Environmental Degradation of Water Resources: Urbanization, Industrialization, and Agriculture

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

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

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

14. 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)

17. 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

18. Agriculture

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

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

37. PoorRangeland Farming

41. 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