Water

Fresh WaterTwo types of standing bodies of water:

◦Lakes◦Wetlands

Lakes are formed when a depression in the ground fills with water◦Water can come from rivers, springs,

rain, melting snow, or surface runoff◦Lakes have 4 zones: littoral, limnetic,

profundal, benthic

LakesLittoral is the shallow

zone located at the top of a lake and exposed to sunlight; Life forms include crustaceans and amphibians

Limnetic zone is in the middle of the lake; life forms include plankton and predators

LakesProfundal is the deeper

zone that received little sunlight; life forms include detritivores

Benthic is the layer of sediment at the bottom of a lake; life forms include insects and tiny crustaceans

WetlandsWetlands are land that is saturated

with water2 types: marshes and swamps

◦Marshes form as sediment accumulates at the bottom of a lake and oxygen runs out which leads to grassy vegetation taking over

◦In contrast swamps have a woody vegetation

WetlandsWetlands are important for several

reasons◦Protect the land from flooding◦Recycle nutrients into the soil◦Purify water by removing pollutants◦Provide shelter for animals◦Home to unique carnivorous plants

and rare reptiles and amphibians

RiversRivers are an important source of fresh

water, containing less than 1% dissolved salts◦Rivers begin at headwaters, with sources

including springs, lake, or runoff◦As the water flows downhill it speeds up

(greater gradient), picks up sediment (speed dependent) , and water

◦The bottom of the river wears away as the rocks move along

◦Rivers end at the mouth at another body of water

RiversYoung rivers typically have a fast

movement speed, can carry large rocks, have few tributaries or meanders

Mature rivers move slower, can carry smaller rocks, have many tributaries, and no meanders

Old rivers move slow, can only carry sand and mud, have fewer tributaries, and many meanders

RiversYoung stream

Mature stream

Old stream

http://www.dkimages.com/discover/previews/774/206778.JPG

Moderate Slope

Steep Slope

Gentle Slope

Stages ofStream/River Development

Oxbow Lake

Oxbow Lake

FloodingFlooding has both positive and

negative consequences◦Flooding deposits fertile soil in a

delta and a flood plain◦Deltas are alluvial deposits at the

mouth of the river, deposited as the water slows down

◦Flood plains are flat land next to the river that becomes covered with water during a flood; when the river floods silt, sand, or gravel is left behind

FloodingFloods can also cause serious damage

(Hurricane Katrina)◦Levees are barriers along riverbanks

that prevent water from overflowing (natural or manmade)

◦Sandbags are bags dropped continually to repair breaches (water getting through)

◦Dams are huge walls that stand in the way of rising waters

WatershedA watershed is an area of land from

which water flows into a river, stream, lake or ocean◦Vary in size, Mississippi River

watershed covers 40% of the USPollution in a watershed can affect all

organisms in the watershed◦Non-point pollution from farms,

urban runoff, and other sources◦Point source pollution (factories) can

pollute entire watersheds

Underground waterUnderground water reserves are

located around the world and are vital to life on Earth◦Seeps into porous soil or rocks

underground◦Gravity moves water and

replenished by water cycle◦Provides drinking water to ½ world

population and important for agriculture and industry

Underground waterZone of aeration is the underground

layer that contains empty spaces and spaces filled with water (relatively dry)

Water table is boundary between the zone of aeration and the zone of saturation; minimum depth to drill to receive reliable supply of water

Zone of saturation is the underground layer which all pores are filled with water (lowest)

Impermeable rock is underground layer that has no empty spaces

Underground water

Ground waterInfiltration is the movement of water

from the ground surface into the soil◦Soil properties affect infiltration:

porosity, permeability◦Gravity◦Capillary action is the movement of

water in porous areas (can fight gravity)

Underground waterAquifers is a body of saturated rock

through which water can easily move, must have layers of permeable and impermeable rock◦Unconfined aquifer’s upper boundary

is the water table, less protected and easily polluted

◦Confined (artesian) aquifer are sandwiched between two impermeable layers, more protected and less likely to be polluted

Underground waterUnderground water can surface in several ways

◦Artesian spring: water flows sideways and bursts through the surface

◦Artesian well (confined aquifer): drilling into aquifer causes water to come to surface (no pump) due to pressure

◦Geyser: water is heated underground and bursts through the surface

◦Man-made well: water is pumped above ground

◦Hot spring: spring whose water is heated underground by molten rock

Oceans

Ocean WavesWind energy is transferred through

friction and creates waves on the ocean’s surface◦As waves come ashore the ground

slows it down and causes it to topple over itself

◦Erodes structures including cliffs, notches, sea caves, sea arches, sea stacks

Ocean WavesParts:

◦Crest: top of the wave◦Trough: lowest point between two crests◦Wave period: time it takes for two

consecutive crests to pass a fixed point◦Wave height: distance between the

trough and crest◦Wavelength: distance from one crest to

the next◦Wave base: half the wavelength

Parts of a Wave

Ocean TidesTides are caused by gravity from the

pull of the sun and moon on Earth◦Spring tides are the highest and

lowest tides which occur during a full moon or new moon (sun and moon are aligned)

◦Neap tides are the smallest tides which occur during the first and last moon quarters (sun and moon are not aligned)

Ocean CurrentsOcean currents are caused by

different temperatures and densities◦Surface currents result from the

effects of the wind◦Deep currents are caused by

temperature and density differences◦The currents generally move by cold

water travelling from the Poles to the equator; warm water travels from the equator to the Poles

Ocean CurrentsThe Coriolis Effect prevents water and

air from travelling in a straight line◦Deflected by the motion of the

Earth’s rotation

OceansWater at the equator is typically warm

and has a lower densityWater at the poles is typically cold and

has a higher density

Sea Level ChangeMany are concerned that global

warming could cause the sea level to rise◦Temperatures increase due to global

warming◦Glaciers melt◦Sea level rises due to increase in

ocean volume◦Erosion and flooding

Currents and WeatherChanges in oceanic and atmospheric

currents can have drastic effects on the weather

Normal conditions◦Western Pacific is typically very

warm and rainy because easterly trade winds bring warmth and push water toward the west; pressure is lower

◦Eastern Pacific is typically cooler air because winds blowing away warmth; pressure is higher

Normal Conditions

El Nino/ Southern OscillationThe wind-driven movement of warm water in

the Pacific shifts, causing extreme disruptions to weather systems around the globe◦Western, tropical Pacific has higher air

pressure, and eastern Pacific is lower◦Trade winds are weakened and causes them to

blow backwards (west to east)◦Eastern Pacific is warmer and receives more

rain, western Pacific is cooler and drier; eastern Pacific has less nutrient-rich water

◦Occurs every 3-7 years and lasts ~18 months

La NinaPressure and trade winds reverse

dramatically◦Dramatic upwelling occurs in eastern

Pacific, resulting in very cold water◦Western Pacific is wetter than normal◦Eastern Pacific is drier than normal◦Lasts 9-12 months

La Nina

http://video.nationalgeographic.com/video/el-nino

https://www.youtube.com/watch?v=IvmeUStFvz8