Upload
selma
View
25
Download
0
Tags:
Embed Size (px)
DESCRIPTION
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. - PowerPoint PPT Presentation
Citation preview
Water Resources
Lecture 9Degradation of the Water Resource
Sources of degradation
• Urbanisation• Alien invasion• Industrialisation• Afforestation• Agriculture• Unsustainable rangeland farming
Alien invasives: additional info
Woody alien incremental water use: 1900 m3 /year
Commercial plantation incremental use: 930 m3 /year
Dye et al, 2001
Total streamflow reduction by Alien Invasives Versveld et al
1988
Industrialisation
• Types of industry affecting water resources:– Mining – Energy– Chemical – Metal and non-metal manufacture– Waste treatment
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.
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
Other impacts by industry
• Thermal pollution – Eg cooling towers of coal power stations
Afforestation
Pine species – reduced streamflow
Afforestation in Maclear, EC:Effect on MAR
Forsythe et al, 1997
Afforestation in Maclear: Effect on low flow
Forsythe et al, 1997
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)
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
Agriculture
Agriculture• Tilling
– Increased removal of topsoil– Crusting– Reduced infiltration– Donga erosion
• Fertilizers• Pesticides
Agriculture
• Irrigation• Dumping• Draining of wetlands• Invasion by alien vegetation• Feedlot pollution
PoorRangeland Farming
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