Geography Water Cycle Case Studies

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Human disruption to the Water Cycle in Amazonia

  • In tropical rainforests such as those found in Amazonia, the dense canopies of vegetation mean that rates of interception and evapotranspiration are high
  • This causes high humidity and heavy local convectional rainfall and is an example of a self sustaining cycle
  • Evaporation from the forest is also important in sustaining regional rainfall in areas around the periphery of the tropical rainforest which is important to key agricultural regions
  • Research suggests that in the Amazon basin deforestation may be significantly reducing evapotranspiration and precipitation, while increasing run-off and river discharge
  • An example being that the Tocantins River showed a 25% increase in river discharge between 1960 and 1997, coincident with increased deforestation 
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Drought in the Sahel, Africa 1

  • The Sahel is a vast semi-arid region across Africa at the southern edge of the Sahara desert, coving parts of 11 countries. 
  • People living in the region usually cope with the semi-arid conditions but occasionally severe droughts occur making it difficult for them to adapt and survive 
  • Since the late 1960s there has been a pronounced decline in annual rainfall
  • The most recent severe drought occured in 2011-12 
  • There have been studies that suject the causes of the Sahelian drought is a combination of physical and human factors 
  • In 2002 a study by the CSIRO suggested that the Sahel droughts of the late 20th century was caused by air pollution (aerosols) generated in Europe and North America. These pollutants are thought to have caused atmospheric cooling, changing the global heat budget and atmospheric circulation so that tropical rains did not arrive, causing drought
  • In 2005 a climate modelling study by NOAA indicated that the late 20th century Sahel drought could be the result of higher sea temperatures caused by anthropogenic climate warming. The rain-bearing winds that move over the Sahel appear to fail when the sea surface temps in the tropical Atlantic Ocean are warmer than average.
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Drought in the Sahel, Africa 2

  • Professr Adam Scaife of the Met Office forecast that the 2015/6 El Nino event would increase water stress in western Sahel, where temperatures were 2 degrees higher than average in December 15 and January 16, with lower rainfall.
  • A pulse of easterly winds the Pacific caused effects in other world regions, and cooler waters in the North Atlantic added to the added to the drying conditions with reduced evaporation.
  • The Sahel region has one of the highest poverty rates and lowest development levels levels, with countries experiencing some of the highest population growth rates in the world.
  • The demand for food and fuel wood is therefore accelerating, and the natural dryland ecosystems are progressively being converted into farmland, which is being over cultivated and overgrazed, causing desertification. 
  • Where effects of reduced rainfall and human pressures are combined, there is reduced vegetationcover and soil moisture, which may create self perpulating severe droughts 
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The millennium drought in south eastern Australia,

  • The millennium Drought was the longest uninterrupted series of years with below median rainfall in south eastern Australia since at least 1900 with the average rainfall 12.4% below mean.
  • The drought was the result of multiple physical and human causes 
  • El Nino events in 2002-3 and 2006-7 were partially responsible, research indicating that prevailing El Nino conditions explained about two thirds of the rainfall deficit.
  • Strengthening of the high pressure belt (STR) is estimated to account for 80% of rainfall decline 
  • This ridge of high pressure blocked storm tracks (depressions), forcing them towards higher latitudes and thereby reducing frontal rainfall
  • Simulations of global climate change was only able to reproduce STR strengthening when human emissions of greenhouse gases were included.
  • It is thought that anthroprogenic warming is reducing the temperature gradient between the Equator and the pole, which would reduce the energy available for mid latitude storm systems and the polar fron jet stream 
  • There is insufficient evidence to prove this relationship.
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The impact of the 2015-16 Floods in the UK

The 2015-16 UK winter floods were caused by a series of storm events (depressions) that created intense heavy rainfall and widespread flooding 

Storm Desmond

  • Brought severe gales  and heavy rain to the UK in early December 2015, this lead to localised flooding in North-West england, southern Scotland, north Wales and northern Ireland. cumbria was worst hit with one months rainfall in a day, the river exceeded the highest discharge levels ever recorded.
  • Honister in cumbria recieved 341.1mm of rain in 24 hours 
  • Storm Desmond involved very low air pressure - 946 millibars and its front brought exceptionally prolonged and heavy rainfall as the air was forced to rise across high ground.
  • Conventional and orographic precipitation was combined and together with already saturated ground, this created conditions for extreme flooding 
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The impact of the 2015-16 Floods in the UK

Strom Eva brought heavy rain over Christmas 2015, on boxing day residents in West Yorkshire and lancashire were evacuated

Storm Frank followed at the end of 2015, bringing storms and severe gales to western parts of the UK

  • A number of human factors increased the flood risk from these storm events. The soils and rock were already saturated by previous heavy rainfall in November from the passage of storm Abigail and the remains of hurricane Kate
  • New flood defences failed in cities in northern England when they couldnt with the river flows, and even prolonging the flooding by holding the water up.

Impacts of Storm Desmond

  • Storm Desmond caused heavy rain and flooding of homes and infrastructure, as well as extensive disruption to travel and evacuation of properties.
  • 5,200 homes affected, 2 deaths related to flooding, 40 schools closed, power cuts, the government provided £50 million to Cumbria and Lancashire county council
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The impact of the 2015-16 Floods in the UK

Impacts of Storm Eva

  • 9,000 properties were flooded, 7,574 homes across northern England affected by powercuts, explosions where gas mains ruptured, M62 closed, football fixtures cancelled. Emergency measures to reduce floodwaters included the transportation of 20 water pumps and the installation of 2 km of tempory flood barriers 

Impacts of Storm frank

  • Transport disruption to road, rail and air transport, more than 300 properties evacuated, powercuts, school closures, one death due to the floods

Overall impacts 

  • 16,000 properties flooded, £24 millions spent on emergency payments to households and buisnesses, 3,000 families helped into alternative accommodation, average cost of a domestic property flood claim was £50,000, the government announced £200 million in additional funding, they also committed £2.3 billion for flood management projects over the next 6 years. Total economic cost of the floods estimated £5 billion 
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Saltwater encroachment in the Pacific Islands

  • Many of the small, low lying Pacific Islands depend on small aquifers for their freshwater supply; for example, 35% of Samoas water supply is drawn from aquifers.
  • The aquifers are increasingly threatened by saltwater intrusion as a result of over-abstraction, climate variability and sea level rise 
  • Population growthhas increased water demand, resulting in an increase ingroungwater pumping and consequent lowering of the water table 
  • Climate variability associated with ENSO cycles is causing rrecurrent droughts and floods.
  • Crop production depends on freshwater irrigation, making saltwater intrusions a serious threat to health, food security and livelihoods.
  • This is one reason why some island communities are considering completely relocating to other countries, such as Kiribati to New Zeland.
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River Nile trans boundary water conflicts 1

  • The 6,700km long river Nile is the longest river in the world and flows through several countries. It is an international transboundary river, whose water resources are shared by 11 countries - Tanzania, Uganda, Rwanda, Burundi, Congo-Kinshasa, Kenya, Ethiopia, Eritrea, South Sudan and Egypt.
  • The Nile has two major tributaries the White Nile and the Blue Nile
  • Much of the river and its tributaries flow through semi arid and arid areas, which increase their importance as other water resources are scarce.
  • This river is an increasingly valuable resource for these Nile countries, providing water for domestic, industrial and agricultural purposes and its under increasing pressure from rapid population growth, economic development and climate change.
  • The river is particularly important to Egypt and Sudan where its primary water source.
  • Egypt depends on the River Nile for 95% of its water needs
  •  In 1929 a Nile agreement between Egypt and the UK (the colonial power in Sudan at that time) granted significant water allocations to Egypt and Sudan, making no allowance fot the water needs of the other Nile states 
  • It also granted Egypt veto power over construction projects on the Nile and its tributaries
  • This agreement had led to conflicts between Nile river basin countries, upstream countries are increasingly harvesting water to meet demands of growing pops and econamies 
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River Nile trans boundary water conflicts 2

  • In 1999, the River Nile countries, except Eritrea, signed the Nile Basin Initiative (NBI) in an effort to enhance cooperation over the use of the Nile water resources. 
  • In 2010, Burundi, Ethiopia, Kenya, Rwanda, Tanzania and Uganda signed the CFA agreement on sharing Nile Water which raised strong opposition from Egypt and Sudan over fears it would reduce their water right and allocations
  • In April 2011 the Ethiopian Prime Minister announced the construction of the Grand Ethiopia Renaissance Dam on the Blue Nile, which met with an angry response fromt the Egyption president. 
  • The disagreements led to discussions with then led to an agreement that is expected to resolve some of the issues between Ethiopia and Egypt; in March 2015 Egypt, Ethiopia and Sudan met and signed an agreement on the development of the Grand Renaissance Dam
  • However this agreement did not resolve the broader, contentious issues of sharing the Nile waters among all Nile countries, as shown by Egypt not signing the CFA 
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Conflict between water users in Ethiopia

  • Ethiopia has an ambitious and controversial dam-building programme, designed to turn the country into the 'powerhouse of Africa' and fuel economic growth
  • The programme has not only caused conflict but has also caused significant internal conflict, such as controversy over Gilgel Gibe III Dam
  • The Gilgel Gibe III Dam and hydroelectric power plant is on the Omo river in Ethiopia. This US$1.8 billion project began in 2008 and started to generate electrisity in October 15, becoming the third largest hydroelectric plant in Africa
  • The environmental impact assessment was not published until two years after construction started, according to critics, the dam will be potentially devestating to the downstream indigenous population as it will prevent seasonal floods 
  • It is estimated that more than 200,000 people rely on the Omo river below the dam for subsistence agriculture, and they rely on the seasonal floods 
  • The dam not only threatens their livelihoods but there survival
  • Those supporting the dam argue that artificial floods can be relseased by the dam and irrigation projects are planned 
  • Critics belive it will only benefit state-owned companies, there are reports of human rights violations by the Ethiopian army against locals who oppose the sugar plantations in the valley
  • In June 11, UNESCO's World Heritage Committee called for the construction to be haulted, to review its impact on Lake Turkana. It is feared that the dam could reduce the level of the lake by up to 10m, affecting up to 300,000 people as well as wildlife. This could increase the salinity of the water, threatening drinking water, the fishing industry and the lake ecosystem
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China's South-North water transfer

  • Northern China is suffering from water scarcity
  • Half of China's people and two thirds of the farmland are in the north of the country while 80% of the water in the south
  • Bejing has similar levels of water scarcity to Saudi Arabia, just 100 cubic metres per person a year
  • The water table under the capital has fallen by 300 metres since the 1970s, the problem is compounded by poor water qualityin up to 60% of river water as a result of pollution
  • China has designed a huge hard-engineering solution, the largest inter-basin water transfer scheme in the world: the South-North Water Tranfer Project. 
  • This project has the capicity to deliver 25 billion m^3 of freshwater per year from the Yangtze river.
  • The project has raised a number of concerns, economically its expensive, construction costs of US$80 billion with high maintenance costs and water prices  
  • Socially, more than 300,000 people were displaced by the rising water and construction
  • Environmnetally, the tranfer of water does not address the water shortages in the north. Pollution is a major factor
  • Frequents droughts in the Yangtze basin caused droughts in the south. The project would increase risk of more frequent scarcity.
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Water Management 1

Sustainable water water management schemes in Singapore 

  • Singapore is a city state with an area of only 710km^2 and a population 5.4 million
  • Receives abundant rainfall (2,400mm per yer).
  • However because of the limited land for collection and storage of water, high evaporation rate due to tropical climate and the lack of groundwater resources, Singapore is considered to have water scarcity 
  • Singapores national water agency (PUB) has invested in research and technology to create a diversified water supply, comprising local catchment water, imported and recycled water
  • Local catchment water involves collecting rainwater through drains, canals, rivers, storm water and reservoirs before it is treated to supply drinking water
  • Singapore has an agreement until 2061 to import water from Malaysia
  • NEWater is a high grade recycled water produced from used water that is treated and further purified using advanced membrane technologies and ultraviolet disinfectio, making it ultra clean and safe to drink
  • Singapores 4 NEWater plants can meet up to 30% of the water needs, by 2060 PUB aims to meet 55% of water needs 
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Water Management 2

Smart irrigation in China and Australia

  • Smart irrigation provides crops with a suboptimal water supply causing mild stress during crop growth stage that are less sensitive to moisture deficiency.
  • This technique has been found to conserve water without a significant reduction in yield.
  • A study of winter wheat production on the North China plain showed water savings of 25% or more through the application of smart irrigation, combined with acceptably high yields and net profits
  • In Australia, regulated smarrt irrigation of fruit trees increased water productivity by approximately 60%, with a gain increase of fruit quality and no loss in yield. Controlled irrigation, such as drip feed, ensures that water goes directly into the soil next to the roots of crops, which prevents evaporation losses
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Water Management 3

Rainwater harvesting jars in Uganda 

  • Wateraid is an international non-government oraganisation that raises funds to improve access to safe water, sanitation and hygine for some of the worlds poorest people
  • An example of their work can be seen Kitayita village, Uganda, where 3,000 people lack access to safe water. 
  • Local builders have been trained in the construction of rainwater harvesting jars, which are made from locally available materials and have a capasity of 1,500 litres.
  • They are usually designed to collect rainwater from roofs and store water for drier periods 
  • The objective has been to help the community contruct on site water supplies, close to home, removing the need for old or infirm people to travel long distances across difficult terrain to collect water 
  • The jars have a long life, and once constructed can provide a stable water source for many years 
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