Water Resources

1. Water Resources Mrs. Ashley

2. Water as a Resource • Earth’s surface – 70% water • 97% of water in oceans: salt water • 3% is fresh water • 25% of fresh water is groundwater • 75% of fresh water is in ice and glaciers • Only .03% of water is available to us: in atmosphere, streams, rivers, wetlands, lakes • (Some is lost to pollution)

3. Properties of Water • Polar Covalent Bond (sharing of electrons) • Polarized due to – side and + side • Water Molecules become bonded weakly with positive to negative sides of different water molecules (hydrogen bonds) • High Specific heat • Specific 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 Earth • Stores tremendous quantities of heat energy with small rise in temperature

4. Properties of Water

5. High Specific Heat Energy • Water 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 fall • The 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

6. Properties of Water • Known 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

7. Properties of Water • pH 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 together • Allows water spiders and water striders to walk on water • Slows down mayflies and caddisflies when they try to emerge from water

8. Adaptation of Mayfly Larvae • The 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.

9. Properties of Water • Viscosity is the force necessary to separate the molecules and allow an object to pass through • Water’s frictional resistance is 100 times greater than air • Organisms in water need a streamlined body to pass through the water

10. Properties of Water • Adhesion: Water adheres to and climbs up materials like glass • The 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

11. 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)

12. Water and Oxygen • 21 % of air is oxygen • Only 1% of water is oxygen • More oxygen tends to be at surface of water • Wind action • Photosynthesis • Waves • Benthic organisms tend to use up oxygen (BOD)

13. 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 float • Trapped air is also effective in helping to float • Waterfowl float high in the water due to air trapped in their feathers and the hollow bones in their skeletons

14. 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

15. Oceans

16. Salinity measured in psu

17. Acidity in Oceans • Carbon dioxide in water • Forms Carbonic Acid H2CO3 H2O +CO2 • H2CO3 H + CO3 Hydrogen and Carbonate • Below a pH of 4.5 organisms cannot grow and reproduce

18. Ocean Currents • Winds drive currents • Higher temperature less dense so floats on top • Thermocline-layer where temperature changes rapidly • Thermal stratification is permanent in tropics • Temperate regions stratification is only in summer and fall has turn over which results in nutrient mixing

19. Ocean Currents

20. Ocean Currents • Gyres • Move right in northern hemisphere and left in southern hemisphere • Surface and deep water currents • Upwelling on western side of continents and Anartica

21. Lake Zonation • Divisions 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

22. Lake Zonation