Topic 8:Water and Climate
The Water Cycle
• Climate – the conditions of the atmosphere over long periods of time
• Water cycle – the movement and phase changes at and near Earth’s surface Fueled by insolation and gravity Also known as the hydrologic cycle.
The Water Cycle
• 97% of Earth’s water is held in oceans
• About 80% of Earth’s fresh water is in glaciers
• Graph of pg 160 in book
The Water Cycle
• Four places that precipitation goes if it lands on land: Water retention: water is held on land as
ice or snow or on leaves of trees and plants
Infiltration: soaks into ground Runoff: flows over Earth’s surface Evapotranspiration: water evaporates,
sublimates or transpirates back into atmosphere Most precipitation returns to
atmosphere
Condensation and sublimation(cloud formation)
Precipitation
SublimationTranspiration
Runoff
Zone of aeration
Water table
Zone of saturation
Bedrock = impermeable
Evaporation
Infiltration
Factors Affecting Infiltration
• 7 Factors affecting infiltration: Slope of the land Degree of saturation Porosity Permeability Capillarity Vegetation Land use
Slope
• What effect does slope of the land have on infiltration Steeper slope = less infiltration
slope
Infilt
rati
on
Degree of Saturation
• What effect does degree of saturation have on infiltration?
The more saturated the ground = less infiltration
saturation
Infilt
rati
on
Vocabulary• Zone of aeration – pores of soil
partly filled with air and partly filled with water (capillary water)
• Zone of saturation – pores of soil are filled with water
• Water table – interface between zone of aeration and zone of saturation
• Groundwater – subsurface water below the water table
Porosity
• Porosity – percent of open pore space in a material compared to its total volume
• What effect does porosity have on infiltration? The greater the porosity the greater
the infiltration
Porosity
• Effect of the particle characteristics on porosity: Shape: round particles = high
porosity angular particles = low
porosity Packing: loose = high porosity
packed = low porosity Sorting: sorted = high porosity unsorted = low porosity Size: DOES NOT AFFECT POROSITY
Permeability
• Permeability – how easily water passes through a material Permeability rate – how fast water
passes through a material
• Two factors that affect permeability How well connected pores are Size of pores
Permeability
• What effect does permeability have on infiltration? The more permeable the ground is
the more water will infiltrate The more permeable the faster water
will infiltrate (less time)
Capillarity
• Capillarity – the “stickiness” of water to ground particles
• Why is capillary action important? It brings water to the roots of plants
• What is the effect of particle size on capillarity? Smaller particles = greater capillarity
= more capillary water
Vegitation
• What is the effect of vegetation on infiltration? More vegetation = more infiltration
less runoff Less vegetation = less infiltration
more runoff
Land Use
• What is the effect of land use on infiltration? Urbanization decreases infiltration
More paved surfaces (roads, parking lots, buildings)
More runoff
Runoff
• What are the situations that can lead to runoff? Rate of precipitation is greater than
rate of infiltration (permeability rate) Pore space if saturated Slope is too steep to allow infiltration Water on surface has not evaporated
Stream Discharge
• Stream discharge – the amount of water flowing past a spot in a certain amount of time m3/s or L/s
Flooding
• Flooding is the result of: When a stream overflows its channel When precipitation is greater than
infiltration A hurricane storm surge Rising sea Sinking land
Climate
Climate
• Climate – the conditions of the atmosphere over long periods of time
Temperature and Moisture
• Two important factors concerning temperature and climate: Average temperature throughout the
year Range of monthly average
temperatures
Evapotranspiration
• Potential evapotranspiration – amount of water that would evapotranspirate if water was available Determined by temperature
(available energy)
Arid Climates
• An arid (dry)climate occurs when total precipitation is less than potential evapotranspiration Atmosphere can evaporate more
water than is falling
Humid Climates
• A humid (moist) climate occurs when precipitation is more than potential evapotransipiration Atmosphere is trying to evaporate
less than is falling
Factors affecting Climate
• 8 Factors affecting climate Latitude Planetary wind and pressure belts Oceans and large bodies of water Mountains Elevation Cloud cover Vegetation
Latitude
• How are latitude and temperature related? Higher latitude = lower temperatures
(yearly)
Latitude and Moisture
• What causes moisture conditions to vary with latitude? Planetary wind and pressure belts
Lows = humid climates Highs = deserts, arid climates
Latitude and Moisture
• At what latitudes are there moist conditions? Why? 0o, 30 – 60o (mid latitudes) Low pressure – rising air cools =
precipitation
Latitude and Moisture
• At what latitudes are there arid conditions? Why? Poles, 30oN, 30oS High pressure – sinking air
warms(compression) = lower RH