Aquifer Parameter Tool (Texture2Par) Development

SSP&A collaborated with Woodard and Curran to develop the aquifer parameter tool, Texture2Par, for use with Integrated Water Flow Model (IWFM) and MODFLOW models in support of California Department of Water Resources’ (DWR’s) Central Valley and statewide modeling efforts.

Texture2Par facilitates the assignment of aquifer parameter values directly to IWFM and MODFLOW model input files on the basis of sediment texture data acquired from stratigraphic logs. Aquifer properties that can be ascribed using Texture2Par are:

• Horizonal hydraulic conductivity
• Vertical hydraulic conductivity
• Specific yield
• Specific storage
• Texture2Par uses estimates of soil coarseness derived from stratigraphic logs to infer values for aquifer properties using power-law averaging techniques. Decreases in hydraulic conductivity with increasing depth resulting from compaction can also be accommodated with Texture2Par.

In the first release of Texture2Par, spatially distributed aquifer properties are computed by Texture2Par based on the model discretization; values for each aquifer property corresponding to end-member coarse and fine material types; and values for the percentage of coarse material at boring locations.

Only a small number of inputs is required to generate spatially distributed, potentially heterogeneous, parameterization of the model based on texture data, enabling Texture2Par to be integrated into a parsimonious calibration (parameter estimation) workflow that uses sediment texture data. To accommodate areas of differing cementation, compaction or sorting that leads to varying texture properties, Texture2Par incorporates pilot points enabling the values for aquifer parameters associated with purely coarse or fine textures (and fractions between) to vary in space.

Pilot points can be grouped with specific model nodes or cells to form distinct geological zones that exhibit different relationships between texture and aquifer properties. Example applications of Texture2Par include SVSim, C2VSim-FG developed using IWFM, and Arizona DWR’s Phoenix AMA Model developed using MODFLOW-NWT.

Highlights

SSP&A and Woodard and Curran are currently working with DWR to develop methods, tools, documentation, and case studies for formally integrating Airborne Electro-Magnetic (AEM) data into both (a) development of hydrogeologic conceptual models (HCMs) and (b) parameterization and calibration of groundwater models.

The development of HCMs and aquifer parameterization is instrumental in understanding the hydrogeologic systems that are being evaluated.

The first two phases of the project – literature review and method testing and development – were completed in December 2022. The project is anticipated to enhance the capabilities of Texture2Par and companion tools for HCM analysis by incorporating state-wide AEM data collected through recent geophysical surveys, thereby improving understanding of the geological and hydrogeologic structure of priority basins which are focus areas for water-resource modeling efforts.