1. Groundwater Water Table Recharge Groundwater Hydraulic Gradient
Saturated zone
Groundwater
Hydraulic Gradient
Pore spaces
Joints/fractures

2. Aquifers Groundwater Impermeable rock Pore spaces unsaturated
Pore spaces saturated

3. What rocks in the UK make good aquifers?
Sandstone
40% porosity
30% specific yield
High permeability
Clay
45% porosity
3% specific yield
Low permeability

4. Impacts of pumping water from aquifers

5. Impacts of pumping water from aquifers
Cone of Depression
Drawdown
Hydraulic Gradient

6. 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)

7. Contamination of aquifers
Industry
Chemical leaks
Chemical spills
Contamination from chemical storage
Waste Disposal
Leachates from landfill sites
Radioactive waste
Agriculture
Nitrates
Pesticides

8. Contamination of aquifers
borehole
Chloride content (milligrams per litre) of leachate
Monitoring
Most expensive
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)
Cheapest

9. Contamination of aquifers
1. Control
clay liner
synthetic liner
leachate collection
total containment

10. Contamination of aquifers
Barrier to predicted depth of pollution
10 – 20m max
2. Control
Pollution localised
build barriers to plume
trenches filled with concrete
hammered piles injected with cement grout

11. Contamination of aquifers
3. Control
pump pollutant to surface for treatment/disposal

12. Contamination of aquifers
factory
pollutant
Bioreactive filter
Impermeable wall to direct groundwater
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

13. Key Terminology:
Aquifer
Confined aquifer
Groundwater
Water table
Porosity
Permeability
Specific yield
Hydraulic gradient
Recharge
Cone of depression
Drawdown
Contamination plume
Ground penetrating radar
Electrical resistivity
Soil-gas monitoring
Bioreactive barrier