GROUNDWATER SUPPLIES

Question 1

is the water found underground in the cracks and spaces in soil, sand and rock

Answer 1

Groundwater

Question 2

usually composed of gravel, sand, and sandstone

Answer 2

Aquifer

Question 3

allow water to pass through as they have large connected spaces that make them permeable.

Answer 3

Aquifer

Question 4

refers to the amount of water that a rock or aquifer can provide.

Answer 4

Water Yield

Question 5

It’s a measure of the quantity of water that can be extracted from the geological formations.

Answer 5

Water Yield

Question 6

Why is groundwater important as a water source?

Answer 6

*reliable during droughts and not easily depleted
*generally easier and cheaper to treat than surface water

Question 7

Prolific sources of underground water

Answer 7

*Sedimentary Rocks
*Sandstones
*Limestones
*The Chalk

Question 8

not an indicator of its ability to give a good water yield

Answer 8

Rock Porosity

Question 9

is also a determining factor for good water yield

Answer 9

Permeability

Question 10

*high porosity
*lack permeability
*limited water yield

Answer 10

Clays and Silts

Question 11

*high porosity
*prolific yielder of water *extensive network of fissures can store large quantities of water and readily release it.

Answer 11

Solid Chalk

Question 12

*yielding large quantities of water in wet weather
*drains rapidly in dry conditions *resulting in a low water yield

Answer 12

Limestone

Question 13

Formations Used for Water Supply; These are so widespread that, despite their varying yields, they form the principal source of water supply.

Answer 13

*Shallow Alluvial Strata
*Sands and Gravels of Tertiary or Recent age

Question 14

use different methods and screening techniques to access thebest quality or quantity of water regardless if they are shallow ordeep.

Answer 14

Boreholes

Question 15

has a borehole sunk from their base to intercept main water-bearing strata, sealed to prevent surface water entry.

Answer 15

Large-diameter wells (15-25 m deep)

Question 16

sometimes have adits or unlined tunnels driven below ground,intercepting more water-bearing fissures.

Answer 16

Older wells

Question 17

involves sinking several moderately sized boreholes in a spacedpattern, collecting their yields together.

Answer 17

Well field

Question 18

using porous or unjointed pipes, can abstract shallowgroundwater from river beds or banksusing

Answer 18

Collector wells and galleries

Question 19

can be driven into a hillside to tap the water table.

Answer 19

Collector wells and galleries

Question 20

rate of discharge where the
water is transferred under a
hydraulic gradient over a unit
width of an aquifer

Answer 20

Transmissivity (T)

Question 21

the amount of water released
from an aquifer when a unit fall
in the water table occurs.

Answer 21

Storage coefficient (S’)

Question 22

intrinsic characteristic of a
substance and refers to the amount
of void or empty space in each
material.

Answer 22

Porosity (n)

Question 23

Water movement through rock or
soil depends on porosity, which
relates to the

Answer 23

Hydraulic conductivity and
permeability

Question 24

a measure of how easily water can
pass through soil or rock.

Answer 24

Hydraulic conductivity and
permeability

Question 25

storage term for unconfined aquifer where the amount of water from the unconfined aquifer releases from the
storage per unit surface area of the aquifer per unit decline in the water table

Answer 25

Specific yield (Sy)

Question 26

aims to find how much water a well or borehole will presently yield

Answer 26

Test pumping

Question 27

Heavy chisel is suspended on a cable
Cable is shortened and released
alternately
Progress:
Slow
Dependent on
the hardness of
formation
Can be delayed
due to resharpening
of drill chisel

Answer 27

Cable-Operated Chisel

Question 28

Operates using compressed air
10 times faster in hard rock compared to a cable-operated chisel
Used for small boreholes (about 300 mm ⌀)
Unsuitable for soft formations & inoperable in deep depths of water

Answer 28

‘Down The Hole’ Hammer

Question 29

Used for large boreholes
More expensive than percussion drilling
May be difficult penetrating hard boulders
Has toothed cutters of hard steel that rotate and break up the formation
Used for holes of substantially smaller
diameter

Answer 29

Rotary Drilling - Roller Rock Bit