the hydrosphere

• Increase in population can be caused by higher birth rates, immigration, or migration within a country
• Per-capita water use increases with affluence, leading to more water consumption for washing and using appliances like washing machines and dishwashers
• Increased irrigation of farmland, especially in commercial agriculture, uses more water than all other human uses combined
• Different industries have varying water requirements, with heavy industries using more water than lighter manufacturing industries
• Deforestation can lead to reduced rainfall reaching the ground and less water returning to the atmosphere through transpiration
• Agricultural activities like compacting soil, crop irrigation, and loss of soil biota can impact water infiltration and retention
• Urban development with impermeable surfaces can increase runoff and contribute to river flooding downstream
• Global climate change affects precipitation patterns, evaporation rates, and wind patterns, leading to changes in water availability
• Construction of reservoirs alters habitats, affects wildlife migration, and changes river regimes downstream
• Over-exploitation of rivers like the Syr Darya and Amu Darya rivers can lead to serious environmental and pollution issues
• Aquifers are important water resources with features like porosity, permeability, and associated geological structures
• Aquifer recharge is essential to maintain water levels, and overexploitation can lead to ecological impacts, saltwater intrusion, subsidence, and reduced supplies
• Monitoring aquifer depletion is crucial, and methods include checking water levels in wells or boreholes and using satellites like GRACE to track changes in water mass
• Examples of over-exploited aquifers include the High Plains Aquifer in the USA, including the Ogallala Aquifer
• The entire Earth is surveyed every 30 days
• Examples of over-exploited aquifers:

  • High Plains Aquifer in the USA, including the Ogollala Aquifer
  • Extends over 450,000km² in mid-west states
  • Important for agriculture and food production relies on aquifer water
  • Aquifer water is largely paleowater (fossil water) recharged during or before the last ice age
  • Long-term abstraction rates for agriculture exceed current recharge rates
• Exploitation of new sources of water:

  • Rainwater collection is important in areas with high consumer demand and reduces urban flooding
  • River water is a convenient source, accessible over a large land area
  • Reservoirs allow storage of surplus water for times of shortage, factors like topography, geology, catchment area, water supply, pollution risk, sedimentation, infrastructure, and existing land use must be considered
  • Estuary barrages create freshwater reservoirs with fewer land use conflicts
  • Desalination of seawater is used in countries with inadequate freshwater supplies
• Sustainable management of water:

  • Artificial recharge of aquifers by diverting surplus water underground
  • River regulation reservoirs maintain river levels during low rainfall and store surplus water to reduce downstream flooding
  • Inter-basin transfers move water from areas with surplus to areas with shortages
  • Afforestation reduces soil erosion and maintains river levels
  • Water conservation methods include low volume uses, xeriscaping, low-volume irrigation, recycling grey water, pollution control, and reduced wastage
• • Distillation involves boiling water to collect steam
• Water treatment processes:

  • Sedimentation allows suspended solids to settle
  • Screens remove debris
  • Aeration ensures high dissolved oxygen content
  • Flocculation/coagulation and clarification neutralize particles and allow settling
  • Filtration removes remaining suspended solids and bacteria
  • Activated carbon filters remove organic chemicals
  • Sterilization methods like chlorine, ozone, or UV light kill pathogens
  • pH control adjusts acidity
  • Fluoridation improves dental health
  • Ion exchange removes toxic ions
  • Reverse osmosis desalinates seawater
• Global demand for water is increasing due to various reasons
• Increase in population can be due to higher birth rates, lower death rates, immigration from other countries, or migration within the same country
• Increase in per-capita water use with increased affluence:

  • In poorer communities without piped water supply, domestic water use is limited
  • As people become more affluent, they use more water for washing and buy appliances like washing machines, dishwashers, and swimming pools
  • Modern appliances may be designed to use less water, but there is still a correlation between affluence and water consumption
• Increased irrigation of farmland:

  • Subsistence agriculture relies on naturally available water
  • Commercial agriculture invests in irrigation schemes using water from aquifers, rivers, or reservoirs
  • Irrigation now uses more water than all other human uses combined
• Industrialisation: different industries have different water requirements. Heavy industry, such as the chemical and steel industries or paper making, use much more water than lighter manufacturing industries. The service industries use very little water apart from the water used by the workers for domestic uses.
• Industrialisation: different industries have different water requirements. Heavy industry, such as the chemical and steel industries or paper making, use much more water than lighter manufacturing industries. The service industries use very little water apart from the water used by the workers for domestic uses.
• Deforestation

  vegetation intercepts rainfall which may evaporate before it reaches the ground. Trees also return a lot of water from the soil to the atmosphere by transpiration. The loss of trees can cause a significant reduction in precipitation in downwind areas as more of the water infiltrates the ground, or runs off into rivers.
• Agriculture

  Soil can be compacted by the use of heavy farm machinery or by livestock trampling.

  Water does not infiltrate easily into compacted soil so soil moisture levels drop and runoff

  Crop irrigation increases evaporation rates.

  The loss of soil biota such as worms reduces infiltration, increases surface runoff and reduces water retention by the soil. 
• Urban development

  Urban areas often have impermeable surfaces such as concrete and tarmac. This reduces infiltration while increasing the rate of runoff. Rapid runoff from large urban areas can increase river flooding downstream.
• Higher global temperatures affect rates of melting, evaporation, and condensation as well as wind patterns
• These changes combine to alter the type, amount, timing, and location of precipitation
• More rapid melting of snow and ice is caused by the warming associated with global climate change
• Snowfall in cold weather and its later melting in warm weather reduces extremes in river flow
• Loss of ice may increase flooding after heavy rain and low river flow during periods of rainfall
• Changes in evaporation, temperature, and wind velocity/direction will change the timing, type, and amount of precipitation
• Construction of a dam and reservoir alters the environment of the reservoir site and the surrounding area
• Habitat change:

  • Flooding the reservoir destroys previous habitats but creates new valuable ones
  • Reservoir may be more valuable than what has been lost, especially for wetlands
• Wildlife barriers:

  • Dam and reservoir act as a barrier to wildlife migration along the river, such as salmon and sturgeon
  • Free movement along the river is important for recolonising vacant areas in bad years, which the dam may prevent
• River regime downstream of dams:

  • Reservoir may be used to regulate river flow by holding water back during surplus times to ensure adequate flow during shortages
  • This reduces flooding risk downstream but also reduces lower flow periods important for species like river turtles and salmon/trout
  • Changes in flow fluctuations can impact river erosion, sedimentation, and meander development
• Sedimentation:

  • Sediments carried into the reservoir settle there instead of being carried downstream
  • In the past, sediments fertilised floodplains downstream and built up river banks and coastlines
  • Counteracted erosion