PG.81

Sources of water

Water on earth

All water on earth constitutes the hydrosphere

97% is stored in oceans2% in glaciers1% lakes, streams, ground water and the

atmosphere

Hydrologic Cycle

Water is in a continuous cycle powered by energy from the sun

4 processes: Evaporation Condensation Precipitation transpiration

The cycle

Water from the oceans evaporates wind carries it until it condenses into clouds precipitation occurs

Water that falls onto continents must make its way back to the ocean

Some water soaks into the ground (infiltration)

Plants absorb water from the ground and release it back in the atmosphere (transpiration)

When rate of rainfall exceeds earth’s ability to absorb it, runoff occurs

Factors that affect Runoff

Water flowing down a slope is runoffVegetation- more of it less run offRate of precipitation heavy rains, more

runoffSoil composition more organic material,

more porous; bigger particles, more porous = less runoff

Slope larger the slope more runoff

Streams

Land area whose water drains into a stream system is call a watershed

Ability to erode depends on gradient, shape, size, and roughness of the channel

Can measure discharge (volume that flows over a particular location in a certain amount of time)

Discharge= volume of water flowing past a certain point in a given amount of time

Lakes

Lakes can come from: Meandering streams that cut off a portion Glaciers that carve depressions Dammed streams from landslides

Eutrophication is the process by which lakes become rich in nutrients from the surrounding watershed

Wetlands

Land that is covered with water for most of the year

Includes bogs, marshes, and swampsBogs:

Receive water from precipitation Include peat moss that contributes to soil acidity

Marshes: Form along the mouth of streams with extensive deltas Lots of grass and wildlife

Swamps: Low lying areas by streams Marshes grow and become swamps

Groundwater

Most freshwater is in glaciers rest in groundwaterZone of aeration- area above water table where soil

is not saturatedZone of saturation- where groundwater completely

fills all poresUpper boundary of zone of saturations water

tableGround water flows through permeable layers

called aquifers

Erosion and deposition by groundwater

Caves are formed when limestone dissolvesSink holes are formed when caves collapse or

dissolution of bedrockRegions that have abundant sinkholes are

said to have karst topography

Ground water deposits

Water that has high concentrations of Ca, Mg, or Fe is called hard water

Dripstone formations in caves are formed from water depositsEventually form stalactites (hang from cave’s ceiling like

icicles)Water drips off stalactites to form stalagmites

Ground water systems

Springs- natural discharges of ground water Hot springs-temps higher than the human body Geysers- explosive hot springs

Wells- holes dug or drilled to reach ground water Artesian well- well that has enough pressure to spurt

out water

Threats to our water system

OveruseSubsidence- the sinking of land due to ground

water depletionPollution

Industrial waste Landfills Agricultural chemicals Chemicals – salt and radon

Pg. 82

Create a diagram of the water table and include the following words or events: The energy source Precipitation Condensation Evaporation Transpiration Zone of saturation/zone of aeration Ground water Run off Ocean Stream Lake Water table Aquifer