Ground Water 1

Question 1

why use GW

Answer 1

• excellent source of potable water
• largest available reservoir of fresh water
• resilient to drought

Question 2

GW uses

Answer 2

• large use in irrigation
• supplies baseflow to rivers and streams
• augment river flow in droughts

Question 3

GW characteristics

Answer 3

• areally distributed
• slow response
• low capital but high operational (pumping costs)
• lack of data thus loads of interpolation

Question 4

potential sources of GW contamination

Answer 4

• petrol/sewage leaks
• nitrates (agriculture)
• landfill

Question 5

water as a mineral

Answer 5

• anarchic behaviour
• lead to a bunch of legisation

Question 6

aquifer materials

Answer 6

principle
- chalk
- sandstone
- limestone

superficial
- glacial deposits
- river deposits
- weathering deposits

Question 7

aquifer definition

Answer 7

geological formation capable of yielding economic quantities of water through wells

Question 8

ground water resource evalation

Answer 8

Exploration
- surface/subsurface geological/geophysical data
- surface hydrological data
- hydrogeological data

Evaluation
- getting parameters
- determine yield

Exploration
- well installation
- observation well construction: well screen, gravel pack, development

aiming towards a sustainable reservoir

Question 9

well installation techniques

Answer 9

Shallow
- hand dug
- driven
- bored

Deep = drilling
- cable tool
- rotary
- reverse rotary

Question 10

getting aquifer parameter

Answer 10

• pumping test = transmissivity, storativity, specific yield
• piezometer test = permeability
• lab tests = permeability, porosity, alpha?

Question 11

evaluation: yield

Answer 11

well = max pumping without lowering the water level to below inlet

aquifer = max withdrawal with acceptable reduction in acquifer hydraulic head

catchment = same as aquifer plus no unacceptable changes to the basins hydrological cycle
- forms basis for safe yield

Question 12

sustainable yield

Answer 12

• less than annual recharge (rainfall, leakages from lakes n dat, artificial)
• doesnt lower the water table to allow intrusion of water at undesirable quality

catchment water balance
- sustainable lead to a rate of change of ground storage as zero

in general: pumping leads to reduced discharge and increased recharge

Question 13

groundwater footprinit

Answer 13

indication of how stressed an aquifer is