Lab 2: Water Chemistry, Water Quality, and Groundwater Flow


Purpose: Interpretation of groundwater geochemistry data and relate chemical data to groundwater flow and geology.

We will work through three problems in the lab 4 of Lee and Fetter (1994). Please read all the following related background information BEFORE going to lab.

p.29-38 (lab 4) of Lee and Fetter
Table 11.2, p. 291-294, p. 329-331, and p.413 of Fetter.


Problem 1: Groundwater Maps - Front Range Urban Corridor

Working on questions 1 to 8 and 11 of p. 32 (skip question 9 and 10, no wells in the SW part of the map) BEFORE going to lab. Try to answer these questions as much as you could (You don't need to WRITE down your answers). We will discuss these questions in the lab.

Problem 2: Water Chemistry - Amargosa Desert

We will work on questions 2, 3, 4, 5 in the lab classroom (3 points each) You don't need to do unit conversions asked in question 1 (unless you insist). All the chemical concentrations have been converted to % for you (see table in the third page), so they are ready to be plotted in a Piper diagram (Wells 1-10 have been plotted in Fig. 4.5; Wells 11-15 have been left for you to plot). For question 5, comment on the direction of regional flow system in the Great Basin (Fetter p. 293-294). If toxic chemicals are leaking from the Nevada Test Site, will they contaminate the spring water 13 near Devil Holes (see Figure 4.6)?

Also Answer the following question:

Question 6: Among the various hydrochemical facies in your piper diagram, which one most likely represents groundwaters associated with carbonate rocks (consists of CaCO3 and CaMg(CO3)2)? 3 pts.





Problem 3: Water Quality - Amargosa Desert

1. Compute (1) hardness and (2) sodium adsorption ratio (SAR) values of groundwaters of each wells in Table 4.1. (5 pts)

2. Based on the water chemistry data (chemistry of individual ions and TDS in Table 4.1, and the calculated hardness and SAR data), comment on the suitability of each of the wells in the Amargosa Desert for both (1) domestic use and (2) irrigation. Also comment on whether the water from each wells will cause "scaling" (precipitation of carbonate minerals) problems. Complete the following table to answer the question. Domestic use should consider drinking water standards (Table 4.2 of Lee and Fetter or Table 11.2 of Fetter) and any indication of possible contamination (such as high NO3-). Water with hardness values greater than 150 mg/l is designated as being very hard (Freeze & Cherry, p 387) and may cause excessive scaling problem even though it may be still OK for domestic use. A low SAR (2 to 10) indicates little danger from sodium, high values of SAR (greater than 10) may cause the dispersion of clay particles and lead to the destruction of soil structure and soil erosion (Fetter, p 413). 10 pts



Well TDS hardness SAR Domestic Irrigation Cause Scaling?
(ppm) (ppm) (mmol/l) (OK or NO) (OK or NO) (Yes or NO)

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