Aquifer Properties

Question 1

Transmissivity

Answer 1

symbol: T
Units: m2/s

A measure of the amount of water that can be transmitted horizontally through the saturated portion of the aquifer

Question 2

Can be shown mathematically as

Answer 2

T= b.K

T= transmissivity (m2/s)
b= thickness of the saturated portion of the aquifer (m)
K= hydraulic conductivity

Question 3

Storativity (storage coefficient)

Answer 3

symbol: S

the volume of water that will be absorbed or expelled from storage per unit surface area per unit change in hydraulic head

S= ss . b (confined)

ss= specific storage (m^-1)
b= aquifer thickness (m)

Question 4

Specific storage

Answer 4

symbol: ss

The amount of water per unit volume of a saturated formation that is stored or expelled due to:

a) the compressibility of the mineral matrix
b) the compressibility of the pore water

Question 5

If the head decreases in an aquifer, the affects are:

Answer 5

a) internal pressure goes down
b) mineral grains will rearrange to a more compact form
c) pore water will expand, expelling more h2o

Question 6

Specific storage formula

Answer 6

ss= pw . g(a+n . B)

a= compressibility of the mineral matrix (Pa^-1, 1/N/m2)
n= porosity 
B= compressibility of water (Pa^-1, 1/N/m2)

Question 7

Storativity in unconfined aquifers

Answer 7

S= Sy + Ss . b

Sy= specific yield (as the water table falls, water drains from the aquifer) 
Ss= specific storage (m^-1)
b= aquifer thickness (m)

Question 8

Volume of water drained from an aquifer as the head is lowered formula

Answer 8

Vw= S . A . >h

Vw= volume of water drained (m3)
S= storativity 
A= surface area overlying the drained aquifer (m2)
>h= average decline in the head