Quantifying the effects of temperature and concentration on variable-density flow in numerical modeling of groundwater systems : implications for predictive uncertainty and data collection

Authors

Alyssa Marie Dausman, Florida International University

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Geosciences

First Advisor's Name

Michael C. Sukop

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Fernando Miralles-Wilhelm

Third Advisor's Name

William T. Anderson

Fourth Advisor's Name

Rene M. Price

Fourth Advisor's Committee Title

Christian Langevin

Date of Defense

11-3-2008

Abstract

Groundwater systems of different densities are often mathematically modeled to understand and predict environmental behavior such as seawater intrusion or submarine groundwater discharge. Additional data collection may be justified if it will cost-effectively aid in reducing the uncertainty of a model's prediction. The collection of salinity, as well as, temperature data could aid in reducing predictive uncertainty in a variable-density model. However, before numerical models can be created, rigorous testing of the modeling code needs to be completed. This research documents the benchmark testing of a new modeling code, SEAWAT Version 4. The benchmark problems include various combinations of density-dependent flow resulting from variations in concentration and temperature. The verified code, SEAWAT, was then applied to two different hydrological analyses to explore the capacity of a variable-density model to guide data collection.

The first analysis tested a linear method to guide data collection by quantifying the contribution of different data types and locations toward reducing predictive uncertainty in a nonlinear variable-density flow and transport model. The relative contributions of temperature and concentration measurements, at different locations within a simulated carbonate platform, for predicting movement of the saltwater interface were assessed. Results from the method showed that concentration data had greater worth than temperature data in reducing predictive uncertainty in this case. Results also indicated that a linear method could be used to quantify data worth in a nonlinear model.

The second hydrological analysis utilized a model to identify the transient response of the salinity, temperature, age, and amount of submarine groundwater discharge to changes in tidal ocean stage, seasonal temperature variations, and different types of geology. The model was compared to multiple kinds of data to (1) calibrate and verify the model, and (2) explore the potential for the model to be used to guide the collection of data using techniques such as electromagnetic resistivity, thermal imagery, and seepage meters. Results indicated that the model can be used to give insight to submarine groundwater discharge and be used to guide data collection.

Identifier

FI14062206

Comments

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Recommended Citation

Dausman, Alyssa Marie, "Quantifying the effects of temperature and concentration on variable-density flow in numerical modeling of groundwater systems : implications for predictive uncertainty and data collection" (2008). FIU Electronic Theses and Dissertations. 2740.
https://digitalcommons.fiu.edu/etd/2740