Group 2 : Eight Legged Freaks’

Global water resources and use

The Water Resources of

Earth

Over 70% of our Earth's surface is covered by water ( we should really call our planet "Ocean" instead of "Earth"). Although water is

seemingly abundant, the real issue is the amount of fresh water available. 

97.5% of all water on Earth is salt water, leaving only 2.5% as fresh water 

Nearly 70% of that fresh water is frozen in the icecaps of Antarctica and Greenland; most of the remainder is present as soil moisture, or lies in deep underground aquifers as groundwater not accessible to human use. 

< 1% of the world's fresh water (~0.007% of all water on earth) is accessible for direct human uses. This is the water found in lakes, rivers, reservoirs and

those underground sources that are shallow enough to be tapped at an affordable cost. Only this amount is regularly renewed by rain and snowfall,

and is therefore available on a sustainable basis.

* Water as a Resource

Since antiquity, irrigation, drainage, and impoundment have been the three types of water control having a major impact on landscapes and

water flows. Since the dawn of irrigated agriculture at least 5000 years ago, controlling water to grow crops has been the primary motivation for human alteration of freshwater supplies. Today, principal demands for

fresh water are for irrigation, household and municipal water use, and industrial uses. Most supplies come

from surface runoff, although mining of "fossil water" from underground aquifers is an important source in

some areas. The pattern of water withdrawal over the past 300 years shows the dramatic increases in this

century.

●12,000 yrs. ago: hunter-gatherers continually return to fertile river valleys 

● 7,000 yrs. ago: water shortages spur humans to invent irrigation 

● 1,100 yrs ago: collapse of Mayan civilization due to drought 

● Mid 1800's: fecal contamination of surface water causes severe health problems (typhoid, cholera) in some major North American cities, notably Chicago

● 1858: "Year of the Great Stink" in London, due to sewage and wastes in Thames 

● Late 1800s-early 1900: Dams became popular as a water management tool 

● 1900s: The green revolution strengthens human dependency on irrigation for agriculture 

● World War II: water quality impacted by industrial and agricultural chemicals 

● 1972: Clean Water Act passed; humans recognize need to protect water

* A timeline of human water use:

*FRESHWATER

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, icebergs, bogs, ponds, lakes, rivers and streams, and underground as groundwater inaquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludesseawater and brackish water although it does include mineral-rich waters such as chalybeate springs. The term "sweet water" has been used to describe fresh water in contrast to salt water.

According to WIKIPEDIA

* Freshwater is defined as having a low salt concentration — usually less

than 1%. Plants and animals in freshwater regions are adjusted to

the low salt content and would not be able to survive in areas of high salt

concentration (i.e., ocean).

According to http://www.ucmp.berkeley.edu/exhibits/biomes/freshwater.php

* Earth seen from Apollo 17 — the Antarctic ice sheet at the bottom of the photograph contains 61% of the fresh water, or 1.7% of the total water, on Earth.

Runoff that occur on surfaces before reaching a channel is also called a nonpoint source.

* Surface runoff is the water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle, and the primary agent in water erosion.

* If a nonpoint source contains

man-made contaminants,

the runoff is called 

nonpoint source pollution.

*  A land area which produces runoff that drains to a common point is called

a drainage basin.

* A land area which

produces runoff

draining to a

common point

is called a watershed.

*Groundwater

Groundwater is water located

beneath the earth's surface in soil pore spaces and in the 

fractures of rock formations. –

wikipedia

Groundwater is by far the most

abundant and readily available source

of freshwater, followed by lakes,

reservoirs, rivers and wetlands:

• Groundwater represents over

90% of the world's readily available freshwater

resource (Boswinkel, 2000). About

1.5 billion people depend upon

groundwater for their drinking

water supply (WRI, UNEP, UNDP, World Bank, 1998).

• The amount of groundwater

withdrawn annually is roughly

estimated at ~600-700 km3

, representing about 20% of global water withdrawals

(WMO, 1997). • A comprehensive picture

of the quantity of groundwater

withdrawn and consumed annually around the world

does not exist.

An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology.

* A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water.

* Freshwater biomes are subdivided into three groups: lakes and ponds, streams and

rivers, and wetlands.

The freshwater biome is made up of any of body of water that is made of freshwater such as lakes, ponds, streams, and rivers. They cover roughly 20% of the Earth and are in various locations spread out all over the world. Most freshwater biomes consist of moving water and contain many types of fish.

 lake is a body of relatively still water of considerable size, localized in a basin, that is surrounded by land apart from a river, stream, or other form of moving

water that serves to feed or drain the lake.

A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake

A stream is a body of water with a current, confined within a bed and stream banks.

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a 

sea, or another river.

A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem

. Primarily, the factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation that is adapted to its unique soil

conditions: Wetlands consist primarily of hydric soil, which supports aquatic plants.

*Saltwater

*Salt water (or salt-water or saltwater) most often means the water from the seas and 

oceans. This type of water is also called sea water.

Saline water, water containing salt.

Brackish water, water that is saltier than fresh water, but not as salty as seawater.

Seawater, water from oceans or seas and ocean.

Saline (medicine), a solution of sodium chloride in sterile water.

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity

 of about 3.5% (35 g/L, or 599 mM).

Seawater is denser than both fresh water and pure water because the dissolved salts add mass without contributing significantly to the volume. The freezing point of seawater

decreases as salt concentration increases.  The coldest seawater ever recorded (in a liquid state) was in 2010, in a

stream under an Antarctic glacier, and measured−2.6 °C (27.3 °F).

* REFERENCEhttp://www.globalchange.umich.edu/globalchange2/current/lectures/freshwater_supply/freshwater.html

http://www.ucmp.berkeley.edu/exhibits/biomes/freshwater.php

http://en.wikipedia.org/wiki/Fresh_waterhttps://

en.wikipedia.org/wiki/Surface_runoff#cite_note-3http://www.softschools.com/facts/biomes/freshwater_biome_facts/166

/http://www.unep.org/training/programmes/Instructor%20Version/Part_2/Activities/Economics_of_Ecosystems/Water/Supplemental/Global_Water_Resources.pdf