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Lecture 3

Earth Science 2WW3-Lecture 3 notes- Freshwater Resources & The Environment.pdf


Department
Earth Sciences
Course Code
EARTHSC 2WW3
Professor
Luc Bernier
Lecture
3

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Freshwater Resources & The Environment
Part 1 - Landscape and Water Resources
There are close natural links between landscape and water resources
Water that condenses contributing to cloud formation reaches the ground in the form of
precipitation and returns to the atmosphere through transpiration and evaporation
Water that has reached the ground can infiltrate, percolate and be reabsorbed by plants
The water will also lead to the formation of groundwater and a water table
Rocks and soils will be saturated with water and eventually water that flows as
groundwater will form springs as the water connects with the topography
The surface runoff will eventually lead to the ocean
Precipitation contributes to the formation of groundwater
The groundwater saturates rocks and soil and eventually flows to springs and eventually
the ocean
Habitat Destruction and Water
The global international water's assessment report has studied these linkages between
landscape and water
The destruction of habitats is involved in 18% of the cases of regions facing water related
issues
For 75% of the population facing water related issues pollution is involved
The absence of Cyprus swamps destroyed by logging and saltwater intrusions by man-
made canals is among the factors that lead to the flooding of New Orleans (2005)
following hurricane Katrina
Engineering of the landscape
Intensive deforestation results in major problems
Large scale irrigation results in major problems
Agriculture results in major problems

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Freshwater Resources & The Environment
Indicators of Ecosystem Health
The impact of these changes can be tracked by indicators of ecosystem health
For freshwater systems fish are good indicators because they are acclimated and in sync
with this environment
There are problems with using fish
Overfishing
Another factor in the destruction of aquatic habitat
River engineering focused on flood prevention removes shallow backwaters where fish
may breed or hide from predators
Blue and Green Waters
Water resource management has focused on rainfall and runoff of blue water because of
its potential commercial value
Evapotranspiration is considered a loss even though this is the life blood of crops and
terrestrial plants
Green water is directly used by the biosphere
It is a direct important for agriculture and economy
The FAO has adapted this dichotomy between blue and green water when discussing
water related issues
Blue Water
Baseflow:
o Fair weather flow in rivers
Baseflow is one of the forms of blue water
It takes into account groundwater seepage and river flow
It accounts for 11% of the fate of annual precipitation
Stormflow:
o Flow in rivers from rain events
Stormflow is the other form of blue water
It accounts for the fate of 27% of annual precipitation
1.5% of all blue water is used for irrigation but only half goes back to rivers
Green Water
Green water is considered lost as water vapor but now it is incorporated into concepts of
virtual water and water footprints
The majority of water supplied to crops is green water
Crops use 4% of global precipitation
Forests account for 17% of global precipitation
Grasslands account for 31% of the fate of total global precipitation
While 2/3 of human withdrawals are for irrigated agriculture this is relatively limited
compared to the fate of natural watering

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Freshwater Resources & The Environment
Part 2 - Agriculture and Water Resources
Irrigation and Dissolved Salts
Because of the presence of dissolved salts in freshwater irrigation may be a source of
major problems in arid areas and also an ancient one
o E.g. Iraq
Farm culture is now being lost to salinization in Iraq
It is also a problem near the Aswan high dam where irrigated land is also being lost
It is also a problem in the Aral Sea Basin where it has been impacted by years of
unsustainable diversion of water away from the sea to irrigation in land
Indicators of Salinity
Electrical Conductivity:
o Indicates general level of dissolved substances in water
Elevated levels are seen in Mexico, Middle East and North America due to problems with
the Colorado River due to unsustainable irrigation
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