Water ResourcesMrs. Ashley

Water as a ResourceEarth’s surface – 70% water97% of water in oceans: salt water3% is fresh water25% of fresh water is groundwater75% of fresh water is in ice and glaciersOnly .03% of water is available to us: in

atmosphere, streams, rivers, wetlands, lakes(Some is lost to pollution)

Properties of WaterPolar Covalent Bond (sharing of electrons)Polarized due to – side and + sideWater Molecules become bonded weakly with

positive to negative sides of different water molecules (hydrogen bonds)

High Specific heatSpecific heat is the amount of heat energy it

takes to raise or lower the temperature of 1 gram of a substance by 1°Celsius

Moderates temperatures on EarthStores tremendous quantities of heat energy with

small rise in temperature

Properties of Water

High Specific Heat EnergyWater has the highest latent heat of vaporization

which means that water going from liquid to gas requires a lot of energy

Energy released or absorbed in transforming states is latent heat

Large quantities of heat energy required to change states

Waters warm slowly in spring, cool slowly in fallThe high specific heat of water, coupled with the

amount of heat absorbed or released in changing its physical state, combined with the vast quantities of water on the planet, means that water plays a major role in climate and weather

Properties of WaterKnown as a

universal solvent (substance dissolved is called solute)

Pure water becomes denser as cooled until 4 degrees Celsius and then becomes less dense

Causes ice to float

Properties of WaterpH of pure water is neutral (7)Has high surface tension (water molecules are more

attracted to each other than the air to water)-cohesion is where hydrogen bonds of water tend to keep molecules sticking togetherAllows water spiders and water striders to walk on waterSlows down mayflies and caddisflies when they try to emerge from water

Adaptation of Mayfly LarvaeThe interplay of hydrophobic and hydrophilic surfaces with water can

perhaps best be seen by examining mayflies. These organisms have aquatic larvae with hydrophilic surfaces. These

surfaces allow the larva to exchange gasses (O2, CO2) with the surrounding water, which can come very close to the hydrophilic skin.

At maturity, the larval mayfly molts to the winged subimago, the stage that must break through the water's surface. The subimago is covered with small waxy hairs and beads that are hydrophobic. The subimago floats to the surface and is literally pushed out of the water as the polar water molecules attempt to reform behind the subimago.

The subimago can float comfortably on the surface of the water for several seconds - long enough to provide a target for trout, and the basis for fly-fishing - before taking off.

It will fly to streamside vegetation and molt again; it is the only insect to molt once it has reached the winged stage. This second molt gets rid of the awkward, heavy, waxy coat of the subimago.

Properties of WaterViscosity is the force necessary to separate

the molecules and allow an object to pass throughWater’s frictional resistance is 100 times

greater than airOrganisms in water need a streamlined body to

pass through the water

Properties of WaterAdhesion: Water adheres to and climbs up

materials like glassThe qualities of adhesion and cohesion are

what allows water to rise up inside of the tall xylem tubes. This is capillarity. The narrower tubes the more capillarity

Properties of Water•The heating and cooling of the water also changes its density•High water density allows sound to move through it over long distances (important for whales)

Water and Oxygen21 % of air is oxygenOnly 1% of water is oxygenMore oxygen tends to be at surface of water

Wind actionPhotosynthesisWavesBenthic organisms tend to use up oxygen

(BOD)

Applications to Environmental Science Most organisms have bodies that are at least 75-90% water,

which means that at least 90% of their body weight will be offset by the weight of the water around them.

Benthic organisms usually deal with staying on the bottom by making that last 10% of the body as dense as possible; they may have heavy shells, massive bones, or even construct cases out of rocks to carry around

Swimming organisms (nekton), or floating organisms (plankton), have the opposite problem. They make the remaining 10% of their bodies as light as possible. Fats and oils are two biological molecules that are less dense than water and allow some organisms to float.

Sharks have large, oil-filled livers which help them floatTrapped air is also effective in helping to floatWaterfowl float high in the water due to air trapped in their

feathers and the hollow bones in their skeletons

Oceans

Divisions based on: 1. Light penetration: Photic Zone, Aphotic Zone 2. Distance from shore and depth: Neritic Zone, Oceanic Zone 3. Open water or bottom: Benthic Zone, Pelagic Zone, Abyssal Zone 4. Intertidal 5. Continental shelf 6. Hydrothermal vent

Oceans

Salinity measured in psu

Acidity in OceansCarbon dioxide in waterForms Carbonic Acid H2CO3 H2O +CO2

H2CO3 H + CO3 Hydrogen and Carbonate

Below a pH of 4.5 organisms cannot grow and reproduce

Ocean CurrentsWinds drive currentsHigher temperature less dense so floats on

topThermocline-layer where temperature

changes rapidlyThermal stratification is permanent in tropicsTemperate regions stratification is only in

summer and fall has turn over which results in nutrient mixing

Ocean Currents

Ocean CurrentsGyres

Move right in northern hemisphere and left in southern hemisphere

Surface and deep water currentsUpwelling on western side of continents and

Anartica

Lake ZonationDivisions based on:

1. Light penetration: Photic zone, Aphotic zone 2. Distance from shore and depth: Littoral Zone, Limnetic Zone 3. Open water or bottom: Benthic Zone, Pelagic Zone

Lake Zonation