Forest Hydrology

1. Canopy ForestHydrology What is the connection between forests and the water cycle? Roots Forest Floor

2. Combines aspects of two separate disciplines: • 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.

3. 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 • 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

5. Fluxes of Water Atmosphere Oceans/Continents Over land Earth surface Ground Within the Ground Ground Vegetation Vegetation Atmosphere Soils, rivers, lakes Atmosphere Precipitation Sheet flow/Stream Flow Infiltration Groundwater Flow Root Uptake Transpiration Evaporation How does water move in the hydrological cycle?

6. Stocks of Water: where does water reside on earth? Ice Caps: 69 % Groundwater: 30% Surface Water and Vegetation: 1% Oceans: 97% Earth: 3% Atmosphere: 0.001% Natural water reservoirs or storage areas

7. Photograph by Medford Taylor Photograph by Medford Taylor Shenandoah Valley Forest

8. Clean water dreamstime.com

9. Deforestation: Impacts on watersheds

12. Chesapeake Bay after a heavy rainstorm

13. Parts of a Tree • Canopy/Crown • Leaves • Branch • Trunk • Roots • Vascular tissue Diagram Source: http://exploringnature.org

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

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

17. 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

18. 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

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

22. http://ci.santa-rosa.ca.us/SiteCollectionImages/PWStorm_Home.jpghttp://ci.santa-rosa.ca.us/SiteCollectionImages/PWStorm_Home.jpg http://pics4.city-data.com/cpicc/cfiles22826.jpg

23. 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

25. Vascular tissue in trees Phloem & xylem

27. A Green versus a Desert Planet If 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

28. 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)

29. Canopy condensation: fog forest or cloud forest

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

31. 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)

32. Image: Percy Jimnez The Chungungo project Yield: 10,000 liters a day of water • 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

33. 100 units =119,000 km3/yr (after Chow et al., Applied Hydrology, 1988)