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