This tutorial demonstrates several options for spatial parameterization of linear and polylinear features. In a groundwater model, these may represent entities such as streams, rivers, faults, or fracture networks. The hydraulic properties of these features may vary along their lengths. If this variability is relevant for a prediction of interest, then its representation in a model is important.
Pilot points comprise a useful two- or three-dimensional spatial parameterization device. This tutorial demonstrates how they can also be used in parameterization of one-dimensional entities that lie within the two- or three-dimensional domain of a groundwater model. Piecewise linear interpolation from pilot points to these entities is implemented using PLPROC – a PEST utility support program. The procedures described herein would normally be implemented as part of a PEST/PEST++ workflow, in which PLPROC parameterizes a model that is undergoing history-matching under the control of PEST or PEST++. Although the workflow described herein is specific to MODFLOW 6, the concepts that it demonstrates can be easily adapted to other models and/or file structures.