ATS2545 Lecture Notes - Lecture 11: Sea Level Rise, Porosity, Aquifer
25 May 2018
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Lecture 11 – Groundwater in Australia
Forms of Porosity in Aquifers
• Primary porosity
o The original Intergranular porosity of a conducting material
o Turns into secondary porosity as rock dissolves
• Secondary porosity
o Weathering may alter primary value by enlarging pore spaces
o May reach very high values in soluble rocks: e.g. lime stones
• Highly fractured rocks are quite permeable
The Importance of Groundwater
• #1
o Majority of freshwater (99%) is in ground water / ice
o Slow motion beneath land areas of globe
o Sea level change changes ∆H
▪ High ground water flow when sea level is low
• When sea level is low, ∆H increases
▪ Low ground water flow when sea level is high
• #2
o 80% of land area of Australia depends on groundwater
▪ Irrigation, stock
o More than 4,700 bores tap the water supply for Alice Springs
o In china, >60% of urban water is sourced from groundwater
▪ Northern China has seen a watertable drop of 70m in the last 10
years
• #3
o Groundwater flow is very slow, take up great depths beneath surface
o Flow speeds are measured in m per year
o Water becomes warm in deep aquifers as well as saline
o Groundwater plays a major role in concentrating minerals (uranium
deposits)
• #4
o Clearing of land → deforestation
▪ Increases groundwater flow
▪ Since groundwater is so high, saline seeps → salinity
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