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Topic 8: Water and Climate
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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.
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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
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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
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Condensation and sublimation (cloud formation) Precipitation Sublimation Transpiration Runoff Zone of aeration Water table Zone of saturation Bedrock = impermeable Evaporation Infiltration
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Factors Affecting Infiltration 7 Factors affecting infiltration: Slope of the land Degree of saturation Porosity Permeability Capillarity Vegetation Land use
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Slope What effect does slope of the land have on infiltration Steeper slope = less infiltration slope Infiltration
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Degree of Saturation What effect does degree of saturation have on infiltration? The more saturated the ground = less infiltration saturation Infiltration
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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
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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
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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
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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
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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)
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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
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Vegitation What is the effect of vegetation on infiltration? More vegetation = more infiltration less runoff Less vegetation = less infiltration more runoff
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Land Use What is the effect of land use on infiltration? Urbanization decreases infiltration More paved surfaces (roads, parking lots, buildings) More runoff
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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
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Stream Discharge Stream discharge – the amount of water flowing past a spot in a certain amount of time m 3 /s or L/s
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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
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Climate
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Climate – the conditions of the atmosphere over long periods of time
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Temperature and Moisture Two important factors concerning temperature and climate: Average temperature throughout the year Range of monthly average temperatures
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Evapotranspiration Potential evapotranspiration – amount of water that would evapotranspirate if water was available Determined by temperature (available energy)
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Arid Climates An arid (dry)climate occurs when total precipitation is less than potential evapotranspiration Atmosphere can evaporate more water than is falling
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Humid Climates A humid (moist) climate occurs when precipitation is more than potential evapotransipiration Atmosphere is trying to evaporate less than is falling
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Factors affecting Climate 8 Factors affecting climate Latitude Planetary wind and pressure belts Oceans and large bodies of water Mountains Elevation Cloud cover Vegetation
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Latitude How are latitude and temperature related? Higher latitude = lower temperatures (yearly)
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Latitude and Moisture What causes moisture conditions to vary with latitude? Planetary wind and pressure belts Lows = humid climates Highs = deserts, arid climates
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Latitude and Moisture At what latitudes are there moist conditions? Why? 0 o, 30 – 60 o (mid latitudes) Low pressure – rising air cools = precipitation
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Latitude and Moisture At what latitudes are there arid conditions? Why? Poles, 30 o N, 30 o S High pressure – sinking air warms(compression) = lower RH
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