Hydrologic Cycle & Forest Hydrology Notes & Answers

Candace Lutzow-Felling for Blandy Bay Academy 2012

SLIDE 1TITLE SLIDE.

Learning goal: to understand the role of trees and forests in the water cycle

Water: essence of life

Availability determines where and how animals and plants exist on Earth

SLIDE 2. FOREST HYDROLOGY

Hydroecology: study of the interface between the hydrologic cycle and life sciences; plant-water interactions; ecohydrology

Influence is bi-directional; involves feedback mechanisms; trees influence the water cycle & the water cycle influences trees

Forest hydrology: a sub-field of ecohydrology; how trees influence the hydrologic cycle in forest ecosystems

Hydrology is an interdisciplinary science that includes

  • Chemistry: chemical properties of water and interactions with the environment (including the biota)
  • Physics: movement of water through the hydrologic cycle (gravity and E absorption and transfer)
  • Geology: water storage; water movement; soil dynamics
  • Environmental Science/Ecology: interactions with biotic and abiotic components
  • Biology: intake, use and outflow of water from organisms

SLIDE 3. HYDROLOGIC CYCLE

Hydrologic cycle synonym = ___water cycle______

Hydrologic cycle definition: __the process by which water moves through the Earth’s atmosphere, land surface (including rivers, lakes, and groundwater), oceans, and subsurface______

What is the source of energy and the main force that drives the hydrologic cycle?

Energy __solar______Force__gravity______

What does FLUX mean? _change in water from one area to another______

SLIDE 4. GLOBAL WATER BUDGET

Water budget is a tool to quantify the water cycle; the rates of movement and change in water storage in all or parts of the atmosphere, land surface, and subsurface.

What is the MAIN important factor to understand about the global water budget?

The total amount of water is constant.

Is there more precipitation over land or over the ocean? ocean

What is the ratio of precipitation over land to ocean? 1:>3

Why do you think there is more precipitation over the ocean than the land?

more ocean area on the earth/more water evaporating over the ocean

Water from the land to the ocean flows from these twosourcesland surface & rivers & groundwater

Which source has the greater quantity of flow into the ocean? land surface

Does precipitation over land equal evaporation from the land?NO

If this land P/E cycle continues, what would happen to the land water budget? There would be a net deficit.

What keeps the land water budget in balance? Evaporation from the ocean; this water is moved over the land by air currents (advection).

SLIDE 5. FLUXES OF WATER

How does water move in the hydrologic cycle (what are the processes)?

How does water move from the atmosphere to the land? precipitation

How does water move from the land or body of water to the atmosphere?evaporation

from the ground to vegetation root uptake

from vegetation to the atmospheretranspiration/evaporation

from land to oceanrivers/groundwater/run-off

from ocean to landevaporation & advection

from earth’s surface to below groundinfiltration/percolation

from below ground to vegetationuptake

within the groundgroundwater flow

overlandstream flow/sheet flow

This movement of water from one portion of the hydrologic cycle to another is called flux.

SLIDE 6. WHERE DOES WATER RESIDE ON EARTH?

All water of Earth resides in three compartments of the hydrologic cycle:

Diagram 1. Paolo D`Odorico, ecohydrologist, water compartments or apportionment

Diagram 2. USGS water compartments or apportionment: atmosphere, hydrosphere, lithosphere

Where is water stored on Earth? What are the NATURAL reservoirs or water storage areas? For each water reservoir, what is the main phase of water that is stored?

1.lakes & ponds(liquid)5. rivers(liquid)

2. ocean (liquid6. plants & animals & microbes (biota)(liquid)

3.ground water:aquifers(liquid)7. soil (liquid)

4.atmosphere(gas)8.glaciers (ice)

Where do we find water stored as ice? oceans (arctic ice) & land (glaciers)

SLIDES 7-12. FORESTS & DEFORESTATION IMPACTS

Example illustrating the hydrologic connection between upland forests and the ocean

Why are forests so important when studying the hydrologic cycle?

  1. Forests occupy about 1/3 of the earth’s land area
  2. Tree leaves account for >2/3 of the leaf area of land plants; therefore, play a very important role in terrestrial hydrology

SLIDE 13.PARTS OF A TREE

What are the main parts of a tree involved in the cycling of water?

1.crown2. leaves 3. roots

4. branches5. trunk 6. vascular tissue

SLIDE 14. FOREST CANOPY

How does the forest canopy interact with the water cycle?

1. intercepts precipitation 2. promotes condensation

3.changes drop size & reduces velocity

SLIDE 15. LEAF LITTER

Why is leaf litter important to the hydrologic cycle?

1.increases infiltration

2.slows overland flow

(also traps sediments & sequesters nutrients)

SLIDE 16. DEFORESTATION IMPACTS

What are the major consequences of removing the forest canopy?

1. rain drops are not intercepted 2. erosion

SLIDE 17. RAIN SPLASH

What can happen during a precipitation event when the canopy & leaf litter is removed?

rain drop velocity is not decreased, rain quantity is not reduced (from interception), & soil particles can become detached

SLIDE 18. EROSION

Rain splash over a large area can have these impacts downstream in a watershed:

  1. sedimentation (turbidity)
  2. siltation (sediment deposited in lakes & rivers)
  3. water quality decreases
  4. water storage capacity decreases

SLIDE 19. TREE ROOTS

Three ways that roots impact the soil ecosystem are:

1. stabilize the soil components & stream banks

2. increase infiltration

3.draw water from deep in the soil

SLIDES 20-21. DEFORESTATION: Impacts on watersheds.

Cutting or removing trees from an ecosystem can result in this series of events during a heavy rainstorm:

1. increase water flow 2.increase erosion 3increase sedimentation

Example of large-scale slope erosion after a heavy rainfall.

Propose a landslide risk management strategy for this mountainous region.

SUMMARY

Why are forests so important when studying the hydrologic cycle?

1. SCALE. Forest occupy about 1/3 of the earth's land area.

2. LEAVES. Tree leaves account for > 2/3 of the leaf area of land plants; therefore, they play a very important role in terrestrial hydrology. Leaves also can impact local humidity levels.

3. ROOTS. Extensive root systems stabilize soil. They affect water movement in soil through the capillary process.

4. VASCULAR SYSTEM. This system creates a soil-plant-atmosphere continuum moving large amounts of water from the soil though the plant and into the atmosphere.

5. CANOPY. Intercepts precipitation

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