What is it and why is it important?

Adapted from: “Groundwater Interactive” The Kesab Watercare Club http://www.cwmb.sa.gov.au/kwc/interactive/groundwater/index.htm

Click on any number for an explanation

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

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

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

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

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

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

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

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

8. The Water Cycle

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

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

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

12. Groundwater Salinity

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

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.

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.

15. Wetlands

• Nature’s filter