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Groundwater

Groundwater. What is it and why is it important?. Click on any number for an explanation. Adapted from: “Groundwater Interactive” The Kesab Watercare Club http://www.cwmb.sa.gov.au/kwc/interactive/groundwater/index.htm. 1. What is Groundwater?. Water that runs below the earth’s surface

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Groundwater

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  1. Groundwater What is it and why is it important? Click on any number for an explanation Adapted from: “Groundwater Interactive” The Kesab Watercare Club http://www.cwmb.sa.gov.au/kwc/interactive/groundwater/index.htm

  2. 1. What is Groundwater? • Water that runs below the earth’s surface • Water found in most water bodies such as lakes, rivers, streams and wetlands is known as surface water

  3. 2. Aquifer • If it weren’t for aquifers we’d be wading in water up to our waists • Water runs off into streams, lakes, ponds and aquifers • Aquifers are underground reservoirs • Water that enters aquifers • Usually is much cleaner than surface water • Contains almost no bacteria • Many pollutants are filtered out • Two types of Aquifers: confined and unconfined

  4. 3. Confined Aquifer • An aquifer below the surface that is saturated with water • Contains layers of impermeable material both above and below • These layers cause the water to be under pressure • If penetrated by a well the water will rise above the top of the aquifer

  5. 4. Unconfined Aquifer • Allows water to enter freely from above and below • Closer (generally) to the surface than confined aquifers • Impacted by drought conditions sooner than confined aquifers

  6. 5. Porosity & Permeability (1) • The amount of water that can be stored in an aquifer depends on two factors: • Porosity: refers to the amount of pore spaces or fractures in an aquifer • Porous aquifers consist mainly of loose gravel, sands and silts • Water fills any space between the gravel, sand and silt

  7. 6. Porosity & Permeability (2) • Permeability • Refers to the rate of infiltration • Sandy soils allow quick infiltration of rainfall • Clay soils quickly saturate and surface flow removes most of the rainfall • Only all small portion reaches groundwater • Impermeable rock would not allow water to enter

  8. 7. Groundwater Wells • Groundwater is obtained by drilling a well into an aquifer • A casing or pipe is placed inside the well to stop the wall from falling inward • The space between the casing and rough wall is filled with concrete to prevent leaking • Well screen at the bottom is used to filter out sand and gravel

  9. 7. Groundwater Wells (cont’d) • Once this is done a pump is inserted into the well • A well can become contaminated if not properly constructed • Two types of wells • Artesian: Comes from a confined aquifer • Unconfined : comes from an unconfined aquifer

  10. 8. The Water Cycle

  11. 9. Groundwater Use • Groundwater • Industry uses: beer, soft drinks, spring water, pulp and paper. Etc • May be used as the sole water supply for stock and domestic purposes • Requires minimal treatment

  12. 10. Threats to Groundwater • Groundwater is usually of excellent quality • Since it is naturally filterer it is usually clear colorless, and free from microbial contamination • A threat to groundwater is now posed by a number of soluble chemicals from urban, industrial and agricultural activities • These chemicals can not be completely removed by the natural filtration process

  13. 11. Groundwater Contamination • Many of the pollutants of surface water also contaminate groundwater • Surface pollutants can move through the soil and find their way into aquifers • Examples are: • Pesticides • Fertilizers • Motor oil • Gasoline • Untreated waste

  14. 12. Groundwater Salinity • The most common cause is the replacement of perennial, deep-rooted native plants with crops and grasses

  15. 13. Saltwater Intrusion • The key to controlling this problem is to maintain the proper balance between water being pumped from the aquifer and the amount of water recharging it.

  16. 14. Threats to Quantity • Overdraft occurs when groundwater is removed faster than recharge can replace it. This can result in; • A permanent loss of some of its storage capacity. • Contamination of clean water with low quality water. • Drawdown A temporarily lowered water table generally caused by pumping. • The water table only recovers when the supply is replenished. • Subsidence • Is one of the dramatic results of over pumping. • As the water table declines, water pressure is reduced. • This causes the fine particles that hold water to become compacted. • In addition to permanently reducing storage capacity, the land above the aquifer can dramatically be effected causing it to sink. • This can damage property and fields.

  17. 15. Wetlands • Nature’s filter

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