1. Cycles of the Earth & Biogeochemical Cycles Hydrological Cycle
Slides 15-38

2. Environmental Systems and Biogeochemical Cycles Part 1

3. Environmental Systems and Biogeochemical Cycles Part 2

4. Water’ Unique Properties
There are strong forces of attraction between molecules of water.
Water exists as a liquid over a wide temperature range.
Liquid water changes temperature slowly.
It takes a large amount of energy for water to evaporate.
Liquid water can dissolve a variety of compounds.
Water expands when it freezes.

5. Evaporation, transpiration, condensation, precipitation
Water cycle:
Evaporation, transpiration, condensation, precipitation

6. Water cycle:

7. Hydrologic Cycle

8. The hydrologic cycle Water is essential for biochemical reactions
It is involved in nearly every environmental system
Hydrologic cycle = summarizes how liquid, gaseous and solid water flows through the environment
Oceans are the main reservoir

9. Evaporation = water moves from aquatic and land systems into the atmosphere
Transpiration = release of water vapor by plants
Precipitation, runoff, and surface water = water returns to Earth as rain or snow and flows into streams, oceans, etc.

10. Water Cycle Defined: Movement of water through the atmosphere
75% of the earth is water
99% of water undrinkable (salty & frozen)
Water recycles over and over

11. How does water rise? transpiration evaporation
Water rises into the atmosphere in two ways:
Evaporation: Heat changes water from a liquid to a gas
Transpiration: Water evaporates from the leaves of plants through openings called stomata
How does water rise?
transpiration
evaporation

12. Water in the atmosphere
Warm, moist air rises and eventually cools
Condensation: process where water vapor turns into a liquid

13. What goes up….Must come down
Precipitation: Rain, snow, sleet, or hail falls when water drops become heavy
precipitation

18. Water on the Ground transpiration evaporation
Runoff: Water runs down hill into rivers, lakes, streams, oceans…
Infiltration: Water soaks into the soil and collects as groundwater
Process repeats
transpiration
RUNOFF
evaporation
INFILTRATION

19. Groundwater
Aquifers = underground reservoirs of sponge-like regions of rock and soil that hold…
Groundwater = water found underground beneath layers of soil
Water table = the upper limit of groundwater in an aquifer
Water may be ancient (thousands of years old)
Groundwater becomes exposed to the air where the water table reaches the surface
Exposed water runs off to the ocean or evaporates

20. Condensation Transpiration Evaporation Precipitation Precipitation
Rain clouds
Transpiration
Evaporation
Precipitation to land
Transpiration from plants
Precipitation
Precipitation
Evaporation from land
Evaporation from ocean
Surface runoff (rapid)
Runoff
Precipitation to ocean
Infiltration and Percolation
Surface runoff (rapid)
Figure 3.26
Natural capital: simplified model of the hydrologic cycle.
Groundwater movement (slow)
Ocean storage
Fig. 3-26, p. 72

21. Effects of Human Activities on Water Cycle
We alter the water cycle by:
Withdrawing large amounts of freshwater.
Clearing vegetation and eroding soils.
Polluting surface and underground water.
Contributing to climate change.

22. Hydrological Cycle

23. Hydrological Cycle (water cycle)
1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land
2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water
3. Release – plants transpire, animals breathe and expel liquid wastes

24. Hydrological Cycle
1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land.
2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water.
3. Release – plants transpire, animals breathe and expel liquid wastes.

25. The Water Cycle