The Hydrologic Cycle: The Blue Planet: Chapter 8
The Hydrologic Cycle: The Blue Planet: Chapter 8
The Hydrologic Cycle: The Blue Planet: Chapter 8
• Movement of water
through the
hydrologic cycle is
powered by the Sun
• Evaporation
• Condensation
• Precipitation
• Transpiration
• Surface runoff
• Infiltration
OUTLINE
1. In three states on
Earth’s surface
2. Dipolar
a. Surface tension
b. Capillary attraction
c. Solvent
3. High heat of
vaporization and high
heat capacity
4. Solid is less dense than
liquid
5. Transparent (allow sun
light to penetrate)
WATER ON THE GROUND
• Meandering channels
• Sediment accumulates
on the inner side of a
meander, forming a
point bar
• Collapse of the stream
bank occurs on the
outside of a meander,
forming a cut bank
• In this way meanders
tend to migrate
• Sometimes a stream
bypasses a channel
loop, cutting it off and
forming an oxbow lake
WATER ON THE GROUND
• Braided channels
• A stream that is unable to transport
the entire available sediment load
tends to deposit the coarsest and
densest sediment to form a bar,
which locally divides and
concentrates the flow
• A stream with many interlacing
channels and bars is called braided
• Tends to have variable discharge and
easily erodible banks
WATER ON THE GROUND
• Less than 1% of the liquid water in the hydrosphere lies beneath the ground
• Groundwater
• It comprises a volume 35 times larger than the volume of all the freshwater lakes
and streams, and is nearly a third as large as all the glaciers and sea ice
• More than 50% of it is within 750 m depth
WATER UNDER THE GROUND
• The water table represents the upper limit of all readily usable groundwater
• It follows the shape of the ground surface, higher under hills, and lower under valleys
WATER UNDER THE GROUND
• Groundwater flows between pore spaces by percolation
• This flow depends on the porosity and permeability of the rock it moves through
• Porosity: the percentage of the total volume of rock that consists of open pore
spaces
• Permeability: a measure of how easily a solid allows fluids to pass through it
WATER UNDER THE GROUND
• Groundwater flows from high water table areas to low water table areas in
response to gravity
• Replenishment occurs when rainfall and snowmelt enter the ground in areas of
recharge
• Water moves through the system to areas of discharge, where it meets the surface,
streams, lakes, ponds or wetlands
WATER UNDER THE GROUND
• An aquifer is a body of rock or regolith sufficiently porous and permeable to store and
conduct significant quantities of groundwater
• If it has a water table, it is unconfined
• If the rate of withdrawal exceeds the rate of local groundwater flow, a cone of
depression may form
• A confined aquifer is bounded above and below by impermeable rock (aquiclude)
• If it has high hydrostatic pressure, it is an artesian aquifer, freely flowing
WATER UNDER THE GROUND
• An aquifer is a body of rock or regolith sufficiently porous and permeable to store and
conduct significant quantities of groundwater
• If it has a water table, it is unconfined
• If the rate of withdrawal exceeds the rate of local groundwater flow, a cone of
depression may form
• A confined aquifer is bounded above and below by impermeable rock (aquiclude)
• If it has high hydrostatic pressure, it is an artesian aquifer, freely flowing
WATER UNDER THE GROUND
• About 1.2 billion people, mainly In developing countries, do not have access to clean
drinking water
• In North America, water is drawn from relatively clean sources, but is still monitored
and treated with chlorination to kill microorganisms
WATER AND SOCIETY
• The accessibility of surface water makes them useful resources, but highly
susceptible to contamination
• Contaminants come from
• Urban, suburban and agricultural runoff
• Industrial and landfill effluents
• Mining, logging and petroleum discharge
• Airborne contaminants
• Thermal pollution
WATER AND SOCIETY
• A common form of surface water contamination results from excess plant
nutrients from fertilizers and detergents
• Triggers algae growth, and aquatic weeds get out of control: algal bloom
• When they die, their breakdown causes oxygen depletion, killing other organisms
in the water: eutrophication
• If accelerated by the addition of anthropogenic pollutants, it is called cultural
eutrophication
WATER AND SOCIETY