Canopy

Forest Floor

Roots

•Hydrology is the study of the movement, distribution, and quality of water throughout Earth, and thus addresses both the hydrologic cycle and water resources. (http://en.wikipedia.org/wiki/Hydrology)

•Forestry is the science that seeks to understand the nature of forests and the interactions among the parts comprising the forest.

Combines aspects of two separate disciplines:

•Interactive system: A set of reservoirs (water storage in oceans, lakes, soil, atmosphere, ice caps) & fluxes (precipitation, evaporation, river flow) with Water changing among three different states: gaseous, liquid, solid

www.noaa.gov

•Dynamic system: Driven by solar energy and gravity

•Closed system/cycle: water quantities constant

•Recycling system: Global-scale circulation of water through atmosphere, land, oceans

Fluxes of Water

Atmosphere Oceans/Continents Over land Earth surface Ground Within the Ground Ground Vegetation Vegetation Atmosphere Soils, rivers, lakes Atmosphere

How does water move in the hydrological cycle?

Precipitation

Sheet flow/Stream Flow

Infiltration

Groundwater Flow

Root Uptake

Transpiration

Evaporation

Stocks of Water: where does water reside on earth?

Oceans: 97%

Earth: 3%

Atmosphere: 0.001%

Ice Caps: 69 %

Groundwater: 30%

Surface Water and Vegetation: 1%

Natural water reservoirs or storage areas

Photograph by Medford Taylor

Photograph by Medford Taylor

Shenandoah Valley Forest

dreamstime.com

Clean water

Deforestation: Impacts on watersheds

Chesapeake Bay after a heavy rainstorm

Parts of a Tree

Canopy/CrownLeavesBranchTrunkRootsVascular tissue

Diagram Source: http://exploringnature.org

Source: http://www.mcelroy.ca/bushlog/images/10a-6039.jpg

http://gardening.savvy-cafe.com/wp-content/uploads/2008/06/forest-floor-1.jpg

Rainsplash

Effect of the impact of water drop on the soil surface: detachment of soil particles

After deforestation we lose the sheltering effect of canopy and forest floor. The soil surface is more exposed to rainsplash. Source:

www.montcalm.org/planningeduc0042.asp

Rainwash/Sheet Erosion

The soil particles detached by rain splashing are washed away & transported downhill by overland flow.

These soil particles eventually reach the streams increase in turbidity, sediment loads in streams and rivers

Deterioration of water quality, loss of stream habitat for fish and other organisms

Silting of lakes and reservoirs: the sediment is deposited in lakes & reservoirs loss in water storage capacity of reservoirs, which are filled with sediments

Source: www.montcalm.org/planningeduc0042.asp

http://namibsands.files.wordpress.com/2009/07/newlands_forest_roots.jpg

http://ci.santa-rosa.ca.us/SiteCollectionImages/PWStorm_Home.jpg

http://pics4.city-data.com/cpicc/cfiles22826.jpg

Summary: Forests Contribution to the Water Cycle

Effect amount of water reaching the ground (throughfall) Forests favor infiltration & reduce runoff & stream flow

Effect evapotranspiration Effect precipitation More rainfall, more

evapotranspiration more intense regional water cycle

Less soil erosion & suspended sediments better water quality

Vascular tissue in trees

Phloem & xylem

A Green versus a Desert PlanetIf we compare these two endpoints:

Green planet: all non-glaciated land covered by trees

Desert Planet: all of the planet with no vegetation

Forest vegetation causes

• intensification of the water cycle over land:

• more evapotranspiration more atmospheric moisture more precipitation

• Runoff decreases in the presence of forest vegetation because of the higher soil water holding capacity and higher evapotranspiration

Studies on Amazonian deforestation:The replacement of the forest with pasture results in a warmer and drier climate

Other effects of forests on the water cycle:Canopy condensation

Plant canopies provide surfaces suitable for condensation In regions where humid air (low clouds/fog) move through

relatively cold canopies, vegetation may “strip” atmospheric moisture off of the clouds/fog.

The condensed water drips down to the ground providing a potentially important input of water in these ecosystems

Regions affected by canopy condensation: Frequent presence of fog/low clouds, Close to the ocean, with forest vegetation

(M. Scholl, U.S. Geological Survey)

Canopy condensation: fog forest or cloud forest

Kaho`olawe: dust storms in Hawai`i Forest canopy removed

Can we make an artificial canopy to trap water?

Chungungo: small village in the Atacama desert (Chile). Experiment using polypropylene nets as “fog trappers”

A view of Chunchungo (BBC)

Image: Percy Jimnez

• First collectors erected in 1987 • Fog collectors provide more than 40 liters of water per person per day (only 14 liters/person/day were available before the project)• Project is run by the community• Similar projects in Peru, South Africa, the Dominican Republic, Israel, Cape Verde, the Canary Islands and Nepal

The Chungungo projectYield: 10,000 liters a day of water

(after Chow et al., Applied Hydrology, 1988)

100 units =119,000 km3/yr