Note: linking WEAP to MODPATH is an advanced feature.
MODPATH is a groundwater particle tracking post-processing package that was developed to compute three-dimensional flow paths using output from steady-state or transient groundwater flow simulations by MODFLOW, the U. S. Geological Survey (USGS) finite-difference groundwater flow model. Its purpose is to evaluate advective transport through a model. MODPATH uses a semi-analytical particle tracking scheme that allows an analytical expression of the particle’s flow path (from the flow field results from MODFLOW) to be obtained within each finite-difference grid cell. Particle paths are computed by tracking particles from one cell to the next until the particle reaches a boundary, an internal sink/source, or satisfies some other termination criterion. The version of MODPATH that WEAP is designed to link to is MODPATH 5.0. (See http://water.usgs.gov/nrp/gwsoftware/modpath5/modpath5.html, or the MODPATH User Guide, for more information.) MODPATH tracks the trajectory of a set of particles from user-defined starting locations using the MODFLOW solution as the flow field. The particles can be tracked either forward or backward in time. Particle tracking solutions have a variety of applications, including the determination of zones of influence for injection and extraction wells.
In order to link a WEAP model to MODPATH, you must have already linked your WEAP model to a MODFLOW model. With an existing MODFLOW model, the only additional data that are required for MODPATH is porosity and where recharge should be applied.
The following topics describe the steps required to link WEAP to MODPATH: Load MODPATH Model, MODPATH Options and Particle Generation, MODPATH Porosity and Run the Models and View Results. See also MODPATH Link Technical Details.