Consider two horizontal layers of an aquifer as shown in figure. Each layer is isotropic and homogeneous. Flow is parallel to the stratification. Thickness and horizontal hydraulic conductivity of layer-1 are $h_{1}$ and $K_{1}$, respectively. Thickness and horizontal hydraulic conductivity of layer-2 are $h_{2}$ and $K_{2}$, respectively, where $h_{1}$ is not equal to $h_{2}$. The equivalent horizontal conductivity $K_{x}$ for the aquifer system is given by ____________.
- $K_{x}=\frac{K_{1} \cdot h_{1}+K_{2} \cdot h_{2}}{h_{1}+h_{2}}$
- $K_{x}=\frac{K_{1}+K_{2}}{2}$
- $K_{x}=\frac{K_{1} \cdot h_{2}+K_{2} \cdot h_{1}}{h_{1}+h_{2}}$
- $K_{x}=\sqrt{K_{1} \cdot K_{2}}$
