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Forest/Land Use Hydrology

Forest/Land Use Hydrology. 7 Lectures and Tutorials 3 Pracs Topics Forestry - Internationally and in SA Forestry and Water Use in SA Interception Processes Evapotranspiration Modelling Forest Hydrology Forestry and Water Quality…….? Working for Water Case Studies PRAC

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Forest/Land Use Hydrology

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  1. Forest/Land Use Hydrology • 7 Lectures and Tutorials • 3 Pracs • Topics • Forestry - Internationally and in SA • Forestry and Water Use in SA • Interception Processes • Evapotranspiration • Modelling Forest Hydrology • Forestry and Water Quality…….? • Working for Water • Case Studies • PRAC • Modelling influences of commercial afforrestation with ACRU • Calculating Streamflow Reduction • Fieldtrip • Recommended Reading • http://www.beeh.unp.ac.za/hydro/

  2. Forest Hydrology • Hydrology • The circulation of water from the atmosphere, through the earths terrestrial and aquatic systems and back to the atmosphere is the unifying theme for the study of hydrology • Forest Hydrology • Forest hydrology is the study of forests and their unique relationship to water in forested landscapes • The overall focus of forest hydrology is on how forest vegetation and their associated soils; along with catchment topography, and climate all interact to govern the cycling of water through the forest and further downstream. • Focus is on understanding how different forest vegetation types, stand conditions influence the hydrologic cycle in catchments where afforestation has occurred. • Much of this research deals with evapotranspiration dynamics (interception of precipitation by forest vegetation, evaporation from vegetation, soil and free water surfaces, and transpiration by vegetation); and it's relationship with streamflow.

  3. Plantation Statistics

  4. Forestry • Differences between “Old Growth Forests” and commercial timber plantations • Commercial afforestation essentially a crop with a longer than normal rotation • Fast-wood plantations - intensively managed commercial plantations, set in blocks of a single species, which produce industrial round wood at high growth rates (mean annual increment of no less than 15m3 per hectare) and which are harvested in less than 20 years (Cossalter and Pye-Smith, 2003). • “Old Growth” issues usually revolve around “sustainable yield”

  5. Forestry • Hardwood • Hard to saw • Dicotyledonous • Softwood • Easy to saw • Coniferous • But much inconsistency of use and overlap

  6. Background • In South Africa, concerns for the protection of water resources have led to the control of commercial afforestation and forestry practices. • Commercial forestry is a “stream flow reduction activity” (SFRA) and as such must be licensed as one of several forms of water use. • A stream flow reduction activity is defined as • “… any activity (including the cultivation of any particular crop or other vegetation) … [that] … is likely to reduce the availability of water in a watercourse to the Reserve, to meet international obligations, or to other water users significantly” (NWA Section 36(2)).

  7. Pine – most commonly pinus Patula

  8. Black Wattle – Acacia Mearnsii

  9. Gum Trees – Most commonly Eucalyptus Grandis

  10. Latest SA Forestry figures (from Forest SA)

  11. Influences of Forestry • Increase precipitation at regional scale? • Decrease runoff? • Water quality issues • Ecological (Biodiversity) issues

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