Verde Watershed Research
 

Digital Hydrogeologic Framework Models and Implications for Fault Scaling, Upper Verde River Headwaters, Arizona

Matt Fry
Graduate Student
M.S. Geology Program
Northern Arizona University
mcf33@nau.edu
Advisor: Dr. Abe Springer
 

Two digital hydrogeologic framework models (DHFMs) of the Verde River headwaters region have been created and presented to stakeholders in the region; one of the Paulden area, and one of Big Chino Basin. Because the headwaters region of the Verde River is diverse geological terrain, conventional two-dimensional hydrogeological maps and display products have been inadequate to help understand and describe the sources of water for the springs which form the headwaters for the perennial reach of the Verde River below Paulden, Arizona.

The objectives of the study were to: (1) collect existing interpreted borehole data for the study areas, (2) create two 3-D DHFMs of the study areas, and (3) create and present an interactive visualization for each study area. Study objectives were met by first summarizing interpreted well log data from a variety of sources into a single database. Two DHFMs were created, along with databases constructed utilizing stratigraphic contacts digitized from geologic maps, and geophysical data used to define basement geometry of basins located in the study areas. The DHFMs were displayed to relevant stakeholders in the Verde River headwaters area to increase their understanding of the subsurface geologic and hydrogeologic relationships.

The DHFMs were created using EarthVision (Dynamic Graphics Inc., Alameda, California 2002), which was selected because of the number of faults present in the study areas and the desire to model the faults as three-dimensional planar features, to determine their effect on the hydrogeologic system. The Paulden area and Big Chino Basin DHFMs were able to accurately portray surficial and subsurface geology with respect to both stratigraphy and geologic structures. Development of the DHFMs allowed for incorporation of various data sets from different sources into the individual models. Viewing all data simultaneously greatly increased understanding of the geologic and hydrogeologic relationships of those who viewed the model visualizations.

Through application of a fault scaling relationship in the Paulden area DHFM, five faults with uncertain lengths were more accurately defined by re-assigning length values closer to the expected value. This allowed for a better definition of the linkages between faults in the Verde River headwaters area, and a more thorough understanding of the hydrogeologic setting and processes of the region. In general, isolated clusters of faults are present throughout the Paulden area DHFM, but these clusters show no linkage to other clusters. This determination was made because adjacent fault clusters are farther apart than the longest fault contained in any one cluster. Locations of the Upper Verde River springs and the beginning of perennial flow at the north end of Stillman Lake correlate to locations of faults, but connectivity between faults appears to play little role in determining groundwater flow-paths in the Verde River headwaters region.

DHFMs have several benefits that make them superior to traditional 2-D products. First, the models are interactive. They can be viewed at different angles and scales to help understand complex hydrogeologic relationships. Second, they can be sliced and vertical exaggeration can be manipulated to help view subtle changes in subsurface geologic relationships. Finally, because the DHFMs are in a digital format, they can be easily updated as additional data such as new well logs or new geophysical data, become available. The DHFMs can be used in combination with geochemical analysis by previous researchers to further constrain potential groundwater flow-paths within the Verde River headwaters region. In doing so, these existing tools will benefit future researchers in the development of a numerical groundwater flow model for the region. My thesis is available at: http://www4.nau.edu/geology/theses/fry06.pdf

Support for this research has been provided by the Arizona Water Protection Fund, Water Resources Research Center, and the Watershed Research and Education Program.