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Kansas Geological Survey, Open-file Report 94-28b
Part of the Mineral Intrusion Project: Investigation of Salt Contamination of Ground Water in the Eastern Great Bend Prairie Aquifer


Characterization of the Saltwater Interface and Related Parameters

by G. W. Garneau, R. W. Buddemeier, and D. P. Young

A cooperative investigation by The Kansas Geological Survey and Big Bend Groundwater Management District No. 5
KGS Open File Report 94-28b
Released December, 1994

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Introduction

The Mineral Intrusion project has as one of its primary objectives the determination of the amount, distribution and movement of naturally occurring saltwater in the Great Bend Prairie aquifer. Background information on the objectives, setting and methods of the project may be found in Buddemeier et al. (1992) and the references contained therein.

The primary experimental means used to determine salt concentrations and distributions in the groundwater is determination of formation conductivity by logging the network of monitoring wells with a focused electromagnetic (EM) logging tool. The equipment and procedures used have been described in earlier reports (Young et al., 1993).

The data produced by this method consist of a vertical profile of conductivity values. These are determined primarily by the salinity (salt content) of the groundwater, but the absolute values are also affected to some extent by formation porosity, by the lithologic contributions to the total conductivity signal, and by instrument calibration.

In order to provide the best possible information on the groundwater characteristics, techniques have been developed to: (1) standardize instrument readings and correct for drift; (2) statistically remove a significant fraction of the overall lithologic contribution to the signal; and (3) convert the corrected conductivity values into equivalent concentrations of chloride ion in the groundwater. Because the ratio of chloride ion to salinity or total dissolved solids is nearly constant for salt derived from the Permian formation brines (Whittemore, 1993), the chloride values can be used to calculate total salt concentration if desired. These correction and conversion techniques have been described in detail by Young et al. (1993) and will not be repeated here.

Also discussed in the earlier report was work in progress on techniques for objectively fitting a physically realistic smooth curve to the sometimes noisy chloride and conductivity profiles, There are three reasons for wishing to do this. First, the low conductivity (upper) end of the profile is sufficiently noisy so that the lowest conductivity depth value that can be reliably read directly from the curve is about 100 mS/m. Although this provides a useful index of the observed transition zone depth, it corresponds to a chloride concentration of about 3300 mg/L, which is too salty for almost all uses. We therefore need a method for estimating the location of some more useful concentration threshold, such as 500 mg/L. Second, a number of our monitoring sites do not penetrate to the bottom of the transition zone, and it is extremely useful (as discussed below) to be able to estimate the characteristics of the portion of the transition zone that cannot be observed. Third, by fitting the data with an equation that is known to represent dispersion or diffusion processes in porous media, the quality of the fit can provide information on the extent to which that particular process is important in controlling the salt distribution at the site in question.

This report describes the curve-fitting technique employed, and how the fitted curve is used to estimate the elevation of the 500 mg/L chloride concentration. In addition, the integration of the chloride vs. depth profiles is described, as is how these results are used to calculate both total salt load (content) of the aquifer and the average salt concentration in the water column at a given site. The average concentration value is used to calculate a density correction to the observed fluid level. The results of these calculations are tabulated, but their applications are detailed and discussed in subsequent reports (OFR 94-28c-e).

Chloride Profile Curve-fitting and 500 mg/L depth estimation

The corrected conductivity profiles from different sites are individually reproducible, have a generally similar form, and reflect primarily the salinity of the ground water. However, the natural variability of the geohydrologic environment is reflected in the detailed variations in individual log profile structures-variations which complicate decisions about how to compare profiles in a consistent and generalizable fashion. One approach to developing the needed comparisons is to fit the field data to a mathematical model that is physically reasonable and provides a "cleaned up" version of the natural phenomenon for ease of calculation, manipulation, and comparison.

We have approached the problem of standardized comparisons by adopting a model which is known to accurately represent physical phenomena such as hydrodynamic dispersion or diffusion of a solute within a porous medium (Domenico and Schwartz, 1990) and for which an equation can be fit to the depth profile of corrected conductivity with a good correlation. The model selected is the normal distribution; in effect, we approximate the vertical conductivity profile within the transition zone as the cumulative distribution function of the Gaussian "bell-shaped curve." A normal distribution represents the characteristic probability distribution of a sampled variable (x) that exhibits a symmetric frequency distribution about its mean (M0) and is also a function of its standard deviation (M1):

norm(x,M0,M1) = (M1(2π)0.5)-1exp-[(x-M0)2/(2-MI2)]             (1).

The cumulative normal distribution function is the integral curve of the normal distribution function of equation I and produces a characteristic S-shaped (sigmoidal) profile that remains a function of the distribution mean and standard deviation. Cumulative normal distributions have been used successfully to characterize the freshwater-saltwater transition zone profile in an unconsolidated coastal aquifer (Schmorak and Mercado, 1969). In this earlier study, significant deviations from the normal distribution profile were found to be directly related to non-steady-state conditions caused by pumping above the transition zone that resulted in the upward movement of the interface as defined by the 50% concentration level in the transition zone.

Since the equations fitted to the various profiles produce idealized curves of exactly the same form, the fitted profiles can be quantitatively compared. An additional advantage is that the equation provides a consistent picture of that part of the curve that is of greatest interest but most subject to uncertainty and distortion-the upper fresh-water limit of the transition zone where deteriorating water quality begins to affect possible uses.

The simplest approach to fitting the corrected EM logs to normal distributions is to convert the corrected conductivities [Cm'; Young et al., (1993)] into chloride concentrations expressed as percentages of the maximum concentration of 42,000 mg/L. The value of 42,000 mg/L was chosen as the maximum end-member concentration based on an approximate average of the higher chloride concentrations observed in wells screened in the Permian (sites 5, 6, and 8) (D. O. Whittemore, pers. comm.). Chloride percentage concentrations (Cl%) were calculated using the equation:

Cl% = MAX[40,(Cm'-18)/0.02388+40]/420             (2).

Equation 2 sets the minimum concentration at 40 mg/L because this value represents the typical minimum level for the upper aquifer determined at site 50 (Whittemore, 1993). The other unit-conversion coefficients used in equation 2 are: 18 mS/m [the baseline aquifer conductance--eqn. 4, Young et al., (1993)]; 0.02388 mS/m per mg/L [the linear regression slope--Fig. 9, Young et al., (1993)]; and 40 mg/L (again the baseline chloride concentration at site 50) is added back to maintain the minimum water concentration. The conductivity log derived concentration value is then divided by 420 to express the value as a percentage of 42,000 mg/L such that a value of 21,000 mg/L becomes 50%.

The transition zone region (D1 to D2; Fig. B1A) used for curve fitting was selected by visual inspection of the chloride concentration profile. D1 locates the depth of the deepest portion of the profile consistently below 500 mg/L. D2 is the depth of either the last point on the profile (for incomplete profiles to bedrock) or the depth of the consistently highest concentration on the profile above bedrock. The transition zone region is then plotted on depth-normal probability axes and fitted with a least-squares line (Fig. B1B). The cumulative distribution function is represented by a straight line on the depth-probability axes. The equation for the fitted line, shown on Fig. B1B, contains the mean (M0) as the offset and standard deviation (M1) as the slope that defines the normal distribution of equation 1, is plotted on Fig. B1C, and the cumulative normal distribution shown in Fig. B1D. Because the concentrations are all expressed as a percentage of 42,000 mg/L, the mean (M0) is the depth of the 21,000 mg/L (50%) concentration of the fitted transition zone and the standard deviation (M1) indicates the thickness of the fitted transition zone (M0 + 2M1 = -95% of transition zone area). Because the equation of the curve is fixed, the curve-fitting process can also be adapted to the characterization of the complete transition zone by extension of the fitted line for wells having logs that only partially penetrate the transition zone such as the example from site 11 illustrated in Fig B1.

Figure B1-Example (site 11) of cumulative normal distribution fit to transition zone (TZ). A. DI and D2 indicate range of TZ to be used for fit. TZ is incomplete to bedrock because of well obstruction. B. TZ scaled to percent of 42,000 mg/L and plotted on depth-normal probability axes. Equation of fitted line and correlation coefficient (R) are shown with location of 500 mg/L (1.19%) concentration. C. Normal distribution represented by fitted line in part B: M0 = mean; M1 = standard deviation. D. Cumulative distribution function (dashed line) with chloride concentration profile locates depth of estimated 500 mg/L concentration of TZ and completes TZ profile to bedrock.

Example (site 11) of cumulative normal distribution fit to transition zone (TZ).

The means (M0), standard deviations (M1), and correlation coefficients (R, Fig. B1B) generated by the curve-fitting process represent parameters that characterize the transition zone, along with the actual conductivity values at selected points on the curve. Systematic changes in these parameters represent detectable changes in the freshwater-saltwater transition zone profile. The correlation coefficient (R) indicates the goodness-of-fit of the cumulative distribution function model to the transition zone at each site. The highest values tend to be at sites that generally have large and distinct transitions from fresh to salt water. Weak transition zones are indistinct, noisier, and thus tend to produce lower correlation coefficients. Changes in the correlation coefficient with time may reflect changes in the freshwater-saltwater distribution at a particular site as the transition zone either shifts towards more (increasing R) or less (decreasing R) ideal behavior.

The curve-fitting process allows the elevation of points near the upper and lower extremes of the transition zone to be estimated. For example, the depth of the 500 mg/L level can be estimated from the normal distribution curve fit with the following formula: M0+M1 * NORM(1.19) where M0 and M1 are the mean and standard deviation (Table B1) and NORM(1.19) is the normal distribution function (equation 1) of 500 mg/L expressed as a percentage of 42,000 mg/L (= 1.19%). The values of D1, D2, M0, M1, R, and the depth to the 500 mg/L concentration are tabulated for all sites that have a transition zone in Table B1.

Table B1--Curve-fitting statistics from logs with a transition zone.

Site Date D1 D2 M0
(mean)
M1
(std dev)
R
(corr)
Depth to
500 mg/L
Depth
change
1 3/26/93 90 127.7 133.18 17.07 0.9909 94.6  
1 4/15/94 90 127.7 134.54 17.894 0.9892 94.1 -0.5
3 5/19/93 94 119 197.41 43.008 0.8229 101.15  
3 4/13/94 94 119 192.14 39.927 0.8102 101.85 1.7
4 4/22/93 80 100 177.57 49.714 0.764 65.144  
4 4/13/94 80 100 165.23 44.262 0.8814 65.127 -0.017
5 9/17/93 66 106 98.876 12.641 0.972 68.288  
5 10/16/93 66 106 96.891 13.018 0.9755 67.452 -0.836
5 4/19/94 66 106 97.269 12.539 0.9754 68.912 1.46
6 4/19/93 bad log data
6 4/13/94 78 97 156.2 31.731 0.88445 84.445  
8 4/21/93 500 mg/L set at bedrock depth 117  
8 4/7/94 500 mg/L set at bedrock depth 117 0
9 4/25/93 40 79.5 90.065 17.336 0.5944 50.859  
9 4/14/94 40 79.5 88.037 16.182 0.5655 51.442 0.583
10 4/18/93 111 126 164.71 24.533 0.81843 109.23  
10 4/7/94 111 126 160.34 21.824 0.82634 110.99 1.76
11 3/27/93 82 167.1 216.97 60.108 0.9277 81.038  
11 5/20/93 82 167.1 221.95 64.422 0.9289 76.259 -4.779
11 7/9/93 82 167.1 220.58 63.57 0.9286 76.819 0.56
11 7/30/93 82 167.1 220.22 63.285 0.9279 77.103 0.284
11 9/22/93 82 167.1 221.78 65.076 0.9276 74.611 -2.492
11 10/13/93 82 167.1 221.69 65.06 0.9291 74.56 -0.051
11 4/8/94 82 167.1 226.16 66.184 0.912 76.429 1.869
16 3/25/93 122 187 176.97 21.62 0.9691 128.08  
16 5/19/93 122 187 177.19 21.454 0.9695 128.67 0.59
16 7/8/93 122 187 177.19 21.757 0.9686 127.99 -0.68
16 7/31/93 122 187 176.88 22.301 0.9734 126.44 -1.55
16 9/8/93 122 187 176.03 19.329 0.9773 132.31 5.87
16 10/21/93 122 187 176.88 22.319 0.9704 126.41 -5.9
16 3/31/94 122 187 176.63 21.89 0.974 127.13 0.71999
17 3/25/93 61 100 111.1 20.366 0.9412 65.046  
17 5/19/93 61 100 112.15 21.578 0.9446 63.348 -1.698
17 7/8/93 61 100 112.49 21.759 0.9447 63.281 -0.067
17 7/28/93 61 100 112.95 22.45 0.9455 62.178 -1.103
17 9/8/93 61 100 111.01 20.179 0.9384 65.372 3.194
17 10/21/93 61 100 111.08 20.447 0.9409 64.843 -0.529
17 4/1/94 61 100 111.02 20.488 0.9395 64.681 -0.162
18 3/25/93 107 172 182.26 31.753 0.8504 110.45  
18 5/21/93 107 172 183.84 33.194 0.8618 108.77 -1.68
18 7/9/93 107 172 183.09 32.716 0.85 109.1 0.33
18 7/29/93 107 172 183 32.624 0.844 109.22 0.12
18 10/14/93 107 172 182.55 32.282 0.8482 109.55 0.33
18 4/8/94 107 172 181.63 31.233 0.8407 110.99 1.44
19 4/19/93 142 163 237.37 41.181 0.78367 144.23  
19 4/7/94 142 163 237.49 41.545 0.78048 143.54 -0.69
21 5/20/93 80 136.1 161.27 34.198 0.9653 83.934  
21 4/7/94 80 136.1 160.13 32.164 0.9642 87.387 3.453
22 3/25/93 133 204 198.15 25.648 0.9338 140.15  
22 5/21/93 133 204 197.44 24.721 0.944 141.53 1.38
22 7/9/93 133 204 197.91 24.926 0.9262 141.53 0
22 7/30/93 133 204 197.93 25.114 0.9271 141.14 -0.39
22 10/14/93 133 204 197.08 24.427 0.938 141.84 0.7
22 3/31/94 133 204 197.82 24.549 0.9523 142.3 0.46001
23 4/20/93 52.5 82 123.87 21.585 0.5614 75.05  
23 4/19/94 52.5 82 158.41 40.539 0.6778 66.732 -8.318
24 4/20/93 88 112 146.88 24.408 0.86403 91.68  
24 4/19/94 88 112 148.55 25.444 0.8805 91.008 -0.672
25 3/28/93 8 38 35.675 11.43 0.9346 9.827  
25 7/31/93 8 38 34.896 11.427 0.901 9.053 -0.774
25 9/14/93 8 38 34.9 11.64 0.8947 8.577 -0.476
25 10/22/93 8 38 34.91 11.568 0.8944 8.748 0.171
25 4/4/94 8 38 35.56 11.099 0.9477 10.46 1.712
26 4/20/93 64 102 102.11 12.625 0.9278 73.56  
26 4/15/94 64 102 106.61 17.432 0.9788 67.19 -6.37
27 4/20/93 53 66 78.229 7.5943 0.9907 61.054  
27 4/15/94 53 66 84.086 11.187 0.9905 58.788 -2.266
29 4/25/93 94 150 254.31 67.954 0.634 100.64  
29 4/7/94 94 150 248.73 64.379 0.6457 103.13 2.49
30 4/25/93 85 132 216.98 48.91 0.5368 106.36  
30 4/14/94 85 132 204.65 42.662 0.4906 108.17 1.81
31 4/20/93 73 90 196.27 52.737 0.8467 77.008  
31 4/15/94 73 90 192 50.257 0.8138 78.345 1.337
32 4/24/93 75 135 158.26 31.292 0.6085 87.497  
32 4/19/94 75 135 151.87 27.745 0.551 89.126 1.629
33 5/20/93 120 139 191.41 26.976 0.794 130.41  
33 4/7/94 120 139 176.71 18.718 0.8117 134.38 3.97
35 4/21/93 115 142 186.37 27.447 0.8686 124.3  
35 4/20/94 115 142 188.79 28.937 0.8685 123.34 -0.96001
36 4/21/93 121 188 202.18 31.618 0.9544 130.67  
36 9/16/93 121 188 199.77 28.096 0.9635 136.23 5.56
36 4/14/94 121 188 203.65 32.828 0.9462 129.41 -6.82
37 4/21/93 212 233 260.55 17.497 0.902 220.98  
37 4/13/94 212 233 259.04 16.663 0.9271 221.36 0.38
38 4/21/93 150 177 198.04 19.209 0.8461 154.6  
38 4/14/94 150 177 197.33 18.805 0.8577 154.8 0.2
39 10/22/93 500 mg/L set at bedrock depth 55  
39 4/20/94 500 mg/L set at bedrock depth 55 0
42 4/22/93 74 149 187.52 37.412 0.93 102.91  
42 4/14/94 74 149 188.01 37.263 0.9392 103.74 0.82999
43 4/22/93 40 55 61.092 7.1996 0.9387 44.81  
43 4/19/94 40 55 60.55 6.8257 0.938 45.113 0.303
49 6/22/94 40 70 87.13 17.6 0.9264 102.7  
SP 4/17/93 123 180 167.27 16.4 0.9766 130.18  
SP 5/20/93 123 180 166.63 16.224 0.9743 129.94 -0.23999
SP 7/8/93 123 180 166.17 15.487 0.969 131.14 1.2
SP 7/27/93 123 180 166.04 14.993 0.968 132.13 0.99001
SP 7/29/93 123 180 166.09 15.343 0.9704 131.39 -0.74001
SP 9/18/93 123 180 166.63 17.193 0.9702 127.75 -3.64
SP 10/21/93 123 180 166.46 17.707 0.9655 126.41 -1.34
SP 3/24/94 123 180 166.07 16.676 0.9744 128.35 1.94
SP 3/31/94 123 180 166.08 16.473 0.9753 128.82 0.47
SP 4/13/94 123 180 166.01 16.166 0.97535 129.45 0.62999
SP 4/21/94 123 180 166.12 16.32 0.9752 129.21 -0.23999
SP 5/19/94 123 180 166.25 17.325 0.9762 127.07 -2.14
SD 4/17/93 123 158.3 165.45 15.87 0.8824 129.56  
SD 5/20/93 123 158.3 164.17 15.372 0.8888 129.41 -0.14999
SD 7/8/93 123 158.3 163.97 15.389 0.8918 129.17 -0.24001
SD 7/27/93 123 158.3 163.66 14.788 0.8795 130.22 1.05
SD 7/29/93 123 158.3 163.85 15.154 0.8863 129.58 -0.64
SD 9/18/93 123 158.3 163.92 15.128 0.9001 129.71 0.13
SD 10/21/93 123 158.3 164.18 15.327 0.8992 129.52 -0.19
SD 3/31/94 123 158.3 164.31 15.503 0.8608 129.25 -0.27
SD 4/13/94 123 158.3 164.06 15.311 0.87022 129.44 0.19
SD 4/21/94 123 158.3 164.27 15.574 0.8621 129.05 -0.39
SD 5/19/94 123 158.3 164.4 15.624 0.8656 129.06 0.009995

We emphasize that the use of standardized, fitted chloride curves is an empirical approach that supports research purposes and comparisons over time and space. The standardized salinity curves can also be used for salt-budget calculations. However, this approach is not essential to a basic description and understanding of saltwater distribution, and it can not replace interpretation of actual log measurements and chemical analyses in cases of site-specific management and assessment, where the details of the local context will be important.

The basic assumption of the curve fitting process is that the transition zone begins (<500 mg/L) at some point in the aquifer and increases with depth to the bedrock. Therefore, the process can only be successfully applied to logs from sites that have a distinct transition zone (or at least some portion of) that displays this pattern. Sites that are listed as saline transition zone sites in OFR 94-28c that can't be processed by the curve-fitting techniques described above (not included in Table Bl) because they lack data from the necessary transition zone depth range are: 15, 40, and 51.

Deviations from the archetypal transition zone assumption may exist because of incomplete removal of background lithologic contributions to the conductivity signal; "perched" transition zones; or the presence of relatively saltier water in the upper aquifer compared with the lower aquifer possibly from evaporative enrichment, agricultural chemicals, or oil brine contamination. The actual first occurrence of water with a concentration of 500 mg/L may therefore be at a lesser depth than indicated from the curve fitting process because of the ambiguous situations mentioned above. The selection of the depth range to be used for curve fitting (D I to D2) is an attempt to include as much of the profile extending to the bedrock as possible, exclude possible ambiguities, and to maximize (high R value) the fit to a cumulative distribution function. The relative success of the curve fitting process can be assessed by the R value: most sites consistently exceed 0.85; sites where R is less than 0.85 have less distinct and broad (M1 > 40 ft) transition zones that are most subject to distortions due to the presence of ambiguities.

Concentration levels calculated from the fitted profiles, such as the 500 mg/L depth, are intended to represent estimates of idealized, vertically controlled transition zone values as a product of possible hydrodynamic dispersion or diffusion processes starting with an original source brine with a concentration of 42,000 mg/L. The use of 42,000 mg/L chloride as an assumed bedrock limit of the upper end of the transition zone is an estimate based on the limiting concentration. We are aware that in some locations the transition zone extends into the bedrock, and that the actual maximum bedrock concentration may be less than 42,000 mg/L. As part of future work we will explore the effects of this assumption and the utility of alternative approaches. It is presented here as an illustration of the utility of a standardized comparison technique, and an initial estimate of some key parameters. Biases introduced by this assumption should have little effect on the use of the parameters to evaluate changes at a single site. Where the assumption is inaccurate, it will tend to skew the results toward higher salt inventories and sharper transition zones than may actually be the case.

Work in Progress

The following sections represent work in progress because the analysis so far has concentrated on sites in the northern Mineral Intrusion study area.

Salt inventory

The integrated salt load within the aquifer at each site is determined by calculating the area underneath the chloride concentration profile derived from the corrected conductivity log between the water table (wt) and the bedrock (br). For sites lacking a complete profile to bedrock, the cumulative distribution function fitted to the transition zone (described above) is used to estimate the missing section of the chloride concentration profile. Sites requiring extrapolation of the chloride profile were: 1, 5, 11, and 21. The area (A) was calculated by using the curve integration function in KaleidaGraphtm software running on a Macintosh Quadra. The integrated area (A) under the curve is based on the Riemann sum:

equation for integrated area

where: Cl(x) is the concentration (mg/L) at depth x, Δx = 0.1 ft, and from the fundamental theorem of calculus:

equation for integrated area

provided that f(x) is continuous and its derivative exists between a and b. The total mass of chloride per unit aquifer surface area is:

Cl(mg/ft2) = 28.32An             (5)

where A is the area under the depth profile of chloride concentration (mg-ft/L); 28.32 is a volumetric conversion factor (L/ft3); and n is effective aquifer porosity (unitless; assumed to be 0.16). The total chloride mass is a measure of the salt load for that portion of the aquifer. Table B2 includes the area (A), the chloride mass, and the equivalent saturated thickness at 42,000 mg/L required to equal the mass at sites in the northern part of the study area. Further discussion of these results and their implications will be found in OFR 94-28c and e.

Table B2 part 1--Salt Inventory at some monitoring well sites in the Mineral Intrusion study area (1993).

Site.well no. Depth to
bedrock
Depth to
water table
Area under
chloride
profile
Chloride
mass per
unit area
Equivalent
42k concen.
sat. thick
1.1 146 5.3 6.43E+05 2.91E+06 15.308
SP 186 10.8 7.96E+05 3.60E+06 18.94
3.1 130 25.73 33561 1.52E+05 0.79907
4.1 129 8.7 1.91E+05 8.66E+05 4.5492
5.1 181 1.77 3.06E+06 1.39E+07 72.775
8.1 118.3(1) 8.8 68715 3.11E+05 1.6361
9.1 87 9 1.96E+05 8.89E+05 4.6693
10.1 156 18.3 84985 3.85E+05 2.0234
11.1 208 13.5 8.65E+05 3.92E+06 20.592
16.1 220 11.98 1.68E+06 7.60E+06 39.915
17.1 114 11.6 2.49E+05 1.13E+06 5.9393
18.1 214 19.25 8.52E+05 3.86E+06 20.295
21.1 137 21.6 2.67E+05 1.21E+06 6.3524
22.1 215 16.1 8.07E+05 3.66E+06 19.208
23.1 94 21.42 41453 1.88E+05 0.98698
24.1 123 21 3.65E+05 1.66E+06 8.6993
25.1 98 6.3 1.31E+06 5.95E+06 31.241
26.1 177 6.8 9.52E+05 4.31E+06 22.661
27.1 104 10.12 82905 3.76E+05 1.9739
30.1 138 14.54 56876 2.58E+05 1.3542
31.1 93 13.65 37273 1.69E+05 0.88746
32.1 172 2.6 2.48E+05 1.12E+06 5.9067
36.1 195 28 4.26E+05 1.93E+06 10.15
37.1 240 58.63 95705 4.34E+05 2.2787
42.1 160 13.03 1.53E+05 6.91E+05 3.6311
43.1 65 4.87 71699 3.25E+05 1.7071
50.1 223 26.15 13657 61885 0.32518
51.1 200 17.3 23314 1.06E+05 0.5551
52.1 221 30.79 15816 71667 0.37658
Notes:
(1) Depth to bedrock changed from 117 ft based on inspection of conductivity log.
Depths and thicknesses in feet; Area = (mg-ft)/L; Mass (mg/sq. ft).

Table B2 part 2--Salt inventory at some monltonnc well sites In the Mineral Intrusion study area (1994).

Site.well no. Depth to
bedrock
Depth to
water table
Area under
chloride
profile
Chloride
mass per
unit area
Equivalent
42k concen.
sat. thick
1.1 146 6.35 6.10E+05 2. 76E+06 14.517
SP 186 11.3 8.05E+05 3.65E+06 19.172
3.1 130 20.54 32818 1.49E+05 0.78138
4.1 129 7.87 2.17E+05 9.82E+05 5.1603
5.1 181 2.08 3.05E+06 1.38E+07 72.522
8.1 118.3(1) 11.1 75413 3.42E+05 1.7955
9.1 87 9.36 2.07E+05 9.39E+05 4.9332
10.1 156 13.75 79998 3.62E+05 1.9047
11.1 208 11.39 8.04E+05 3.64E+06 19.135
16.1 220 7.64 1.66E+06 7.50E+06 39.412
17.1 114 10.54 2.57E+05 1.16E+06 6.1104
18.1 214 11.02 8.59E+05 3.89E+06 20.454
21.1 137 23.07 2. 16E+05 9.80E+05 5.1505
22.1 215 12.71 8.09E+05 3.67E+06 19.267
23.1 94 22.4 40763 1.85E+05 0.97055
24.1 123 23.9 2.57E+05 1.16E+06 6.1079
25.1 98 6.02 1.32E+06 6.ooE+06 31.535
26.1 177 8.76 1.03E+06 4.66E+06 24.47
27.1 104 11.22 1.09E+05 4.92E+05 2.5833
30.1 138 17.19 47496 2. 15E+05 1.1308
31.1 93 15.06 35320 1.60E+05 0.84096
32.1 172 9.1 2.60E+05 1.18E+06 6.1963
36.1 195 27.84 4.30E+05 1.95E+06 10.249
37.1 240 57.1 92821 4.21E+05 2.21
42.1 160 13.01 1.50E+05 6. 79E+05 3.5671
43.1 65 5.14 81034 3.67E+05 1.9294
49.1 106 1 196670 8.91E+05 4.6826
50.1 223 22.34 14846 67271 0.35348
51.1 200 13.68 24149 1.09E+05 0.57498
52.1 221 23.67 16859 76390 0.40139
Notes:
(1) Depth to bedrock changed from 117 ft based on inspection of conductivity log.
Depths and thicknesses in feet; Area = (mg-ft)/L; mass = (mg/sq. ft).

Variable density head correction

The applications of complete chloride concentration profiles for sites in the Great Bend Prairie aquifer include corrections for density effects on hydraulic head measurements and the determination of total salt mass for a particular site. Density-corrected head measurements will allow the development of an accurate horizontal and vertical component flow field within the aquifer. Together, the flow field and salt inventory will be used to determine the aquifer salt budget for the Mineral Intrusion study area.

Flow-field calculations involving water of high total dissolved solids (TDS) or higher or lower than normal temperatures requires that the effects of density be included in the formulations. For example, a salt water with a TDS of approximately 35,000 mg/L will have a density of 1.025 gm/cm3 as compared to pure water with a density of 0.999973 gm/cm3 at 4 deg C; pure water at 50 deg C has a density of 0.988047 gm/cm3 (Anderson and Woessner, 1992). These seemingly small changes in density can have a significant influence on the flow-field calculations, especially when potentiometric gradients are commensurately small to begin with. However, since the total thickness of the Great Bend Prairie aquifer is relatively small with small changes in temperature, only density variations due to changes in chloride concentration and not temperature need to be considered.

Figure B2 demonstrates the relationship between chloride concentration and density of seawater at 15 deg. C (Williams, 1962), the typical temperature (in situ) of ground water in the Great Bend Prairie aquifer. The linear relationship must be extrapolated to concentrations of 42,000 mg/L (the maximum groundwater concentration) because the relationship was developed for seawater with typical chloride concentrations of less than 25,000 mg/L. Although there are slight differences between the ionic ratios of seawater and of Permian formation brine, they are similar enough to justify the use of this relationship.

Figure B2--Conversion of chloride concentration to density.

Conversion of chloride concentration to density.

Figure B3 illustrates the concepts of hydraulic heads in variable density situations as described by Lusczynski (1961). The point-water head (Fig. B3A) is the field-measured fluid level, which is assumed to reflect the head of the well filled with water of uniform density equal to that occurring at the depth of the well screen. The fresh-water head (Fig. B3B) is the hypothetical head of the same well filled with uniformly fresh water. The environmental-water head (Fig. B3C) is the hypothetical head of the same well filled with the variable density water reflecting the actual vertical density gradient in the aquifer. The environmental-water correction can also be thought of as the freshwater correction reduced by an amount corresponding to the difference between the salt mass in fresh water and that in the actual (environmental) water in the interval from the top of the zone of saturation to the well screen (Lusczynski, 1961). Because the environmental-water head correction reflects the actual vertical mass distribution in the aquifer and thus an approximation of the density-related, gravity-driven component of flow, this correction is used to calculate vertical gradients within the aquifer.

Figure B3--Heads in ground water of variable density (after Lusczynski, 1961).

Heads in ground water of variable density (after Lusczynski, 1961).

For assessing the probable rate of inflow of saltwater from the Permian to the Great Bend Prairie aquifer formations, the critical head gradient is across the bedrock interface. In order to estimate that value on the basis of normalized densities, we use the difference between the calculated freshwater head of the Permian well (Hif, assumed to represent the density-corrected driving force for upward flow) and the environmental head at the bedrock datum (Hin, assumed to represent the density-corrected confining pressure of the overlying water column). These gradients are presented and discussed in reports OFR 94-28d and e.

The environmental head, based on the average density, is calculated quite simply from the integrated chloride profile area A (from eqn. 4 above) by dividing the value of A (mg-ft/L) by the saturated thickness of the aquifer. This provides the average chloride concentration over the depth in question; that value can be transformed into average density using the expression presented in Figure B2.

The results of head corrections for several sites, with measurements from 1993 and 1994, are contained in Table B3 parts 1 and 2. Two examples from Table B3 illustrate the necessity and precision of the head corrections. For site 5, the point-water heads indicate a recharge (downward) potential between the upper (number 3 well) and the lower (number 2 well) aquifer whereas the environmental-water corrected heads indicate a discharge (upward) potential. Because site 5 is located close to the gaining (discharge) Rattlesnake Creek and has an unusually thick and massive salt-water profile (Table B2), a discharge gradient appears to reflect the actual fluid potential within the aquifer. For site 8, the number 2 and 3 wells are both screened in the lower aquifer with approximately 30 ft of depth separation. The point-water heads for these two wells are approximately 0.3 ft different for both 1993 and 1994 measurements whereas the density-corrected heads are brought into coincidence to within 0.06 ft for 1993 and to within 0.01 ft for 1994 -- the much smaller gradients, at site 8, again reflecting congruity of fluid potentials. This high level of precision in matching the corrected heads indicates that very accurate potential flow field calculations, especially critical in the vertical direction within the Mineral Intrusion study area, can be calculated for the Great Bend Prairie aquifer if adequate elevation data are available.

Table B3 part 1--Variable-density head corrections for monitoring well sites in the northern and selected sites in the southern Mineral Intrusion study area 1993).

Site.well no. Depth to
Bedrock
Depth to
Screen
Depth to
Water Table
Depth to
Water
Density at
Screen (1)
Average
Density (2)
Point-water
Head (3)
Fresh-water
Head
Environmental-
Water Head
1.1 146 146 5.3 6.8 1.0171 1.0055 139.2 141.67 140.74
1.2 146 106 5.3 5.7 1.0036 0.99973 140.3 140.73 140.68
1.3 146 36 5.3 5.3 0.99936 0.9995 140.7 140.7 140.69
SP 186 197 10.8 20.9 1.0352 1.0054 175.2 181.88 180.75
3.1 130 120 25.73 28.31 1.0135 0.99974 101.69 102.99 102.93
3.2 130 65 25.73 25.73 0.9994 0.99941 104.27 104.27 104.26
4.1 129 217 8.7 5.8 1.041 1.0015 123.2 132.01 131.51
4.2 129 106 8.7 5.8 1.0004 1.0013 123.2 123.31 123.08
4.3 129 53 8.7 8.7 1.0009 1.001 120.3 120.37 120.27
5.1 181 193 1.77 1 1.0547 1.0222 180 190.64 186.17
5.2 181 92 1.77 3.26 1.0282 1.0019 177.74 180.31 180.06
5.3 181 40 1.77 1.77 0.99936 0.99973 179.23 179.23 179.21
8.1 118.3 (4) 237 8.8 25.1 1.0582 1.0002 93.2 105.69 105.48
8.2 118.3 (4) 116 8.8 15.8 1.0024 1.0001 102.5 102.81 102.71
8.3 118.3 (4) 87 8.8 15.5 1.0001 1.0002 102.8 102.86 102.77
8.4 118.3 (4) 46 8.8 8.8 0.99998 0.99955 109.5 109.52 109.51
9.1 87 86 9 9 1.0037 1.0027 78 78.34 78.018
9.2 87 62 9 8.8 1.0012 1.0004 78.2 78.301 78.223
9.3 87 38 9 9 0.99936 0.99955 78 78.001 77.99
10.1 156 160 18.3 22.9 1.0016 1.0001 133.1 133.42 133.27
10.2 156 143 18.3 22.7 1.0013 1 133.3 133.54 133.43
10.3 156 100 18.3 20.8 1.0004 0.99961 135.2 135.29 135.25
10.4 156 74 18.3 18.3 0.99961 0.99942 137.7 137.72 137.71
11 .1 208 237 13.5 31.89 1.0329 1.0053 176.11 183.01 181.51
11.2 208 61 13.5 13.5 1.0002 1.0002 194.5 194.54 194.48
16.1 220 243 11.98 29.2 1.0461 1.0101 190.8 200.81 198.05
16.2 220 198 11.98 19.25 1.0452 1.0065 200.75 208.96 207.45
16.3 220 80 11.98 11.98 0.99948 1.0003 208.02 208.03 207.94
17.1 114 129 11.6 45.7 1.0126 1.0026 68.3 69.407 68.946
17.2 114 102 11.6 10.8 1.0105 1.002 103.2 104.22 103.92
17.3 114 41 11.6 11.6 0.99936 0.99952 102.4 102.4 102.39
18.1 214 231 19.25 34.32 1.0157 1.0052 179.68 182.91 181.43
18.2 214 197 19.25 32.76 1.0189 1.004 181.24 184.46 183.44
18.3 214 45 19.25 19.25 0.99961 0.99961 194.75 194.76 194.74
21.1 137 145 21.6 25.2 1.015 1.0024 111.8 113.69 113.17
21.2 137 113 21.6 22.9 1.0047 1.0007 114.1 114.59 114.4
21.3 137 43 21.6 21.6 1.0003 1.0013 115.4 115.42 115.29
22.1 215 231 16.1 29.3 1.043 1.0048 185.7 194.52 193.17
22.2 215 206 16.1 24.7 1.0313 1.0036 190.3 196.1 195.15
22.3 215 35 16.1 16.1 0.99936 0.99936 198.9 198.9 198.9
23.1 94 122 21.42 24.22 1.008 1.0001 69.78 70.632 70.522
23.2 94 79 21.42 22.99 0.99995 1 71.01 71.046 70.977
23.3 94 44 21.42 21.42 0.99936 1.0008 72.58 72.581 72.484
24.1 123 131 21 23.8 1.0018 1.0041 99.2 99.462 98.73
24.2 123 86 21 21.2 0.99997 1.0056 101.8 101.84 101.17
25.1 98 120 6.3 11.4 1.0227 1.0185 86.6 89.142 86.711
25.2 98 95 6.3 12 1.0343 1.0181 86 88.906 87.001
25.3 98 44 6.3 6.3 1.0266 1.0123 91.7 92.73 92.076
26.1 177 190 6.8 16.2 1.0174 1.0068 160.8 163.95 162.47
26.2 177 118 6.8 11 .1 1.0154 1.0038 165.9 167.62 167.06
26.3 177 60 6.8 6.8 0.99961 0.99963 170.2 170.22 170.19
27.1 104 115 10.12 10.75 1.0018 1.0005 93.25 93.508 93.36
27.2 104 60 10.12 10.1 1.0005 1.0001 93.9 93.959 93.904
27.3 104 30 10.12 10.12 0.99994 1.0008 93.88 93.893 93.833
30.1 138 155 14.54 17.3 1.0026 0.99993 120.7 121.15 121.04
30.2 138 123 14.54 14.57 1.0003 0.99986 123.43 123.54 123.46
30.3 138 60 14.54 14.54 0.99936 0.99993 123.46 123.46 123.42
31.1 93 108 13.65 13.43 1.0017 0.99994 79.57 79.795 79.718
31.2 93 85 13.65 13.78 1.0004 0.9999 79.22 79.298 79.239
31.3 93 55 13.65 13.65 1.0002 0.99941 79.35 79.387 79.38
32.1 172 189 2.6 45.83 1.0018 1.0013 126.17 126.53 126.15
32.2 172 161 2.6 45.88 1.0022 1.0012 126.12 126.45 126.14
32.3 172 113 2.6 1.48 1.0025 1.0004 170.52 170.88 170.75
32.4 172 78 2.6 2.6 1.0002 0.99968 169.4 169.47 169.44
36.1 195 210 28 29.9 1.0286 1.0027 165.1 170.38 169.56
36.2 195 191 28 27.8 1.022 1.0023 167.2 170.91 170.25
36.3 195 146 28 26 1.0026 1 169 169.4 169.27
36.4 195 85 28 28 1.0004 0.99969 167 167.06 167.02
37.1 240 255 58.63 60.84 1.0024 1 179.16 179.76 179.54
37.2 240 235 58.63   1.0023 0.99996      
37.3 240 151 58.63 59.06 0.99947 0.99972 180.94 180.95 180.87
37.4 240 82 58.63 58.63 0.99951 0.99983 181.37 181.37 181.3
42.1 160 178 13.03 21.28 1.0059 1.0007 138.72 139.75 139.49
42.2 160 157 13.03 20.36 1.0042 1.0006 139.64 140.31 140.09
42.3 160 103 13.03 13.03 1.0007 0.99948 146.97 147.1 147.08
43.1 65 88 4.87 5.4 1.0023 1.0009 59.6 59.844 59.695
43.2 65 40 4.87 4.87 0.9996 0.99946 60.13 60.14 60.133
50.1 223 190 26.15 25.94 0.99952 0.9994 197.06 197.09 197.07
50.2 223 120 26.15 26.09 0.99936 0.99943 196.91 196.91 196.9
50.3 223 45 26.15 26.15 0.99936 0.99956 196.85 196.85 196.83
51.1 200 170 17.3 17.83 1.0011 0.99948 182.17 182.45 182.41
51.2 200 95 17.3 17.3 0.99941 0.99954 182.7 182.71 182.68
52.1 221 195 30.79 30.4 0.99952 0.99942 190.6 190.63 190.61
52.2 221 97 30.79 30.79 0.99954 0.99943 190.21 190.23 190.21
Notes:
(1) Median density across screened interval from processed loa profiles except for wells screened in bedrock (Depth to Screen > Depth to Bedrock)
where density is calculated from chloride concentration reported by Whittemore (1993).
(2) Average density calculated between water table and smaller of screen and bedrock depths.
(3) Bedrock depth used for datum at each site.
(4) Depth to bedrock changed from 117 ft based on inspection of conductivity log.

Table 83 part 2--Variable-density head corrections for monitoring well sites in the northern and selected sites in the southern Mineral Intrusion study area (1994).

Site.well no. Depth to
Bedrock
Depth to
Screen
Depth to
Water Table
Depth to
Water
Density at
Screen (1)
Average
Density (2)
Point-water
Head (3)
Fresh-water
Head
Environmental-
Water Head
1.1 146 146 6.35 6 1.0171 1.0052 140 142.49 141.59
1.2 146 106 6.35 6.51 1.0036 0.99973 139.49 139.92 139.87
1.3 146 36 6.35 6.35 0.99936 0.99945 139.65 139.65 139.65
SP 186 197 11.3 18.4 1.0352 1.0055 174.7 181.36 180.22
3.1 130 120 20.54 23.31 1.0117 0.99971 106.69 107.89 107.83
3.2 130 65 20.54 20.54 0.99939 0.99941 109.46 109.46 109.46
4.1 129 217 7.87 5.54 1.041 1.0017 123.46 132.28 131.74
4.2 129 106 7.87 3.16 1.0012 1.0015 125.84 126.03 125.78
4.3 129 53 7.87 7.87 1.001 1.0011 121.13 121.21 121.1
5.1 181 193 2.08 1.53 1.0547 1.0222 179.47 190.08 185.62
5.2 181 92 2.08 3.6 1.028 1.0017 177.4 179.94 179.71
5.3 181 40 2.08 2.08 0.99936 0.99955 178.92 178.92 178.91
8.1 118.3 (4) 237 11 .1 23.52 1.0582 1.0003 94.78 107.36 107.12
8.2 118.3 (4) 116 11 .1 17.19 1.0032 1.0002 101.11 101.49 101.38
8.3 118.3 (4) 87 11.1 16.86 0.99999 1.0003 101.44 101.49 101.39
8.4 118.3 (4) 46 11.1 11 .1 0.99998 0.99955 107.2 107.22 107.21
9.1 87 86 9.36 9.34 1.0037 1.0029 77.66 77.998 77.656
9.2 87 62 9.36 9.2 1.0013 1.0003 77.8 77.905 77.834
9.3 87 38 9.36 9.36 0.99936 0.99944 77.64 77.641 77.635
10.1 156 160 13.75 20.4 1.0016 1.0001 135.6 135.92 135.79
10.2 156 143 13.75 20.16 1.0012 0.99995 135.84 136.07 135.97
10.3 156 100 13.75 18.12 1.0003 0.99959 137.88 137.96 137.93
10.4 156 74 13.75 13.75 0.99956 0.99942 142.25 142.27 142.26
11.1 208 237 11.39 29.37 1.0329 1.0048 178.63 185.61 184.25
11.2 208 61 11.39 11.39 1.0003 1.0003 196.61 196.66 196.59
16.1 220 243 7.64 20.85 1.0461 1.0098 199.15 209.55 206.92
16.2 220 198 7.64 14.93 1.0445 1.0063 205.07 213.35 211.91
16.3 220 80 7.64 7.64 0.99936 0.99982 212.36 212.36 212.32
17.1 114 129 10.54 44.06 1.0126 1.0026 69.94 71.069 70.603
17.2 114 102 10.54 9.91 1.0106 1.002 104.09 105.13 104.83
17.3 114 41 10.54 10.54 0.99936 0.99954 103.46 103.46 103.45
18.1 214 231 11.02 26.44 1.0157 1.005 187.56 190.92 189.54
18.2 214 197 11.02 26.97 1.0192 1.0038 187.03 190.41 189.48
18.3 214 45 11.02 11.02 0.99957 0.99954 202.98 202.99 202.98
21.1 137 145 23.07 26.04 1.015 1.0019 110.96 112.83 112.4
21.2 137 113 23.07 23.93 1.0042 1.0004 113.07 113.51 113.36
21.3 137 43 23.07 23.07 0.99999 1.0008 113.93 113.94 113.85
22.1 215 231 12.71 24.57 1.043 1.0047 190.43 199.46 198.14
22.2 215 206 12.71 20.11 1.0305 1.0035 194.89 200.69 199.77
22.3 215 35 12.71 12.71 0.99936 0.99936 202.29 202.29 202.29
23.1 94 122 22.4 23.93 1.008 1.0001 70.07 70.925 70.814
23.2 94 79 22.4 21.95 1.0006 0.99969 72.05 72.124 72.085
23.3 94 44 22.4 22.4 0.99939 0.99942 71.6 71.602 71.594
24.1 123 131 23.9 25.94 1.0018 1.0028 97.06 97.317 96.778
24.2 123 86 23.9 24.15 0.99991 1.0036 98.85 98.887 98.415
25.1 98 120 6.02 11.8 1.0227 1.0187 86.2 88.733 86.292
25.2 98 95 6.02 12.64 1.0318 1.0182 85.36 88.038 86.128
25.3 98 44 6.02 6.02 1.0267 1.0121 91.98 93.021 92.381
26.1 177 190 8.76 16.72 1.0174 1.0075 160.28 163.42 161.79
26.2 177 118 8.76 12.61 1.0166 1.0042 164.39 166.21 165.59
26.3 177 60 8.76 8.76 0.99994 0.99983 168.24 168.27 168.24
27.1 104 115 11.22 11.52 1.0018 1.0009 92.48 92.736 92.538
27.2 104 60 11.22 11.05 1.0008 1.0004 92.95 93.023 92.945
27.3 104 30 11.22 11.22 1.0002 1.0013 92.78 92.797 92.715
30.1 138 155 17.19 18.59 1.0026 0.99984 119.41 119.85 119.76
30.2 138 123 17.19 17.15 1.0002 0.99976 120.85 120.94 120.88
30.3 138 60 17.19 17.19 0.99937 0.99974 120.81 120.81 120.78
31.1 93 108 15.06 14.3 1.0017 0.99992 78.7 78.923 78.848
31.2 93 85 15.06 14.6 1.0004 0.99988 78.4 78.477 78.42
31.3 93 55 15.06 15.06 0.99998 0.9994 77.94 77.967 77.96
32.1 172 189 9.1 48.64 1.0018 1.0015 123.36 123.71 123.29
32.2 172 161 9.1 47.87 1.0023 1.0014 124.13 124.47 124.11
32.3 172 113 9.1 4.95 1.0026 1.0006 167.05 167.41 167.25
32.4 172 78 9.1 9.1 1.0003 0.99981 162.9 162.97 162.92
36.1 195 210 27.84 28.43 1.0286 1.0028 166.57 171.9 171.07
36.2 195 191 27.84 27.65 1.0193 1.0024 167.35 170.62 169.94
36.3 195 146 27.84 24.83 1.0026 1.0001 170.17 170.57 170.43
36.4 195 85 27.84 27.84 1.0001 0.99971 167.16 167.21 167.16
37.1 240 255 57.1 59.09 1.0024 0.99999 180.91 181.52 181.31
37.2 240 235 57.1   1.0022 0.99993      
37.3 240 151 57.1 57.53 0.99944 0.99971 182.47 182.48 182.4
37.4 240 82 57.1 57.1 0.99944 0.99984 182.9 182.9 182.83
42.1 160 178 13.01 18.48 1.0059 1.0007 141.52 142.57 142.31
42.2 160 157 13.01 17.61 1.0039 1.0006 142.39 143.03 142.81
42.3 160 103 13.01 13.01 1.0006 0.99947 146.99 147.11 147.09
43.1 65 88 5.14 5.19 1.0023 1.0011 59.81 60.055 59.885
43.2 65 40 5.14 5.14 0.99955 0.99979 59.86 59.868 59.847
50.1 223 190 22.34 22.2 0.99952 0.99943 200.8 200.84  
50.2 223 120 22.34 22.29 0.99936 0.99946 200.71 200.71 200.69
50.3 223 45 22.34 22.34 0.99936 0.99956 200.66 200.66 200.64
51.1 200 170 13.68 14.17 1.0011 0.99948 185.83 186.11 186.08
51.2 200 95 13.68 13.68 0.99941 0.99954 186.32 186.33 186.3
52.1 221 195 23.67 28.83 0.99952 0.99942 192.17 192.2 192.18
52.2 221 97 23.67 23.67 0.9995 0.99945 197.33 197.34 197.33
Notes:
(1) Median density across screened interval from processed loa profiles except for wells screened in bedrock (Depth to Screen > Depth to Bedrock)
where density is calculated from chloride concentration reported by Whittemore (1993).
(2) Average density calculated between water table and smaller of screen and bedrock depths.
(3) Bedrock depth used for datum at each site.
(4) Depth to bedrock changed from 117 ft based on inspection of conductivity log.

References

Anderson, M.P., and W. W. Woessner. 1992. Applied Groundwater Modeling--Simulation of Flow and Advective Transport: Academic Press, Inc., New York. 381 p.

Buddemeier, R. W., M. A. Sophocleous and D. O. Whittemore. 1992. Mineral Intrusion--Investigation of Salt Contamination of Groundwater in the Eastern Great Bend Prairie Aquifer: Kansas Geological Survey, Open-File Report 92-25, 45 pp. [available online]

Domenico, P. A., and F. W. Schwartz. 1990. Physical and Chemical Hydrogeology: John Wiley and Sons, New York. 824 p.

Lusczynski, N. J. 1961. Head and flow of ground water of variable density: Jour. Geophys. Res., v. 66, n. 12, pp. 4247-4256.

Schmorak, S., and A. Mercado. 1969. Upconing of freshwater-seawater interface below pumping wells.: Water Resources Res., v. 5, p. 1290-1311.

Whittemore, D.O. 1993. Ground-water geochemistry in the mineral intrusion area of Groundwater Management District No. 5, south-central Kansas: Kansas Geological Survey, Open-File Report 93-2. [available online]

Williams, J. 1962. Oceanography: Little, Brown and Co., Boston.

Young, D. P., G. W. Garneau, R. W. Buddemeier, D. Zehr, and J. Lanterman. 1993. Elevation and variability of the freshwater-saltwater interface in the Great Bend Prairie aquifer, south-central Kansas: Kansas Geological Survey, Open-File Report 93-55.


Kansas Geological Survey, Geohydrology
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