Water and carbon

• Fen bogs: peatland created due to the saturation of a high water table. (springs)
• raised bogs: bogs formed from the runoff of precipitation.
• blanket bogs: formed due to relentless precipitation as a result of orographic factors
• positive feedbacks: Peatlands, ocean loss, albedo effect, invasive species, wildfires.
• negative feedback: greater evaporation leads to greater cloud cover, greater vegetation growth in areas where previously it was too cold.
• Global hydrological cycle is a closed system: no external inputs/ outputs.
• Residence time: the average time a water molecule will spend in a store. (It is more susceptible to pollution if it is in situ for a longer period of time.)
• Some stores have such high residency times they are non-renewable. (e.g. fossil water, deep ancient groundwater or melted cryosphere).
• Factors affecting the distribution of stores:

  ·       Climate 

  ·       Geology 

  ·       Drainage basins

  ·       Biomass size and storage 
• Accumulation: the build-up of snow and ice that takes place in the cryosphere.
• Ablation: the change from solid ice (glacier or sea ice) to liquid. (melting)
• Drainage basins are subsystems within the global hydrological cycle. (an open system).
• Frontal precipitation: a warm front of air and a cold front of air collide and the warm moist front is forced up above the cold front. 
• Orographic precipitation: warm moist air is forced up over extreme landscapes such as mountains or hills leading to it cooling and condensing. The rain will usually only fall on the windward side of the mountain range leading to a dry, rain shadow region on the lee side of the mountain.
• Storm hydrographs 

  Graph used to measure the changes in the rivers discharge after the event of a storm.
• River regimes

  The difference in discharge of the river throughout the year.
• Baseflow: the water that reaches the channel through throughflow throughout permeable rock. 

  Channel flow: water through the river aka discharge.

  Overland flow: water that flows over saturated land before it can infiltrate or enter the watercourse.
•  

  Discharge: cross section area x mean velocity of river At a particular point in the river.
• Flashy storm hydrographs: steep limbs, high discharge, very short lag times.
• Flat hydrograph: gentle limbs, low peak and longer lag times.
• Factors leading to flashy hydrography

  Deforestation​

  Urbanisation​

  Steep sloping valley​

  Clay Soil​

  Heavy or prolonged periods of rainfall​

  Winter

   
• Factors leading to flat hydrograph 

  Afforestation​

  Fields - No or little urbanisation​

  Gently sloping valley​

  Sandy Soil​

  Low rainfall​

  Reservoir or Dam upstream​

  Summer

   
•  

  Collision: small droplets collide with other small droplets and coalesce (stick) leading to larger droplets and faster falling. Occurs in warm, humid clouds containing water droplets.
• Bergeron Findeisen: water condenses onto ice particles or other small nuclei. When large enough they fall and either melt and fall as rain or fall as snow. Occurs at high altitudes or freezing climates but depends on a mixture of ice and water.
•  

  Causes of excess runoff (overland flow):

  1)     Amount/ type of rain. Excessive snowmelt may not allow time for infiltration.

  2)     Vegetation 

  3)     Geology 

  4)     Snowmelt 

  5)     Antecedent conditions 

  6)     Drainage density 

  7)     Size and shape of basin.
• Human causes of excess run off:

  1)     Climate change 

  2)     Floodplain drainage 

  3)     River management 

  4)     Changes of land use (agriculture) 

  5)     Urbanisation 

  6)     Deforestation 
• Monsoon rains.

  The seasonal prevailing wind in the region of south and SE Asia blowing from the south west between may and September and brining rain or from the NE between October and April bringing drought.
• ITCZ- Inter tropical convergence zone.
•  

  ITCZ- Inter tropical convergence zone.

  A band of low pressure that generally lies near the equator. Follows the sun in the persition it moves seasonally from north in the northern hemisphere summer (June) and south in the southern hemisphere summer (December). Created by solar isolation. 
• El Niño and La Niña: the two party the ENSO cycle (El Nino Southern Oscillation)
• El Nino is the reversal of trade winds and the creation of high pressure on Australia’s coast and heavy rain on south Americas. 

  La Nina is an extreme of the normal and leads to drought across south America.
• Cape town

   

  Day 0= water supply of cape town to be turned off forcing residents to que for water.

  Caused by record droughts and population growth. Officials didn’t plan for the hotter summers and dryer winters that climate change are said to be responsible for.

  Reservoirs are low. Restriction of 50 litres per person per day.

  Have been efforts to create new desalination plants as well as new water wells but most are only half way built.
• Aral sea

   

  In 1960s soviet union undertook water diversion project to floor arid plains of Kazakhstan in order to create cotton farms which helped create wealth for the local areas but diverted the rivers away from their destination the Aral sea.
• Water table: the upper level of an underground surface in which the soil or rocks are permanently saturated with water.
• Two types of aquifer recharge: 

  Natural recharge: precipitation, riverbed seepage, flooding and other forms of natural water that enter the groundwater system.

  Artificial recharge: enhancement of natural groundwater supplies through human intervention such as infiltration basins, field flooding, infiltration galleries or injection wells.
• ‘Water abstraction’ refers to the process of taking or extracting water from a natural source (rivers, lakes, groundwater aquifers, etc.) for various uses, from drinking to irrigation, treatment, and industrial applications. ​
•  

  Confining bed: impermeable rock that lays below a aquifer allowing it to collect and not seep lower.

  Confined aquifer: thick deposits over the aquifer confine it from the earth’s surface or other rocks.
• Unconfined aquifer: where rock is directly open at the surface of the ground and groundwater is 

  directly recharged.
• Aquifers are the second largest freshwater store (30% of all freshwater) and is accessible unlike cryosphere (69%).

  Soil/ geology naturally filters the water which means less purification is required once abstracted.
• Natural recharge.

  Reducing urban sprawl, reducing flood plain development, managed deforestation, managing the water courses. (all allowing natural infiltration through changes in land use)