groundwater

Question 1

importance of hydrologic cycle

Answer 1

without it there would be no clouds, rivers, glaciers, oceans, groundwater, plate tectonics, rock cycle, or life on Earth

Question 2

in excavations and tunnels, what are some dangers of groundwater and solutions

Answer 2

• inflow during construction

- artificially lower water table

Question 3

aquifers

Answer 3

saturated rock/soil layers forming a reservoir for groundwater. contains pores or open spaces to hold water and these pores are generally all connected.

Question 4

4 types of aquifer

Answer 4

1. unconfined
2. confined
3. semi-confined (leaky)
4. perched

Question 5

unconfined aquifer

Answer 5

water table is exposed to the atmosphere and continuous so it is free to rise and fall

Question 6

confined aquifer

Answer 6

the groundwater is isolated from the atmosphere by less permeable layers, subject to higher than atmospheric pressure

Question 7

aquitard

Answer 7

less permeable layer than aquifer

Question 8

aquiclude

Answer 8

impermeable layer

Question 9

semi-confined aquifer

Answer 9

recharge or discharge occurs through the confining layers (aquitards)

Question 10

perched aquifer

Answer 10

water table discontinuous, exposed to atmosphere, free to rise and fall

Question 11

2 aquifer properties

Answer 11

storage and flow

Question 12

porosity

Answer 12

percentage of aquifer consisting of pore space. larger pore space = larger porosity = larger water holding capacity

Question 13

permeability

Answer 13

capacity of aquifer to transmit water through its pore spaces. related to the connectivity of pores

Question 14

2 forms of porosity

Answer 14

1. primary porosity - pores space created during aquifer formation
2. secondary porosity - pore space formed through fracturing and weathering of aquifer

Question 15

what type of porosity dominates in sedimentary rocks?

Answer 15

primary porosity

Question 16

hydraulic head (h)

Answer 16

height above a datum of a column of water that can be supported by the hydraulic pressure at a given point in an aquifer.
used to determine hydraulic gradient

Question 17

hydraulic gradient (i)

Answer 17

rate of change in hydraulic head (h) per unit distance of flow in a given direction. equates to slope of water table ro piezometric surface

Question 18

Darcy’s law (Q)

Answer 18

measures flow rate of water draining through porous material. Applies at macroscopic level

Question 19

hydraulic conductivity (k)

Answer 19

rate of flow through a unit cross-sectional area of a material under a unit hydraulic gradient (1)

Question 20

anisotropic

Answer 20

k varies with direction

Question 21

isotropic

Answer 21

k is the same in all directions

Question 22

homogenous

Answer 22

k is the same in all positions

Question 23

heterogenous

Answer 23

k is different in different positions

Question 24

are aquifers heterogenous or homogenous?

Answer 24

heterogenous

Question 25

easy or hard to quantify anistropy and heterogenity in aquifer

Answer 25

hard because of the high degrees

Question 26

groundwater is full of particle mater and polluted with sea water and NO3….
TRUE/FALSE

Answer 26

true apart from particles filtered out as it flows through the ground

Question 27

some dangerous pollutants in groundwater

Answer 27

• Fe and Mn ions, from rocks , encrusts pipes and favours bacterial growth
• NO3- too much is toxic to babies and cattle.
• faeces from sewage leak

Question 28

cone of depression

Answer 28

as groundwater is extracted, flow is induced towards well. The velocity and pressure increases towards the well and thus cone forms, centred on the well. Decreases pressure away from the well which can lead to settlement.