Global Hydrological Cycle

Flashcards covering key terms related to the Global Hydrological Cycle.

Global Hydrological cycle

Evaporation

• conversion of liquid water to water vapor

• occurs when a water molecule in a liquid has enough energy to break free of the chemical bonds within the liquid, and enter the atmosphere

  • higher temp = more energy available

Transpiration

• The process by which water vapor is released from plants into the atmosphere

• conversion of liquid water to water vapor by plants (evap through a biological linkage)

Condensation

• conversion of water vapor to liquid water

• occurs when a water molecule in the air comes into contact with a water molecule in the liquid

  • the grater number of vapor water molecules in the air, the greater change that this collision will occur

water vapor requires a physical substance to form a basis for condensation:

dust particles, chemicals produces by plants, etc. in the atmosphere “seed” the atmosphere

Precipitation

• condensation under gravitational pull

• condensed water vapor falls to Earth due to gravity as rain, snow, sleet, or hail

Sublimation

• The direct transition of water molecules from a solid state to a vapor state without becoming liquid

• movement of water molecules directly from a solid state to a vapor state

Movement of runoff

• all water that falls on land as rainfall must eventually drain into the ocean reservoir

Vapor Pressure

The pressure exerted by water vapor in the air at any given moment.

evaporation rate

• how much water is moving from a liquid state to a vapor state over time

  • depends on the temperature of the liquid

    • the warmer to liquid, the faster the rate of evap

condensation rate

• how much water is moving from a vapor to a liquid state over time

  • depends on the vapor pressure in the air directly in contact with the liquid water

Relative Humidity (RH)

• when rates of condensation and evaporation are equal

  • air is “full” of all the water vapor it can hold

  • air is saturated at 100% RH

    • at this point water will condense in the atmosphere

what are the two classes of terrestrial reservoirs

Green water and Blue water

Blue Water

• all water held temporarily in non-living reservoirs

  • lakes, rivers, ice, soil moisture, groundwater, oceans, and atmosphere

Green Water

• all water held temporarily in biological life

• Major driver of water movement on land

  • the majority of precipitation is initially taken up by plants (green water reservoir)

what is the major driver of water movement on land?

Green water reservoirs (plants that take up precipitation)

Glacier

• masses of ice and snow build up / compressed over hundreds of thousands of years

  • ice and snow persist if local temps do not rise above 0C during the year

  • lower levels of snow get compressed by the weight of upper layers of snow

    • forms solid ice under increasing pressure

Soil-water zone

• closest to the surface

• where plant roots and animal activity take place

• soil particles have lots of empty space in btw then (room for oxygen and plant roots)

• contains some water (but water is held tight to the surface of the soil particles)

Unsaturated Zone

• The zone within the soil where the spaces between soil particles are filled mainly with air

• contains very little active biological life aside from soil microbes

• where water that escapes capture by biological life is carried by gravity (deeper)

Saturated Zone

• The zone in which all voids or pores within the soil or rock are filled with water

Water Table

• The upper boundary of the saturated zone of groundwater

• boundary btw saturated and unsaturated zones

• all space below this is completely filled with water (groundwater)

Groundwater

• Water located beneath the Earth's surface, held in soil and rock formations

• Below water table

Cryosphere

Frozen water part of the Earth system, including glaciers and polar ice.

Residence Time

• The average amount of time water spends in a particular reservoir

• retention time

• if the system is in a steady state:

  • can calculate this

  • = reservoir volume / flow rate