Groundwater Water Table Recharge Saturated zone Groundwater Hydraulic

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

Aquifers Pore spaces unsaturated Groundwater Pore spaces saturated Impermeable rock

What rocks in the UK make good aquifers? Sandstone 40% 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 Cone of Depression Hydraulic Gradient Drawdown

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)

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

Contamination of aquifers borehole 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) Most expensive Cheapest

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

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

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

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

Key Terminology: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 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