Method 9100: Saturated Hydraulic Conductivity, Saturated ...
Groundwater Hydraulic Gradient Groundwater Pore spaces Joints/fractures Water Table Recharge...
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Transcript of Groundwater Hydraulic Gradient Groundwater Pore spaces Joints/fractures Water Table Recharge...
Groundwater
Hydraulic Gradient
Groundwater
• Pore spaces
• Joints/fractures
Water Table
Recharge
Saturated zone
Aquifers
Impermeable rock
Groundwater
Pore spaces unsaturated
Pore spaces saturated
What rocks in the UK make good aquifers?
Sandstone40% porosity
30% specific yield
High permeability
Clay
45% porosity
3% specific yield
Low permeability
Impacts of pumping water from aquifers
Impacts of pumping water from aquifers
Drawdown
Hydraulic Gradient
Cone of Depression
Impacts of pumping water from aquifers
Saline wedge
Control – reduce/stop abstraction, change pattern of abstraction ( winter not summer) or move borehole
Monitoring – chemical testing (boreholes/salinity testing)
Agriculture
• Nitrates
• Pesticides
Industry
• Chemical leaks
• Chemical spills
• Contamination from chemical storage
Waste Disposal
• Leachates from landfill sites
• Radioactive waste
Contamination of aquifers
Contamination of aquifers
Chloride content (milligrams per litre) of leachate
Monitoring
• chemical testing of water from boreholes, springs, extraction wells• ground penetrating radar (remote sensing methods)
• electrical resistivity analysis (oil pollutants = high resistivity)
• soil gas chemical monitoring (organic pollutants give off a vapour such as methane)
borehole
Most expensive
Cheapest
Contamination of aquifers
1. Control
• clay liner
• synthetic liner
• leachate collection
total containment
Contamination of aquifers
2. Control
• build barriers to plume
• trenches filled with concrete
• hammered piles injected with cement grout
Barrier to predicted depth of pollution
Pollution localised
10 – 20m max
Contamination of aquifers
3. Control
• pump pollutant to surface for treatment/disposal
Contamination of aquifers
4. Control
• direct polluted groundwater into to bioreactive barrier
• bioreactive barrier use naturally occurring bacteria to breakdown the pollutant
• oxygen & nitrates injected into barrier to encourage decay processes
factory
pollutant
Impermeable wall to direct groundwater
Bioreactive filter
Key Terminology:
1.Aquifer2.Confined aquifer3.Groundwater4.Water table5.Porosity6.Permeability7.Specific yield8.Hydraulic gradient9.Recharge10.Cone of depression11.Drawdown12.Contamination plume13.Ground penetrating radar14.Electrical resistivity15.Soil-gas monitoring16.Bioreactive barrier