Therese CamilleriSt. Michael School Scout Group
The Water Cycle
Therese Camilleri VSLSt. Michael School Scout Group
Therese Camilleri VSLSt. Michael School Scout Group
Therese Camilleri VSLSt. Michael School Scout Group
The Role of Water for Living Organisms
Without water, the other nutrient cycles would not exist in their present forms and current forms on earth would not exist.
Water determines the type of organisms in terrestrial systems.
Therese Camilleri VSLSt. Michael School Scout Group
The Role of Water for Living Organisms
The flow of water in an out of an aquatic ecosystem affects physical conditions for organisms by influencing temperature, salinity, and availability of nutrients.
Therese Camilleri VSLSt. Michael School Scout Group
How the Water is Cycled in the Ecosphere
Main process of the water cycleEvaporationTranspirationCondensationPrecipitationInfiltrationPercolationRunoff
Therese Camilleri VSLSt. Michael School Scout Group
Evaporation
Conversion of water into air vapor
Therese Camilleri VSLSt. Michael School Scout Group
Evaporation Cont
Water cycle is powered by energy from the sun and gravity.
Solar energy evaporates water from oceans, streams, lakes, soil, and vegetation.
Therese Camilleri VSLSt. Michael School Scout Group
Evaporation Cont
Percent of water vapor in atm. includes84% from oceans16% from land
Amount of water vapor entering the atmosphere is amount of water returning to earths surface.
Therese Camilleri VSLSt. Michael School Scout Group
Transpiration
Evaporate from leaves of water, extracted from soil by roots, and transported through the plant.
Therese Camilleri VSLSt. Michael School Scout Group
CondensationConversion of water vapor
into droplets of liquid water.
Therese Camilleri VSLSt. Michael School Scout Group
Precipitation
Rain, sleet, hail, and snow.
Therese Camilleri VSLSt. Michael School Scout Group
Water VaporAmount of water vapor air can hold
depends on temperature.Warm air is capable of holding more
water vapor than cold air.
Therese Camilleri VSLSt. Michael School Scout Group
Humidity
Absolute HumidityAmount of water vapor found in a
certain mass of air.Usually expressed as grams of water
per kilogram of air.
Therese Camilleri VSLSt. Michael School Scout Group
Humidity Cont
Relative HumidityThe amount of water vapor in a
certain mass of air.Expressed as a percentage of the
maximum amount it could hold at that temperature.
Therese Camilleri VSLSt. Michael School Scout Group
Example of Relative Humidity
Example: Relative humidity of 60% at 27 degrees Celsius means that each kg of air contains 60% of the maximum amount of water vapor it could hold at that temperature.
Therese Camilleri VSLSt. Michael School Scout Group
InfiltrationThe movement of water
into soil
Therese Camilleri VSLSt. Michael School Scout Group
PercolationDownward flow of water
through soil and permeable rock formations to groundwater storage areas called aquifers.
Therese Camilleri VSLSt. Michael School Scout Group
RunoffDownslope surface
movement back to the sea to resume the cycle.
Therese Camilleri VSLSt. Michael School Scout Group
Water Vapor to Precipitation
Winds and air masses transport water vapor over earth’s surfaces.
This water vapor condenses into tiny droplets that form clouds as a result of falling temperatures.
Therese Camilleri VSLSt. Michael School Scout Group
Water Vapor to Precipitation Cont
Precipitation will then occur only if the air has condensation
For condensation to occur the temperature must be at dew point.
Therese Camilleri VSLSt. Michael School Scout Group
Precipitation to Runoff77% of precipitation falls to the sea,
the rest falls to land.Some of the precipitation becomes
locked in glaciers
Therese Camilleri VSLSt. Michael School Scout Group
Precipitation to Runoff cont
Most of the precipitation becomes surface runoff flowing into streams and lakes which eventually carry water back to the oceans where it starts all over again.
Therese Camilleri VSLSt. Michael School Scout Group
Surface RunoffReplenishes streams and lakes.Causes soil erosion.Water dissolves many nutrient
compounds which makes it a major medium for transporting nutrients.
Therese Camilleri VSLSt. Michael School Scout Group
PercolationSome of the water returning to the land
soaks into (infiltrates) the soil and porous rock and then percolates downward, dissolving minerals from porous rocks on the way.
This water is stored as groundwater in the pores and cracks of rocks.
Therese Camilleri VSLSt. Michael School Scout Group
Percolation ContWhere the pores are joined, a network of water
to flow through the porous rock.Aquifer: water-laden rockWater table: level of the earth’s land crust to
which it is filled.
Therese Camilleri VSLSt. Michael School Scout Group
Percolation Cont
This underground water flows slowly downhill through rock pores and seeps out into streams and lakes or comes out in springs.
This water evaporates or reaches the sea to continue the cycle.
Therese Camilleri VSLSt. Michael School Scout Group
Humans Influence the Water Cycle
Humans intervene in the water cycle in three main ways: We withdraw large quantities of fresh
water.We clear vegetation from land.We modify water quality
Therese Camilleri VSLSt. Michael School Scout Group
Humans Influence the Water Cycle cont
We withdraw large quantities of fresh water from streams, lakes, and underground sources. This has led to depletion or
intrusion of ocean salt water into underground water supplies
Therese Camilleri VSLSt. Michael School Scout Group
Humans Influence the Water Cycle cont
We clear vegetation from land for agriculture, mining, road and building construction and other activities. This increases runoff and reduces
infiltration that recharges groundwater supplies.
Increases the risk of flooding and accelerates soil erosion and landslides.
Therese Camilleri VSLSt. Michael School Scout Group
Therese Camilleri VSLSt. Michael School Scout Group
Bibliography http://www.learner.org/exhibits/weather/watercycle.html http://www.epa.gov/OGWDW/kids/cycle.html
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Watercycle.shtml
http://www.sensorland.com/HowPage037.html http://www.ph-measurement.co.uk/home.htm http://sjr.state.fl.us/programs/outreach/conservation/landscape/images/
phbarp6.jpg http://old.jccc.net/~pdecell/chemistry/phscale.html http://www.epa.gov/airmarkets/acidrain/ph.html http://www.css.cornell.edu/faculty/hmv1/watrshed/CDIB354.gif http://www.nwd-wc.usace.army.mil/nwp/gifs/pics/transpiration.gif http://www.dutchstandard.com/droplet.gif Miller, G. Tyler Jr. Living in the Environment. Pacific Grove; Brooks/Cole
Publishing Company, 2000.
Top Related