off routing, boundary condition-based coupling, and assimilation of multisource observation data. Water Resources Research, Feb 2010. URL: http://dx.doi.org/10.1029/2008WR007536, doi:10.1029/2008wr007536.">1</a>]</span>:</p>
<ol class="arabic simple">
<li><p>Subsurface flow equation:</p></li>
</ol>
<div class="math notranslate nohighlight">
\[S_{w}S_{s}\frac{\partial \psi}{\partial t} \,+\,\Phi\frac{\partial s_{w}}{\partial t} =\,\nabla.\,\left[K_{s}K_{r}\left(\nabla\psi\,+\,n_{z}\right)\right]\,+\,q_{ss}\]