Question

The storage coefficient of a confined aquifer is 6.8x10-4 determined by a pumping test. The thickness of the aquifer is 50 m and the porosity is 25%. Determine the fractions of the storage attributable to the expansibility of water and compressibility of the aquifer skeleton in terms of percentages of the storage coefficient of the aquifer.

Answer 1

Answer

given,

storage coefficient, S = 6.8 x 10⁻⁴

thickness of aquifer, t = 50 m

porosity of the aquifer, n = 25 % = 0.25

Density of the water, γ = 9810 N/m³

Compressibilty  of water,β = 4.673 x 10⁻¹⁰ m²/N

We know,

   S = γ t(nβ + α)

where, α is the compressibility of the aquifer

   6.8 x 10⁻⁴  =9810 x 50 x (0.25 x 4.673 x 10⁻¹⁰+ α)

     α = 1.269 x 10⁻⁹ m²/N

Expansability of water

            = n t β γ

            = 0.25 x 50 x 4.673 x 10⁻¹⁰ x 9810

            = 5.73 x 10⁻⁵