= Effective porosity
{title2=$\phi_e$}
<Effective porosity> is the pore-volume fraction accessible to connected transport under the specified measurement or model. It excludes isolated pore volume and may also exclude poorly exchanging regions on the transport timescale, so $0\leq\phi_e\leq\phi$ for total <porosity> $\phi$. In a simple mobile-volume model the mean <pore velocity> is $q/\phi_e$; the assumptions behind that model matter when interpreting tracer arrival times. A sample with total <porosity> $0.25$ but mobile pore fraction $0.20$ and <Darcy flux> $2.0\times10^{-5}\,\mathrm{m\,s^{-1}}$ has mobile mean <pore velocity> $1.0\times10^{-4}\,\mathrm{m\,s^{-1}}$. Woessner and Poeter discuss the role of connectivity and slowly exchanging pores.https://books.gw-project.org/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow/chapter/effective-porosity/{ref}
Back to article page
