Water Cycle:
Slide 1 Earthscape
The major reservoirs for water are similar to those in the Carbon cycle.
(Slide 2)
Hydrosphere – stores water in two forms
1) liquid water stored in oceans, rivers, streams, etc.
(Slides 3 and 4 of water
distribution)
2) frozen water stored in glaciers, snow fields and polar ice caps (Cryosphere)
(Slide 5 Antarctic Ice Cap)
Lithosphere – stores and transports water in porous materials like sandstone. This is referred to
as groundwater. Groundwater is filtered as it passes through the sandstone removing
impurities and pollutants.
(Slide 6)
(Slide 7)
Biosphere – Plants and animals take in and use water for many of their life processes. A small
amount of water will be given off as a result of respiration and waste elimination. Plants release
water from their leaves in a process called transpiration.
Atmosphere – contains water mainly as vapor, droplets and ice crystals concentrated in clouds
as a result of condensation.
Water enters the atmosphere mainly by evaporation and transpiration, with a small portion
being contributed by respiration and waste elimination.
Water leaves the atmosphere mainly through precipitation.
Residence times in each reservoir. (Slide 8)
Evaporation Lab
The factors that may affect the rate of evaporation, with their effect on evaporation when
increased, include:
1) Temperature of the water
Evap. increases
2) Temperature of the Air
Evap. increases
3) Surface area
Evap. increases
4) Atmospheric pressure
Evap. decreases
5) Concentration of salt in the water Evap. decreases
6) Wind
Evap. increases
7) Humidity
Evap. Decreases
8) Motion of the Water
Evap. Increases
9) Shape of the container
No effect
10) Amt of Sunshine (changes temp of air and water)
Heat Transfer Review: What are the three ways that heat is transferred? Describe each.
Heat from the sun reaches earth via radiation. (Slide 9)
This heat causes water on the surfaces of the Hydrosphere and Lithosphere to evaporate. (S 10)
The heat causes the moisture to rise. As the moisture in the air rises it cools and condenses to
form clouds. (S 11)
This evaporated moisture will be supplemented by water being released in transpiration (S 12)
and Respiration. (S 13)
When the amount of water absorbed by the air becomes larger than the air can support the
water returns to the earth’s surface as precipitation. (S 14)
Once on the surface the water can:
Collect in open bodies of water such as lakes, rivers and oceans.
Runoff over the land until it reaches an open body of water
Seep into the ground becoming ground water (Infiltration). (S 15, 16, 17 and 18)
Eventually the water will evaporate again starting the process over.
Human activities can affect this process by altering the various reservoirs. Two of the largest
changes that we make that affect this process are covering the earth’s surface with nonporous
materials, such as pavement (Urbanization) and deforestation.
Urbanization (Slides 19 and 20)
Increasing the amount of pavement reduces the amount of water that can reach and be absorbed
by the soil.
This increases the amount of runoff and decreases the amount of infiltration. ( S 21 & 22)
Increased runoff results in more water flowing into rivers and streams during a storm
increasing stream flow and flooding. (S 23 & 24)
Increases in the rate of flow in a stream will increase the amount of erosion. (S 15)
Groundwater is long term storage for water. Since less water is being added to the ground
water, the water table moves lower reducing the amount of groundwater. (S 16) The result is
more flooding during rainy seasons and reduced water levels during dry seasons. During a
prolonged drought this may lead to wells running dry.
A secondary effect of increased runoff is increased water pollution. Groundwater is filtered as
it passes though porous rocks; less water being filtered means more pollutants remain in the
water.
Deforestation
(S 25, 26 & 27)
Trees serve a number of important functions.
1) their roots hold soils in place
2) they slow the rate of water flowing over the land allowing more time for infiltration
3) they store water
4) transpiration increases the amount of water in the air (humidity) thereby increasing local
rainfall.
Reducing the amount of tree cover will therefore:
1) reduce humidity and rainfall
2) decrease the amount of water added to the ground water
3) increase runoff and erosion.
4) Lower the water table and reduce the amount of groundwater