Lecture 15

Question 1

Phases of water

Answer 1

• liquid water
• ice
• water vapour

Transitions between phases absorb and release energy (latent heat of melting and vaporization)

Absorb energy going from more ordered to less ordered phase

Question 2

Properties of ice

Answer 2

• unusual mineral
• polar character
• open crystal lattice
• lower density than liquid form
• water expands as it freezes

Consequences:

• ice floats
• expansion of freezing water fractures rocks

Question 3

Properties of liquid water

Answer 3

• excellent solvent for ionic and polar substances
• a small portion of water molecules are dissociated into H+ and OH-
• H+ actually attached to near by water molecule to make a hydronium molecule
• high surface tension as a result of polarity and H bonding

Question 4

pH

Answer 4

The -log[H+]

Ocean is slightly alkaline whereas surface waters are quite acidic

Question 5

Hydrologic pathways

Answer 5

• condensation/precipitation
• evaporation and transpiration
• infiltration and subsurface flow

Question 6

Hydrologic reservoirs

Answer 6

• oceans (97.5%)
• ice sheets (2%)
• groundwater (0.64%)
• lakes, rivers, atmosphere (0.01%)

Question 7

Largest reservoir of fresh water?

Answer 7

Polar ice sheets

Question 8

Largest reservoir of unfrozen fresh water?

Answer 8

Groundwater

Question 9

Hydrologic pathways

Answer 9

Condensation:

• water vapour to liquid or solid
• falls as precipitation (rain or snow)

Evaporation:
-from sea or land

Transpiration:
-from plants

Surface flow:

• glaciers (melting)
• rivers and streams

Subsurface flow:
-infiltrations (groundwater movement)

Question 10

Hydrologic budget

Answer 10

Fluxes:

Greatest for atmosphere then ocean then land

Overall closed system

Question 11

Groundwater

Answer 11

• groundwater flow
• water in the lithosphere
• solution and mineral precipitation from groundwater
• free water in pore spaces within the solid Earth
• less then 1% of earth’s water
• exact amount uncertain, especially at depth

Question 12

Porosity

Answer 12

• the amount of empty space (pores) in a sediment or rock
• expressed as % by volume
• can be filled with air, water, oil, natural gas..

Question 13

Permeability

Answer 13

-measure of the ease through which fluid can flow through a rock

Depends on:

• porosity
• size of pore spaces
• connectedness

Question 14

Zones of groundwater

Answer 14

Zones of aeration: pores partly filled with water

Zones of saturation: pore spaces entirely filled

Water table: the surface separating these zones

Question 15

Form of the water table

Answer 15

• water table typically rises under hills
• generally a subdued imitation of shape of landscape
• rises and falls with variations in rainfall and discharge of water

Question 16

What drives groundwater flow?

Answer 16

• groundwater flows from regions of high pressure to regions of low pressure
• at a given depth, pressure is higher if water table is higher
• hydraulic head measures pressure difference driving flow

Question 17

Recharge and discharge areas

Answer 17

Recharge: water passes from surface into groundwater system

Discharge: water exits from groundwater system into surface water