Resource Hydrology: Groundwater

Front 1

Describe the Hydrological Cycle

Back 1

Front 2

Describe the water zones in the soil structure

Back 2

Front 3

Describe aquifer stratification

Back 3

Front 4

What happens when a borehole is pumped w.r.t the cone of depression?

Back 4

The cone of depression extends and deepens as pumpingcontinues, but the rate at which it deepens decreases with time

Front 5

Describe how a primary aquifer (through sand) functions

Back 5

Front 6

Describe how a secondary aquifer (through cracks) functions

Back 6

Front 7

What four methods/models are used to find possible borehole sites?

Back 7

Conceptual models

Aerial photos

Orthophotos

Geophysical models

Front 8

What are the five different geophysical models?

Back 8

Electromagnetic

Magnetic

Resistivity

Gravity

Seismic

Front 9

Describe the structure of a borehole pipe

Back 9

Front 10

What are the three main categories of pump types?

Back 10

- Variable displacement pumps

- Positive displacement pumps

- Airlift pumps

Front 11

What are the two types of variable displacement pumps?

Back 11

- Centrifugal pumps

- Jet pumps

Front 12

What are the two types of positive displacement pumps?

Back 12

- Rotary pumps

- Piston pumps

Front 13

What do pump tests in boreholes determine?

Back 13

- Sustainable yield

- Storativity and permeability

- Amount of water

- How long borehole will last

- How many boreholes are necessary

- Which pumps and how deep

Front 14

What characteristics of the environment can be determined from maps that are applicable to borehole?

Back 14

- Access roads

- Height above mean sea level

- Contour information

- Possible observation boreholes

- Property boundaries

- Possible aquifer boundaries

Front 15

Which three tests are used to measure groundwater levels?

Back 15

- Slug test

- Well performance test (step and multirate)

- Constant rate test and recover

Front 16

What are the minimum and wellfield management recommended times when estimating aquifer parameters performance the constant rate test?

Back 16

Mininum = 12 hours

Wellfield = 72 hours

Front 17

When performing the constant rate test, how does one go about determining the sustainable yield?

Back 17

1. Stress the borehole

2. De-water fractures

It should take 8 hours to reach the main water strike.

Front 18

What is monitoring?

Back 18

Meaningful measurements of a variable on a once-off basis during initial impact assessments, or on a routine basis

Front 19

Why is monitoring done?

Back 19

To comply with permits and to understand the system's behaviour in order to determine current trends and predict future trends.

Front 20

When is the specialised knowledge of a qualified geohydrologist neded?

Back 20

During the installation of a groundwater monitoring system

Front 21

How far must the monitoring network extend?

Back 21

Beyond the zone of impact from the source

Front 22

Where must future waste facilities be sited?

Back 22

On poor aquifer regions

Front 23

What are the origins of groundwater pollution?

Back 23

- Mines

- Dumping sites

- Agriculture

- Industry

- Pit latrines

- Cemeteries

Front 24

What is necessary to sustain the long term use of ground water?

Back 24

- A water balance

- Contamination is prevented

Front 25

What does 'water balance' mean?

Back 25

What that is removed must be replaced or recharged?

Front 26

Name the characteristics of aquifers that make them particularly susceptible to contamination

Back 26

- Shallow water tables

- Thin soil covers

- Coarse soils with a low clay content

- Unconfined

- Associated with a low pH water

Front 27

Why are aquifers difficult to clean up?

Back 27

- The water can't be seen, so it is difficult to define the exact extent of the pollution.

- Pollutants interact with soil and aquifer materials, so that even if the source was removed, they continue to be released from the rocks

- Groundwater is very slow moving and recharge is usually a small percentage of rainfall, thus flushing of the aquifer system can take hundreds or thousands of years.

Front 28

Describe the borehole protection zone 1

Back 28

A fence around theborehole at a proposed distance of at least 5 m and a sanitary seal

Front 29

Describe the borehole protection zone 2

Back 29

The idea is toprotect the drinking water from microbial and nitrate pollution

Front 30

Describe the borehole protection zone 3

Back 30

If persistenthazardous non-degradable elements are present, the whole catchment area of theborehole must be protected

Front 31

What is the water reserve?

Back 31

The quantity and quality of water needed:

- To satisfy basic human needs

- To protect aquatic ecosystems of the water resource

Front 32

Describe the sea water intrusion process

Back 32

Front 33

If the fresh water water table drops by 1 metre, by how much will the salt water interface rise?

Back 33

40 metres

Front 34

What is the brief concept of artificial recharge?

Back 34

Store water underground when it is available, and recover it when it is needed

Front 35

What are the four main applications and benefits of AR?

Back 35

1. Maximise natural storage

2. Water quality management

3. Physical management of aquifer

4. Ecological benefits

Front 36

What are the four water storage schemes?

Back 36

1. Seasonal storage

2. Long-term storage

3. Emergency storage

4. Diurnal storage

Front 37

How does AR help with physical management of aquifers?

Back 37

- Restore groundwater levels

- Prevent salt water intrusion

- Control contaminant plumes

Front 38

What are the ecological benefits from AR?

Back 38

- Reduce abstraction from rivers

- Maintain the reserve

- Minimise environmental imprint

Front 39

What are other benefits of AR? VIECCERS

Back 39

- Store huge volumes of water

- Rapid implementation and staged development

- Defer expansion of water facilities

- Low capital costs in comparison with dams

- Mitigate effects of climate change

- Save on evaporation

- Store reclaimed water

- Utilise saline aquifers

Front 40

What are the four main types of AR schemes?

Back 40

1. Aquifer storage and recover (ASR)

2. Aquifer storage, transfer, and recovery (ASTR)

3. Infiltration basins

4. Bank filtration

Front 41

Describe aquifer storage and recovery

Back 41

Injection and abstraction from the same borehole

Front 42

Describe aquifer storage, transfer, and recovery

Back 42

Injection and abstraction from different boreholes

Front 43

Describe infiltration basins

Back 43

Allow water to infiltrate the water table from a dam-like structure

Front 44

Describe bank filtration

Back 44

River water is induced to flow through the alluvium to wells located alongside the river

Front 45

What are the ten success criteria for AR schemes? QMELEMINSH

Back 45

1. Water quality

2. AR method and engineering issues

3. Environmental issues

4. Legal and regulatory issues

5. Economics

6. Management and technical capacity

7. Institutional arrangements

8. The need for AR

9. The source water

10. Aquifer hydraulics

Front 46

With regards to water quality as a success criteria for AR, which five characteristics of the borehole must considered beforehand?

Back 46

1. The groundwater quality

2. Blending of source water and ground water

3. Water-rock interactions

4. Clogging

5. Pre-treatment prior to AR

Front 47

With regards to engineering issues as a success criteria for AR, which three considerations must be made?

Back 47

1. Which AR method is the most efficient

2. How can the scheme be designed to minimise clogging

3. Are the engineering logistics practical

Front 48

With regards to environmental issues as a success criteria for AR, name four advantages

Back 48

1. Reduce abstraction from rivers

2. Maintain the reserve

3. When confined aquifers are used, there is very little environmental impact

4. Minimal land use as opposed to dams

Front 49

With regards to environmental issues as a success criteria for AR, name four disadvantages

Back 49

1. The water table can raise and impact the environment

2. The water table can lower and impact the environment

3. Water quality issues such as clogging and mobilisation of undesirable chemicals

4. Aquifer organisms

Front 50

What legal and regulatory issues can prohibit and AR scheme from being implemented

Back 50

AR schemes need to be licensed

Front 51

With regards to economic issues as a success criteria for AR, what must be done beforehand?

Back 51

An economic studyshould compare cost per cubic metre of water from AR and surface storagefacilities

Front 52

With regards to management and technical capacity as a success criteria for AR, what skills are needed to manage the AR scheme?

Back 52

1. Hydrogeology

2. Recharge and recovery technology

3. Groundwater level monitoring

4. Water treatment and water quality management

5. Water supply engineering

Front 53

With regards to institutional arrangements as a success criteria for AR, what are the most significant impediments to implementing a cost-effective program?

Back 53

1. Licensing

2. Monitoring

3. Water quality control

4. Financial arrangements

5. Rights to the use of recharged water

6. Reporting

7. Support

Front 54

Oftentimes, better aquifer management is needed, rather than an AR scheme. What does this aquifer management include?

Back 54

1. Decreasing the pumping rate of existing boreholes and increasing pumping hours to obtain needed volumes.

2. Monitoring the water levels in pumping and nearby non-equipped boreholes

Front 55

With regards to the need for AR as a success criteria for AR, when is AR needed?

Back 55

1. When abstraction already exceeds recharge and lateral inflows into the aquifer/wellfield

2. You plan to increase abstraction to be greater than recharge and lateral inflows

3. You want to treat water by filtering it in the aquifer

Front 56

With regards to the need for AR as a success criteria for AR, what key points must be considered beforehand?

Back 56

1. When water is ready for AR, is there enough space in the aquifer?

2. If you reduced the borehole pumping rates and increased pumping hours, would AR be necessary?

3. If you increase the aquifers volume by drawing water levels down deeper prior to AR, would there be negative environmental impacts?

Front 57

With regards to aquifer hydraulics as a success criteria for AR, what three considerations must be made beforehand?

Back 57

1. Will the recharge water be able to flow into the aquifer?

2. Will the aquifer have sufficient space to accept the water? And if so, will the pressure system be such that it accepts the water?

3. Will the water be recoverable, and for how long?