Advanced Groundwater Modeling Techniques for 3D Data

Building a realistic three-dimensional groundwater model often requires combining data from many sources. Borehole logs, LiDAR, elevation rasters, TINs, geologic surfaces, and sampled groundwater data can all provide important information about the subsurface. The Groundwater Modeling System (GMS) provides several tools for bringing these datasets together, visualizing them in 3D, and interpolating data for use in groundwater models.

Here are several tips for getting the most from 3D data in GMS.

Start With the Right 3D Data Structure

GMS 3D Scatter Points are particularly useful when measurements have X, Y, and Z coordinates. Each point can have associated datasets such as hydraulic conductivity, porosity, or contaminant concentration. GMS can interpolate these observations to 3D grids and meshes using methods such as inverse distance weighting and kriging.

However, 3D scatter points are not always the best starting point. Consider the type of data you have before converting it. Large elevation datasets, for example, may be better maintained as rasters or LiDAR rather than converted into millions of individual points.

Use Rasters and LiDAR for Detailed Elevation Data

Rasters are useful for representing continuous elevation data such as DEMs. GMS can display rasters as 3D point clouds and interpolate raster data to other GMS objects.

For projects with detailed terrain information, LiDAR can provide substantially more elevation observations than traditional elevation datasets. GMS includes tools specifically designed to manage large LiDAR datasets, including options for controlling the number of points displayed.

A useful practice is to keep high-resolution source data intact while creating appropriately sampled datasets for modeling and visualization.

Use TINs for Irregular Surfaces

Triangulated Irregular Networks (TINs) are another effective way to represent surfaces where data density varies. They can be particularly useful for geologic horizons, ground surfaces, and other irregularly sampled elevation data.

TINs can also serve as an intermediate format when moving information between different GMS objects and workflows.

Build 3D Geology From Boreholes and Horizons

Borehole data provides information about the subsurface that surface elevation datasets cannot provide. Use borehole contacts, cross sections, and interpreted horizons to establish the geometry of aquifers and confining units.

GMS can use Horizons and Solids to develop a three-dimensional representation of hydrostratigraphy. This provides a much stronger conceptual foundation than simply interpolating isolated measurements across the entire model domain.

Interpolate Only Where It Makes Sense

Whether using 3D scatter points, rasters, or other datasets, avoid assuming that interpolation automatically produces a realistic subsurface model. Sparse observations can result in large areas of uncertainty.

Consider the geology when selecting interpolation parameters. For example, vertical anisotropy may be important when hydraulic properties vary differently horizontally and vertically. The GMS 3D geostatistics tools specifically provide options for accounting for vertical anisotropy during interpolation.

Check the Results in 3D

Finally, inspect interpolated datasets using 3D views, cross sections, and iso-surfaces. Look for unexpected vertical trends, isolated values, abrupt transitions, and interpolation artifacts.

Remember that a smooth-looking 3D surface is not necessarily a realistic one. Compare the results against boreholes, mapped geology, known hydrogeologic boundaries, and other independent information before using the dataset as model input.

Final Thoughts

Effective 3D groundwater modeling in GMS is about more than choosing an interpolation method. The best results come from selecting the appropriate data structure for each dataset and combining 3D scatter points, rasters, LiDAR, TINs, boreholes, horizons, and solids to develop a defensible representation of the subsurface.

Download GMS and use its 3D tools today!