Fig. 9.1 Phreatic aquifer with two horizontal strata

Consider the horizontally stratified aquifer shown in Fig. 9.1 above. The hydraulic conductivity of the upper strata of the unconfined aquifer is K₂ and that for the bottom strata is K₁. The depth of the bottom strata is a. Considering Dupuit assumption, the discharge per unit width at a distance x from the left reservoir can be expressed as,

Integrating from x = 0, h(x) = h₁ and x = L, h(x) = h₂, we can obtain

Equation (9.5) can be used to calculate the discharge through the horizontal stratified unconfined aquifer.

In case of n numbers of strata, the equation can be expressed as