Question

A confined aquifer 250m thick has bulk modulus of compression of 2.1x103kg/cm2 and porosity of 23%. Given the bulk modulus of elasticity of water is 2.4x104kg/cm2 and specific

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weight of water as 1000kg/m , Determine

A. The storage coefficient of the aquifer. B. Specific storage of an aquifer

Answer 1

storage coefficient

Volume of water released by a column of confined aquifer of unit cross sectional area under a unit decrease in the piezometric head.

The formula to find storage coeficient (S) is

Where

S -Storage coefficient  

- Unit weight of water =1000kg/m³ =

n-Porosity =23% =0.23

-Compressibility of pore water

Here we have bulk modulus of elasticity of water ,So Compressibility = 1/bulk modulus of elasticity of water

bulk modulus of elasticity of water=2.4x104kg/cm²

So Compressibility = 1/2.4x10⁴kg/cm² =41.67 x10^-6 cm²/kg

1 cm² =10-4 m² So =41.67 x10^-6 cm²/kg x10^-4 =41.67*10^-10 m²/kg

-Compressibility of the pores

bulk modulus of compression =2.1x103 kg/cm²

So   Compressibility = 1/2.1x103kg/cm² =4.76 x10^-4 cm²/kg =4.76 x10^-8 m²/kg

B-Thickness of aquifer =250 m

Substitute in the equation to get the answer

S =1000kg/m³*[(0.23*41.67 x10^-10 m²/kg)+4.76 x10^-8 m²/kg] *250m = 12.1396*10^-3m

storage coefficient S =12.1396*10^-3 m

b)Specific storage of an aquifer S_s

Specific storage of an aquifer Ss = 1000kg/m³*[(0.23*41.67 x10^-10 m²/kg)+4.76 x10^-8 m²/kg] =4.86 x 10^-5 /m

Specific storage of an aquifer Ss =4.86 x 10^-5 /m

storage coefficient S =12.1396*10^-3m