Analysis of Hydrochemical Data

Joseph Asante, Oberlin College

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In this activity students examine groundwater flow path based on hydraulic head data/ potentiometric surface and spatial variation of groundwater chemistry. Students analyze the data using AquaChem and Phreeqc which is integrated with AquaChem

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This is a laboratory activity designed for undergraduate hydrogeology course

Skills and concepts that students must have mastered

The concepts required for this activity are Darcy's law, drivers of groundwater flow, flownets, equilibrium concentration and speciation, flow regime and water chemistry/quality variations

How the activity is situated in the course

This activity is introduced after students have mastered the concepts and skills above and also performed this same set of activity on a small dataset using pencil and paper approach. This is a chance for them to work with a relatively large dataset using industry standard software AquaChem.


Content/concepts goals for this activity

- Use AquaChem software to analyze groundwater data- Integrate hydrochemical data with potentiometric surface data- Evaluate the plausibility of chemical analysis data using charge balance error calculation- Determine the ionic strength, activity coefficient, and the activities of major ions of groundwater- Determine the chemical species in groundwater- Determine IAP and SI of groundwater with respect to calcite, dolomite, halite, and gypsum- Use saturation indices, Piper and Schoeller diagrams to interpret groundwater flow

Higher order thinking skills goals for this activity

Integrate hydrogeology and low-temperature geochemistry data to examine groundwater movement

Other skills goals for this activity

students get a close encounter with analyzing data using AquaChem software

Description and Teaching Materials

lab11_hydrochem (Microsoft Word 555kB Jun6 13)

Teaching Notes and Tips


(i) Potentiometric surface map with your flowpaths drawn with arrows indicating groundwater flow direction in the vicinity of the selected wells(ii) For each of the groundwater samples, report in a table format their charge balance error, ionic strength, activity coefficient, and activities of the major ions.(iii) For each of the groundwater samples, please report in a table format their IAP and SI. Comment on the saturation state of the minerals (calcite, dolomite, halite, and gypsum) for each of the groundwaters(iv) Discuss and draw conclusions about groundwater flow from one sample location to another location based on your interpretations the values of saturation indices, plots of the chemical data on Piper and Schoeller diagram. Indicate this direction on the map (potentiometric surface map) provided. Does the flow direction indicated by the potentiometric surface agree with what you have delineated using groundwater chemistry?

References and Resources

Back, W., Hanshaw, B.B., 1970. Comparison of chemical hydrogeology of the carbonate Peninsulas of Florida and Yucatan. Journal of Hydrology, vol.10, 330 - 368.