted through deforestation
  • lowering of humidities leading to less precipitation, more surface runoff and infiltration, more evaporation and less transpiration, more soil erosion and silt fed into rivers
  • generates 20% worlds oxygen and freshwater discharge
  • stores 100 billion tonnes of carbon
• Desertification- The Sahel

  Causes:

  • climate- high seasonality and variability, persistent lack of rain, lack of rain plus pressure on land leads to increased rates of desertification, 80% drylands suffered from environmental deteriation
  • Deforestation- catalyst of soil erosion and albedo changes, vegetation loss , higher albedo , evaporates water vapour which reduces potential for rain
  • Rainfed agriculture accounts for 95% of cultivated area
  • population growth
• Desertification- The Sahel

  Characteristics:

  • stretches from Mauritania to Ethiopia
  • 11 countries
  • high poverty, low development, high population growth
  • since late 1960s rainfall decreased significantly
  • high agricultural sector
  • would benefit from afforestation- prevents water runoff and has vegetation to further support the cycle
  • more than 1.8 billion trees located- improving microclimate, drought resilience, carbon storage and soil health
• Millenium Drought 1997-2009

  • one of worst droughts for south east Australia
  • El Nino explained 2/3 of rainfall deficit
  • water restrictions in major cities, increased electricity prices
  • major bushfires 2009
  • cattle farming not good land use as it increases demand and there is less supply in El Nino meaning cattle died as there was not enough water for them to drink and to grow their food
• UK Flood Events 2007

  • Tewksbury
  • natural factors- extreme and persistent rainfall, River Severn and Avon convergence which led to them overflowing their banks, surrounding hills created more runoff
  • human factors- urban development creating impermeable surfaces, flood defences were inadequate for this event , land use change including agricultural practices in the catchment area
• Impacts of 2007 UK floods

  Social:

  • over 3500 homes evacuated
  • health risks- waterborne diseases
  • limited access to healthcare Economic:
  • Cost of damage millions of pounds
  • large disruption to local businesses
  • aftermath saw surge in insurance claims and need for investment into reconstruction and recovery efforts Environmental:
  • local ecosystems damaged
  • water pollution increase, sewage contamination
  • long term changes in landscape and an alteration in the course of local rivers
• Physical Cause of water insecurity- Mekong Delta, Vietnam

  • saltwater encroachment
  • 800,000 hectares of rice may be affected
  • water with a salt content of 0.4% found 30 km inland
  • over-abstraction - drought, incursion up to 60km inland
  • residents asked for £12.2 million to pump freshwater to various sources to mitigate impacts of drought
• Human Causes of Drought- Mexico City

  • population of 22.5 million
  • 2021 drought impacted 80%
  • Rain does not fix the problem
  • poor infrastructure
  • Over-abstraction causing 50cm sink in aquifers
  • takes water from other communities to maintain a system that causes issues for indigenous communities
  • 40% water lost through leakages
  • 73% population relied on bottled drinking water
  • 6th most dangerous country to be environmentally impacted
  • economic water scarcity
• Trans-boundary water conflict- The Nile

  • 10 countries share the basin
  • approximately 160 million people depend on the Nile
  • 300 million people in basin countries- population expected to double in next 25 years, adding to demand
  • All basin countries, apart from Kenya and Eygpt, are among the 50 most poorest nations- increasing risk of famine and disease
• Hard Engineering Schemes- 3 Gorges Dam, China

  • HEP dam on Yangtzee River
• Hard Engineering Schemes- 3 Gorges Dam, China

  • HEP dam on Yangtzee river
  • worlds largest power station
  • cost $30 billion
  • over 100 towns submerged in construction
• 3 Gorges Dam: benefits and drawbacks

  Benefits:

  • winners include China's emerging middle class and industry
  • controls water level which avoids frequent floods
  • tourism Drawbacks:
  • 1.1 million people to be resettled
  • built near geological fault lines- landslides may increase
  • huge environmental impacts- endangering over 80 species
• South-North Water Transfer:

  • $62 billion project
  • estimated 330,000 people relocated
  • saves China from water crises that could set development back years
  • vital for economic development
  • about 345,000 villages displaced
• Sustainable Schemes: Singapore

  • city state
  • few natural water resources
  • thriving economy and high standard of living
  • water management top priority with 6 million inhabitants
  • 3 key strategies include: water conservation- education on careful water use, green roof spaces, recycling of water- accounts for 40% of water, desalination- 2 plants now meet 25% of demand
• Integrated Drainage Basin Management- Colorado River

  • 97% in USA, 3% in Mexico
  • source- Colorado mountains, mouth- Gulf of California
  • precipitation variable, prone to drought
  • average flow decreased by 15% since 1990
  • challenges include: increased urbanisation, population growth, increased agricultural irrigation needs, Southern California with no major rivers
  • 1944 Mexico given access to allocated water- evidence of superpower status of US
  • Many agreement as water increasingly did not meet demand
  • 2012 Minute 139 gave Mexico right to store water in River Mead
• 1996 Helsinki UN Water Convention on the Protection and Use of Transboundary Watercourses and International Lakes

  • encourages use of water in reasonable and equitable way
  • ensure sustainable management
  • countries must cooperate and enter agreements
  • it is a framework and can only further establishment and implementation of existing agreements
• The Berlin Water Framework Directive and Hydropower is a European initiative consisting on 9 water management principles, enshrined in international law including:

  • management maximising availability and reliability of water supplies
  • river basins managed in an integrated way
  • long term planning of needs
  • minimising environmental damage
  • cooperation of countries or regions
  • everyone recieving fair share
  • difficult to implement
• The Paris Agreement is a legally binding international treaty to reduce greenhouse gas emissions to prevent climate change. The aim is to keep global temperature rise well below 2 degrees above pre-industrial levels.