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Water Resources

Water Resources. Lecture 9 Degradation of the Water Resource. Sources of degradation. Urbanisation Alien invasion Industrialisation Afforestation Agriculture Unsustainable rangeland farming. Alien invasives: additional info. Dye et al, 2001.

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Water Resources

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  1. Water Resources Lecture 9 Degradation of the Water Resource

  2. Sources of degradation • Urbanisation • Alien invasion • Industrialisation • Afforestation • Agriculture • Unsustainable rangeland farming

  3. Alien invasives: additional info Dye et al, 2001 Woody alien incremental water use: 1900 m3 /year Commercial plantation incremental use: 930 m3 /year

  4. Total streamflow reduction by Alien Invasives Versveld et al 1988

  5. Industrialisation • Types of industry affecting water resources: • Mining • Energy • Chemical • Metal and non-metal manufacture • Waste treatment

  6. Mining • Release of toxins into freshwater systems: • over 1 million tons/y of effluent containing cyanide and other poisons is generated by gold-mining • the mining industry is directly responsible for 100% of highly toxic, 78% of toxic, and 66% of slightly toxic pollutants entering South Africa's water. • Climate change • coal mines contribute 35% of the 2.25 million tons of the methane which South Africa emits into the atmosphere every year • Acid rain • coal dump fires are responsible for 5.24% of the 1.95 million tons of sulphur dioxide released per year.

  7. Mining • Acidification • Headwater of Olifants: pH = 2.9 • Water demand • Mining accounts for 2.5% of SA’s water demand • Wetland degradation • Open cast mining • Dumping on wetlands • Increased salinity • Pumping of high salinity groundwater into surface water systems • Increased turbidity

  8. Other impacts by industry • Thermal pollution • Eg cooling towers of coal power stations

  9. Afforestation

  10. Pine species – reduced streamflow

  11. Afforestation in Maclear, EC:Effect on MAR Forsythe et al, 1997

  12. Afforestation in Maclear: Effect on low flow Forsythe et al, 1997

  13. Afforestation: Statistics for SA • 1.44 million hectares • Water use: 1 399 milion m3 /year • 3.2% MAR • 10% change in cover of pines/eucalypts = 40mm change in water yield (Bosch and Hewlett, 1982)

  14. Afforestation • Pines and Eucalypts have high rates of evaporation – leads to stream flow reduction • Planting often occurs in the high moisture areas of a catchment • Planting often occurs in wetlands or in riparian zones. • Reduced biotic diversity • Reduced pH • Impacts of logging and hauling

  15. Agriculture

  16. Agriculture • Tilling • Increased removal of topsoil • Crusting • Reduced infiltration • Donga erosion • Fertilizers • Pesticides

  17. Agriculture • Irrigation • Dumping • Draining of wetlands • Invasion by alien vegetation • Feedlot pollution

  18. PoorRangeland Farming

  19. Poor Rangeland Farming Practices • Overgrazing • Reduced vegetation cover • Reduced infiltration • Increased rill and gully erosion • Increased susceptibility to alien vegetation invasion • Destruction of the riparian habitat • Destruction of wetlands • High frequency fires

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