## Hydrology

### Hydrologic Properties of Water-Bearing Materials

The quantity of ground water that an aquifer will yield to wells depends upon the hydrologic properties of the aquifer. The ability of an aquifer to transmit water is measured by its coefficient of transmissibility. The coefficient of transmissibility (T) of an aquifer is defined as the number of gallons of water that will move in 1 day through a vertical strip of aquifer 1 foot wide and the full thickness of the aquifer, under a hydraulic gradient of 100 percent, or 1 foot per foot, at the prevailing temperature of the water. The coefficient of permeability (P) is expressed as the rate of flow of water, in gallons per day, through a cross-sectional area of 1 square foot under a hydraulic gradient of 1 foot per foot. The coefficient of permeability can be computed by dividing the coefficient of transmissibility by the thickness (m) of the aquifer. The coefficient of storage (S) of an aquifer is defined as the volume of water it releases or takes into storage per unit surface area of the aquifer per unit change in the component of head normal to that surface. Under water-table conditions the coefficient of storage is practically equal to the specific yield, which is defined as the ratio of the volume of water a saturated material will yield to gravity in proportion to its own volume.

#### Purpose of Aquifer Tests

The hydrologic properties described above are determined from aquifer tests. Hydrologic coefficients resulting from aquifer tests are used in conjunction with the water-level contour maps to estimate the quantity of ground water moving laterally through the water-bearing formations. They are used to estimate the quantity of water being removed or returned to storage and the amount of local recharge. These tests also give an indication of the type and areal extent of the water-bearing materials.

#### Methods of Analyses and Test Results

Aquifer tests were made at 26 sites in Grant and Stanton counties. The tests were analyzed by the nonequilibrium method (Theis, 1935) or by the modified nonequilibrium method (Cooper and Jacob, 1946). These methods of analyses are also shown in U.S.G.S. WSP1536-E. The results of these tests are summarized in Table 5. The basic data for one of these tests are plotted in Figure 6. The coefficients of transmissibility obtained from these tests are plotted on Plate 11B in parentheses to distinguish them from the estimated coefficients to be described later.

Table 5--Results of aquifer tests, Grant and Stanton counties.

Well number Geologic
source
(a)
Coefficient of
transmissibility,
gpd/ft
Coefficient of
storage,
dimensionless
Grant County
27-36-15ddNpl, No153,0000.00014
27-37-29ccNpl, No52,100.00012 (b)
27-38-15daNpl, No63,400.00023 (b)
27-38-19cdNpl, No590,000.0048
27-38-22cbNpl, No159,000.00035
27-38-23caNpl, No71,000.00021
27-38-32bbNpl, No188,000.0024
28-36-11baNpl, No215,000.00022
28-38-12cbNpl, No50,600.00028
28-38-15cbNpl, No119,000.00060
28-38-27baNpl, No125,000.00021
29-35-15abNpl134,000.00038 (b)
29-38-35dbNpl, No45,000.00094 (b)
30-37-2ba2Npl, No29,600.00014 (b)
30-37-19aa2Npl56,000.00029 (b)
30-37-26daNpl, No145,000.0032
30-38-30acNpl, No337,000.00044 (c)
Stanton County
27-39-13acKd, Kc45,800
27-40-25cbNpl, No137,000.0048
28-39-12acNpl40,500.00011
28-39-20bdNpl, No188,000.00095
28-39-24cc2Npl, No465,000.0094
28-41-14aaNpl, No352,000.059
29-39-24ddNpl, No58,000.0011 (b)
30-40-24cdNpl, No, Kd97,500.0013
30-41-13ccNo, Kd137,000.044
a. Npl, Pleistocene deposits; No, Ogallala Formation;
Kd, Dakota Formation; Ke, Cheyenne Sandstone.
b. Pumped well may be partially penetrating.
c. See Figure 7.

Figure 6--Drawdown of water level in observation wells during 30-38-30ac aquifer test, July 27-31, 1960.

The values for T obtained from these tests were reduced to the field coefficients of permeability (P - T/m). The value used for m is not the total saturated thickness of the formations, but is the aggregate of effective thickness of the sand and gravel beds in the formation, based on the driller's and authors' interpretations of the well logs.

Because tests were made using wells screened opposite more than one aquifer, a trial and error method was used to determine P for each aquifer. Trial values of P were assigned to the sand of each aquifer, then multiplied by the aggregate thickness to obtain T. A trial T for the complete saturated sand section was then obtained by adding the individual values for T for each aquifer. This value for T was then compared with that obtained from the aquifer test. The process was continued until a permeability (P) was assigned to each aquifer that when combined with the aggregate thickness of the aquifers at each test site resulted in coefficients of transmissibility that were approximately the same as the coefficients obtained from aquifer tests. Using this method, the average coefficient of permeability was 2,200 gpd/ft2 for the Pleistocene aquifer and 1,250 gpd/ft2 for the Pliocene aquifer.

The coefficients (P) were then extended to other areas and used in conjunction with the drillers' logs to estimate the coefficients (T) as shown for well 27-35-4bbb. In this well there is a saturated section of 112 feet of sand and/or gravel in the Pleistocene deposits and 33 feet of Pliocene sand. Thus: (112 X 2,200) + (33 X 1,250) = 287,000 gpd/ft which is the coefficient (T) for the well site. The estimated transmissibilities obtained by this method are shown in brackets on Plate 11B.

The thickness of the sand and gravel used in the above estimates is not the total thickness of sand and gravel in the well described by the drillers. In many of the logs, the drillers, on the basis of their experience, assigned a yield number to each sand and gravel section of the aquifer. If a 10-foot section of aquifer contained clean sand and gravel and the material drilled easily, the driller probably would assign it a thickness of 10 feet. However, if the 10-foot section contained thin layers of silt or fine sand, the driller might assign it a thickness of 5 feet. In other words, the numbers shown in parentheses on the drillers' logs are the drillers' estimates of the yield from the intervals logged. The drillers total these numbers for the well and multiply by a coefficient to obtain the estimated yield of a well in gallons per minute. Where these estimates were not included in the drillers' logs, the equivalent thicknesses were estimated by the authors. The estimates of the authors were not included in the published logs but are computed as part of the coefficients of transmissibility on Plate 11B.

Because of the reasons discussed on page 49 of this report, the coefficients of storage obtained from the foregoing tests were not used in the quantitative computations. However, the coefficients did indicate that artesian conditions existed during the pumping tests.

### Water Levels

#### History of Water Levels

Very little is known about the water levels in the area prior to 1940. During the field work in the early 1940's, observation wells, were established in the area, and periodic measurements have been made since that time. As shown by the hydrographs (Fig. 7), the water levels remained approximately at the same level or trended slightly upward through the period 1940-52, then declined at a slow rate. After 1952, the effect of pumping for irrigation is reflected on the hydrographs and masks the effect of precipitation in the area.

Figure 7--Hydrographs of wells in the Grant-Stanton area.

Most of the water levels measured during and since 1957 have been in irrigation wells that obtain water from unconsolidated aquifers. These are gravel-walled wells which are perforated opposite all water-bearing materials penetrated in the well. Thus, these measurements are of the composite water levels for all the formations penetrated in each well (Tables 16, 17, 18).

Few wells in the area are perforated only in the sandstone aquifers. A few scattered wells were perforated both in the unconsolidated and the sandstone aquifers to the bottom of the Cheyenne Sandstone. The water levels in these wells, cased through the sandstone aquifers including the Cheyenne Sandstone, were compared with water levels in nearby wells screened only in the unconsolidated materials. The water levels in these two types of wells were at approximately the same level; hence, it was assumed that the 1960 water levels throughout the area were at approximately the same level in wells screened in both the unconsolidated and consolidated aquifers throughout the Cheyenne Sandstone. Little is known about the water levels in the Triassic sandstone, but they probably are comparable with those in the unconsolidated aquifers of the area. However, in northeastern Grant County, the flow in the Triassic sandstones is probably toward the east or northeast as compared with the southeasterly flow in the unconsolidated materials, and there may be some difference in water levels in this area.

During most years, pumping for irrigation causes considerable decline of water levels during the summer months, but some recovery of water levels is noted during the late winter and early spring months. An example of this is shown by fluctuations in well 28-38-8bc. Water levels in this well were as follows: during the late summer of 1959, 180 feet reported; March 21, 1960, 79.7 feet; and January 22, 1963, 110 feet. Pumping for irrigation in 1959 was mostly during the summer months, but in 1962, pumping was continued through December in addition to the summer months. The above well was not measured in 1962, but fluctuations in well 28-38-27ca can be used as an example. Water levels in this well were: March 30, 1960, 81.7 feet; Sept. 6, 1962, 150.7 feet; Oct. 11, 1962, 138.5 feet; Nov. 1, 1962, 123.6 feet; and Jan. 22, 1963, 103.7 feet.

Figure 8--Decline of water level in in the Grant-Stanton area.

The change in water levels in much of Grant and Stanton counties from about 1940 to Jan. 22, 1963, is shown in Figure 9. Figure 9 was prepared from Plate 11A which shows the water level as of 1939-42 and from an unpublished map which shows the water level for Jan. 22, 1963. Plate 11A was superimposed over the 1963 map and contours drawn through points of equal change. A map showing the change from about 1939-42 to March-April 1960 was given by Broeker and Fishel (1962, p. 31). If Figure 9 is compared with the acreage irrigated (Pl. 12), the close correlation between decline in water level and the areal distribution of pumping for irrigation may be noted.

Figure 9--Change of water level in Grant and Stanton counties from 1939-42 to January 22, 1963. A larger version of this figure is available.

The areal decline of water level from 1939-42 to 1960 and from 1939-42 to 1963 is shown graphically in Figure 8. The water level declined (1939-42 to 1963) 70 feet or more in an area of less than 1 square mile, 60 feet or more in 10 square miles, 40 feet or more in 174 square miles, 20 feet or more in 420 square miles, and 10 feet or more in 662 square miles.

### Withdrawals of Ground Water

by Carl E. Nuzman, Engineer,
Division of Water Resources,
Kansas State Board of Agriculture

The Geological Surveys' open file well records first reported the use of wells for irrigation in this area in 1940. As of that date, there were 4 irrigation wells in Stanton County and 8 in Grant County. The publication, "United States Census of Irrigation--Kansas 1940," listed 319 acres irrigated in Stanton County but did not mention Grant County. A report to the Governor of Kansas in 1944 listed 330 acres irrigated in Stanton County and 1,178 acres in Grant County. A report for 1948 by the Extension Service of Kansas State University listed 7,520 acres irrigated in Stanton County and 12,500 acres irrigated in Grant County. The Kansas Water Resources Board furnished reports of water usage for the period 1950 through 1957. The withdrawals for 1958 through 1960 (Table 6, 7) are compilations of the data furnished directly to the Division of Water Resources. In 1960 an estimated 68,000 acres were irrigated in Stanton County and 81,000 acres were irrigated in Grant County. The information obtained from the above sources is summarized in Figure 10, which demonstrates the growth of irrigation in the area.

An examination of the records indicates that in 1960 less than 4,000 acre-feet per year was pumped for municipal, rural, and industrial use. As this is less than 2 percent of the total use, or within the limit of error in estimation of irrigation use, only the irrigation use is shown in Figure 10 and Tables 6 and 7.

Table 6--Reported pumpage from irrigation wells (acre-feet) in Grant County, 1958-1960

Well number 1958 1959 1960
27-35-10cc 640 674 616
27-35-24ac   1,406
27-35-27ca 1,810 2,570 1,175
27-35-29ba   865 788
27-35-33bb   880 344

27-36-14cc     1,369
27-36-15dd
27-36-15cc   997 1,148
27-36-18dc 636 436 532
27-36-21dc
27-36-23dc
27-36-25aa   716
27-36-25cc 517 716

27-37-3bd
27-37-3dd
27-37-4ab
27-37-11ab   352 344
27-37-14ba   1,044 625
27-37-16bb 141 409 380
27-37-19db   716 1,363
27-37-20cd 684 1,249 1,326
27-37-25cb 811 402 459
27-37-26bc 392 1,231 1,194
27-37-28cb     186
27-37-29cb
27-37-29cc 772 1,190 1,274
27-37-30bd 681 955 1,243
27-37-33cc 263 394 398
27-37-34bc1
27-37-34da 257 292 454
27-37-35dc 456   168
27-37-36cc     302

27-38-1da 106   354
27-38-6cb   320
27-38-12dd 361   276
27-38-13ab 299   229
27-38-13cc 157 155 158
27-38-14cd 99 238 265
27-38-15bb 252 241 253
27-38-15da 88 292 353
27-38-19bc   270 967
27-38-19db   112
27-38-20bd   333
27-38-20cb   219
27-38-21cb
27-38-22cb   860 661
27-38-22cc   859 1,115
27-38-23ca   717 728
27-38-23cb2   587 317
27-38-24cc 532   666
27-38-25bb
27-38-26bb 367 516 545
27-38-27aa   1,032
27-38-27bb   251 332
27-38-28cb3 709 1,216 927
27-38-29ac 1,080   1,524
27-38-30ca   875 1,105
27-38-30cb     825
27-38-31ba   516
27-38-31dd2   826 1,261
27-38-32bb     1,524
27-38-32bc
27-38-32cc   405 545
27-38-33cb

28-35-5bc     566
28-35-5dc 666 662
28-35-6ba 1,420 1,199 1,192
28-35-8bb     1,335
28-35-9aa 994 1,290 551
28-35-10bb     182
28-35-15cb   267 305
28-35-20ab 870 985 905
28-35-21bb 445 691 395
28-35-22ac   336 258
28-35-22bb 363 398 407
28-35-23bd   325
28-35-27bb
28-35-27bc   940
28-35-29bc   1,326 1,237
28-35-30bb 811 624
28-35-31cd1     5
28-35-31cd2     61
28-35-35dc   994 690
28-35-36ab 476 649 759

28-36-2ba   420 492
28-36-2cd     420
28-36-11ba   625 1,095
28-36-13ac 254 744 423

28-37-2bb   182
28-37-2bc   177
28-37-4ac 122 269 244
28-37-6bb 374 239
28-37-7cb 134 428 530
28-37-9ac
28-37-9bb 363 444 613
28-37-9cc 272 431
28-37-10bc 412
28-37-17cb     848
28-37-20cd2     530
28-37-22ab   177
28-37-27cc1
28-37-27cc2 158
28-37-27cd   490
28-37-28dc 500 398 276
28-37-28dd1 200 155 94
28-37-28dd2 500 471 446
28-37-30bb   923 1,147
28-37-31aa1
28-37-31aa2   107 107

28-38-4bb   293
28-38-4cc   420
28-38-5ac   536
28-38-5bd   658 1,946
28-28-5dc 1,400 420
28-38-6bc
28-38-6cb
28-38-7ab 321 243
28-38-7bb
28-38-8bb2 1,236 1,503 1,095
28-38-8bc 348 265 203
28-38-9ca 795 1,105 1,050
28-38-9cb   6 7
28-38-10ab
28-38-10bb     1,247
28-38-12bc
28-38-12cb 308 864 1,166
28-38-15cb
28-38-16ab
28-38-16bb   928 176
28-38-16cb     407
28-38-16db1     231
28-38-16db3
28-38-17ab   828 1,574
28-38-17bb   608 1,193
28-38-17cb   862 1,432
28-38-18bb 1,079 1,538 1,263
28-38-18db
28-38-18dc   309 795
28-38-19bc 862 1,314 888
28-38-19bd 994 726 650
28-38-20dc1 495 840 322
28-38-20dc2   435 371
28-38-27ba
28-38-27ca   1,784 958
28-38-27cb
28-38-28da   1,200 1,505
28-38-30cb 640 159
28-38-30cc   482
28-38-31db 786   628
28-38-33ba2
28-38-33bd
28-38-35bc 663 942

29-35-6ba   490 582
29-35-7bc1
29-35-7bc2
29-35-7cb1
29-35-7cb2   422
29-35-12dd   130 141
29-35-13ac 868 835
29-35-15ab 561
29-35-24ba 817
29-35-24bc   2,298 1,390
29-35-25dc1
29-35-25dc2
29-35-25dc3
29-35-25dd2
29-35-25dd3   101

29-36-19bc
29-36-30bc     62
29-36-30dc
29-36-31db 269 221 316

29-37-8cb 362   636
29-37-19db   1,031 550
29-37-21bc   998
29-37-22aa
29-37-22cc2 610 949 486
29-37-26cc 823
29-37-28bb 132 707 321
29-37-28cb   919 687
29-37-29bb 561 497
29-37-32bd   577 450
29-37-32cc1     364
29-37-32db   390
29-37-34bd   486 318
29-37-35ac
29-37-35cc 566
29-37-35cd

29-38-1bb 790   954
29-38-1ca     530
29-38-3ba   960 1,467
29-38-4cc   531 550
29-38-5aab
29-38-5aac 406 403 430
29-38-7da   1,114 1,230
29-38-8cc 1,127   921
29-38-22bb   344 440
20-38-22cb 728 808 529
29-38-25ba 367 171 330
29-38-31dc
29-38-35ac2 68 212 143
9-9-38-35cd 126 180 744
29-38-35db 180 305 116

30-35-2db 118 308 210
30-35-19bc1 219 373 586

30-36-5bb2     5
30-36-5cb     55
30-36-6bb 693 370 397
30-36-6bd 491 440 375
30-36-7aa 45 379 643
30-36-7ab   176 595
30-36-7cb
30-36-8cd   512 338
30-36-9bb
30-36-9dc
30-36-16da1   270
30-36-32bb 736   254

30-37-1ab
30-37-2ba2 149   221
30-37-6dc
30-37-Scc   490 516
30-37-9cc     688
30-37-10ab
30-37-10bb2
30-37-10bb3 42 28 27
30-37-10dc 850   759
30-37-11db   1,202 1,166
30-37-15cb2     678
30-37-16da     543
30-37-17bc   1,259 644
30-37-19aa2   871
30-37-20cb 207 341
30-37-20cc   760
30-37-21bd   333 397
30-37-21cc 324 213 344
30-37-25dd2   331 292
30-37-26cc 66   221
30-37-26da
30-37-35bd 465 590 592
30-37-36bc 358 496 466

30-38-2ab
30-38-2cb 615 110
30-38-2cc
30-38-3dc 383 615 1,074
30-38-5bb   633 540
30-38-6bc   160
30-38-6cc   1,988
30-38-10ab 645 728 944
30-38-10bc     360
30-38-11bc3
30-38-11dd 236 210 230
30-38-12cc 964 1,062 1,155
30-38-13cc 1,237 1,011 1,363
30-38-14ac   1,114 1,224
30-38-15db   684 1,610
30-38-26da   914 660
30-38-30ac
30-38-34bc   1,170 575
30-38-35db     728
30-38-36bb

Totals 50,759 102,734 101,905

Table 7--Reported pumpage from irrigation wells (acre-feet) in Stanton County, 1958-1960

Well number 1958 1959 1960
27-39-13ac 274 468 493
27-39-21ac   1,415 980
27-39-22db 728
27-39-23ac2 376 525 462
27-39-23cc
27-39-25bb 939 900
27-39-25cb
27-39-26ab 130 275 265
27-39-26bc
27-39-26db
27-39-27bb 100 363 435
27-39-27cb 98 127 414
27-39-28ba 694 613
27-39-33bd
27-39-34cc     1,063
27-39-34dd 1,293 1,367
27-39-35ab
27-39-35cb     1,124

27-40-22da     4
27-40-25cb
27-40-26ba   795 552
27-40-35ab1
27-40-36ba   240

27-41-2db
21 41-10ac   619 618
27-41-31ac 919 768 715
27-41-31cc2   667 1,325
27-41-35cc 368 258 195

27-42-11db
27-42-31cc   178 276

28-39-1bb 560 545
28-39-1dd
28-39-2ab
28-39-2cb     615
28-39-2dc     662
28-39-3bb   933 880
28-39-5bb2
28-39-6dc     748
28-39-8ac     1,268
28-39-Sbb 243 843 1,213
28-39-8bc 257 948 1,386
28-39-8db
28-39-9ab   219 281
28-39-11aa
28-39-11bc     647
28-39-12ac
28-39-12bb
28-39-11bd
28-39-12cc
28-39-14bb2
28-39-15ac 663 661 644
28-39-16dc 400 1,051 1,035
28-39-17bc   610 692
28-39-17db     595
28-39-18bb 1,240 414 441
28-39-18bd 1,176 840 682
28-39-20ac   888 1,062
28-39-20bb 1,240 883
28-39-20bd
28-39-21cc     249
28-39-22ac 863 477 464
28-39-22db 456 517 707
28-39-23aa   392 331
28-39-23dd 381 354 456
28-39-24cc2
28-39-26ac 760   715
28-39-26cd 690 461 646
28-39-27bd     716
28-39-28ac     580
28-39-28cc     274
28-39-29cb     663
28-39-29cc     663
28-39-29cd     663
28-39-30cc 1,240 886
28-39-3tab 704 970
28-39-31bc 520 424
28-39-31cc   298
28-39-33dc   640 690
28-39-36ab   676

28-40-2ab
28-40-2cb   1,262 830
28-40-3ab   221
28-40-3cb
28-40-3cc
28-40-4cc   618 259
28-40-9ac   250 251
28-40-15cc 524 613 680
28-40-17cb     532
28-40-19dc
28-40-20bc
28-40-21cc 666 738 954
28-40-23ac   632 499
28-40-25cc2
28-40-25dc
28-40-26bc   1,326
28-40-27cc 884 795 884
28-40-28cb   1,031
28-40-29ab   1,053
28-40-29bc 688 919 783
28-40-30cb 662
28-40-31bb   1,312
28-40-32bd 530 634 602
28-40-32cc 1,000
28-40-36cb   866

28-41-5bb   943
18-41-6ab   950 894
28-41-11bc 948 1,497
28-41-12bb   398
28-41-14aa   882
28-41-19dc 384   876
28-41-25ab
28-41-31bd 151 191 381
28-41-36db 180 204 537
28-41-36dc
28-41-36dd   2 2

28-42-6db   109
28-42-8cc 109 1
28-42-14bc     711
28-42-16cd1   442
28-42-16cd2   795
28-42-16dc   637
28-42-20dd
28-42-21ab   461
28-42-22ba 1,034 892
28-42-23db 837 872
28-42-24dc
28-42-25aa
28-42-26aa 257 563
28-42-32bb 46   9
28-42-35ba
28-42-35bb

29-39-1bb
29-39-2dc
29-39-6bc   1,197 1,577
29-39-6cc 779 1,195
29-39-8ac 537   1,186
29-39-9dd2   785
29-39-10cc
29-39-11ac
29-39-15ac 370 749
29-39-15bb   732 699
29-39-17bc     1,365
29-39-18ac
29-39-20bc
29-39-21db   371 371
29-39-24dd 410 421 237
29-39-26bd 335 305 729
29-39-27cc

29-40-1cc 682 1,304
29-40-3bc   416 704
29-40-3db
29-40-4cd 364   362
29-40-6db 277 858
29-40-11bb 962 816 1,197
29-40-11cb 913 958 1,001
29-40-12bb 640 1,447
29-40-15db   596 927
29-40-16ba   265 132
29-40-25dc 371 446 224
29-40-26bb   345 689
29-40-31db 276
29-40-33ac 419 204 289
29-40-34bb 392 333 535
29-40-35dd   286 545
29-41-3da
29-41-11bd   147
29-41-13ac   400 1,259
29-41-23db 398 199 93
29-41-24ac
29-41-31cb   71

29-42-8cd 378 401 378
29-42-11dc   13
29-42-24cc     20

29-43-3db

30-39-2ab 873 724 721
30-39-2bb   529 430
30-39-2cb 900 777
30-39-4dc
30-39-12cc
30-39-13cb 1,299 1,140 1,286
30-39-18bb 1,000 1,389 604
30-39-20da 506   915
30-39-22ac 507 520 1,054
30-39-23bb 625 626 644
30-39-23cb 736 357 589
30-39-32da 475 619 636
30-39-36bd   803 914

30-40-2cb
30-40-5ca 722
30-40-8ab 262
30-40-9dc 266
30-40-22cb
30-40-24cc1 72
30-40-24cc2
30-40-24cd
30-40-25dc 378
30-40-27ac
30-40-33cc
30-40-34ac
30-40-35bb
30-40-36ac     18

30-41-13cc

30-42-12ac   119
30-42-16bd 125 254 395

30-43-26dd 1,183 1,342 1,213
30-43-27cc 634 619 972
30-43-28ab 74 110 88
30-43-28dd 398 465
30-43-29a   238
30-43-34bb 184 198
30-43-35bb 1,100 1,738 2,210
Totals 47, 034 74,444 66,481

Figure 10--Irrigation growth and withdrawals of ground water in the Grant-Stanton area. (Prepared by Carl Nuzman.)

In 1958, those water users in Grant County who reported used 72 percent of their authorized appropriation. Thus, if the total authorized for Grant County was 158,300 acre-feet, 72 percent of this value or 114,000 acre-feet was the estimated water pumped (Fig. 10). In 1959, 81 percent of the authorized amount of 167,000 acre-feet was reported, and 135,000 acre-feet was the estimated total used. In 1960 the estimated quantity used was 131,000 acre-feet.

In Stanton County irrigators reported the use of 72 percent of their authorized quantity in 1958 and 80 percent in 1959. Thus, the estimated total used in Stanton County was 91,000 acre-feet in 1958 and 113,000 acre-feet in 1959. In 1960, the estimated quantity used was 128,000 acre-feet.

The differences between Tables 6 and 7 and Figure 10 are due to the differences in reported pumpage and actual use. The acreage for which applications for water rights have been filed with the Division of Water Resources and the location of irrigation wells are shown on Plate 12.

### Perched Zones of Saturation

There are several perched zones of saturation in the area. The northwest quarter of Grant County and part of Stanton County contains a perched zone. The water level in wells screened in the perched zone is generally 50 to 65 feet below the land surface. The zone is intercepted by the Lakin Draw and several seeps discharge at the bottom of the draw during prolonged wet periods.

Two perched zones are above the major aquifer in the Hickok area. Water levels in wells about 130 feet deep are 85 feet below the land surface. Another thin aquifer occurs between 150 and 200 feet below the surface in the Hickok area. The water level is not known but probably is near 130 feet. The principal aquifer is about 20 feet thick and is from 350 to 370 feet below the surface. The water level associated with this aquifer is near 182 feet.

Another perched zone is present along the Cimarron River south of Ulysses. Little is known about the water levels in this area, but springs discharge along the river bottom during wet periods. Wagon Bed Springs is in this area but is dry most of the time.

The water level in the small gravel-filled valley in the southwest corner of Stanton County stands slightly above that in wells screened in the underlying sandstone aquifers. Local well drillers are careful not to penetrate the thin clay layer separating the two aquifers when drilling shallow wells, as the water in the shallow aquifer will drain into the sandstone. Irrigation wells screened in the shallow aquifer are reported to yield as much as 3,000 gallons per minute.

### Water-Level Contour Maps and their Analysis

Water-level contour maps were prepared for the water levels measured during the periods: 1939-42 (Pl. 11A); the winter of 1957-58 (Pl. 11B); the spring of 1959 (Pl. 11C); October 1959 (Pl. 12); the spring of 1960 (Pl. 11D); and Jan. 22, 1963 (unpublished). Water levels were measured in about 270 wells. These maps show water levels in the aquifers tapped by nearly all the irrigation wells in Grant and Stanton counties, but excludes any of the perched zones discussed above. [The datum is mean sea level, and the contours join points of equal altitude on the piezometric surface (pressure head or water level) at the time of measurement.]

Water-level contour maps indicate water levels with respect to a known datum, the direction of ground-water movement, areas of recharge and discharge, and the effects of pumping. They can be used with other hydrologic data to compute the rate of movement of water, and successive maps can be used to compute changes in ground-water storage. A practical use of the maps is in determine the depth to water below the land surface in any locality if the altitude of the land surface is known. For example, the depth to water below land surface, 163 feet, is the difference between the altitude of the land surface at Johnson (about 3,342 feet above sea level) and the altitude of the water surface (about 3,179 feet) shown on the 1939-42 map.

#### Computation of Flow

Ground water moves at right angles to the water-level contours or from areas of high to low head. The water-level contour maps indicate that the movement of water in the area is predominantly eastward. Most of the ground water enters Stanton County from the west through the unconsolidated and sandstone aquifers, then flows eastward through Stanton and Grant counties into southwestern Haskell County. Some water enters the two-county area from Morton, Stevens, Hamilton, and southwestern Kearny counties, and more enters northeastern Grant County from Kearny County.

The quantity of flow eastward can be computed from the contour maps by application of the formula

Q = TIL

where: Q is the quantity of water flowing per unit of time,
T is the transmissibility, as previously defined,
I is the hydraulic gradient obtained from the contour map, and
L is the length of the segment through which the water moves, measured normal to the direction of flow.

The quantity of ground-water flow was computed for the 1939-42 water-level contour map (Pl. 11A) and summarized in Table 8. To make these computations, the following assumptions were made:

1. The water level was static during the period, and no water was removed from or added to storage in the aquifers.
2. Pumpage was negligible and did not influence the shape of the water-level contours at the segments used for computations.
3. Sufficient data were collected on the hydrologic properties of the unconsolidated aquifers so that the calculations made are in the right order of magnitude.
4. Any increase in quantity of flow between the contours used for the computation was from the sandstone aquifers that are in contact with the unconsolidated aquifers in the subsurface or from recharge by precipitation.
5. The lateral boundaries, ADGJM and CFILN, are drawn perpendicular to the contour lines on Plate 11A, showing that no water flows across these boundaries.

Using these assumptions, the northernmost segment of flow across the 3,240-foot contour in northwestern Stanton County was computed. As an example, the coefficient of transmissibility in that area is 90,000 gpd/ft, from Plate 11B. The hydraulic gradient (1) averages 10.7 feet per mile between the 3,230- and 3,250-foot contours on Plate 11A, normal to the direction of flow. Thus: Q = 90,000 X 10.7 X 1.58 = 1.54 mgd. The flow across the rest of the 3,240-foot contour was computed in this way, as was the flow across the 3,160-, 3,090-, 3,000-, and 2,830-foot contours. The results of these computations were tabulated in Table 8, along with an estimate of the flow through the underlying sandstones.

Data available on the water levels and hydrologic properties of the sandstone aquifers were insufficient to make more than an estimate of the flow through the sandstones.

Table 8--Summary of ground-water flow eastward across Grant and Stanton counties (in million gallons per day), 1939-42. (1. Segments A to M and C to N shown on Plate 11A; Npl, Pleistocene deposits; No, Ogallala Formation; SS, sandstone in pre-Pliocene rocks.)

Contour Flow into area from Calculated
flow
in Npl
and No
Increase in Npl
and No from
Estimated
flow in SS
aquifers
Total flow
Npl, No
and SS
aquifers
sandstone rainfall
3240Colorado and western Stanton County (A-C) 20.8  30.0
Southwestern Hamilton County1.5  2.0
Northwestern Morton County1.5  2.0
sub-totals23.8  34.057.8
3160Colorado and western Stanton County (D-F)23.31.31.229.7
Southwestern Hamilton County3.0  3.9
Northwestern Morton County1.2  3.4
sub-totals27.5  37.064.5
Southern Hamilton County1.1  3.5
Northern Morton and southern Stanton Counties9.8  3.4
sub-totals38.6  34.573.1
3000Colorado, Stanton and western Grant Counties (J-L)30.91.12.024.5
Southern Hamilton and Kearny Counties2.3  2.3
Northern Morton and southern Stanton and Grant Counties6.5  0.5
sub-totals39.7  27.367.0
2830Colorado, Grant and Stanton Counties (M-N)35.22.12.222.8
Southern Hamilton and Kearny Counties5.9  2.3
Southern Kearny County (Arkansas River valley?)8.9
Northern Morton and Stevens Counties11.2
sub-totals61.2  25.186.3

Recharge from Precipitation

As the water flowed eastward through the unconsolidated aquifers, the flow increased about 14 mgd between the 3,240- and the 2,830-foot contours and within the boundaries of ADGJM and CFILN (Pl. 11A). Some of this increase was from the sandstone aquifers that are in contact in the subsurface, and some was from precipitation within the area. The area DEKJ (Pl. 11A) was selected to make an estimate of the recharge from precipitation because the sandstones were not in contact in the subsurface and did not increase the eastward flow within this area. The inflow across the 3,160-foot contour and between points D and E was 13 mgd. The outflow across the 3,000-foot contour between the points J and K was 15 mgd. Assuming that this increase of 2.0 mgd is all from precipitation in the area of 160 square miles, the, recharge rate was about 0.013 mgd/sq. mi. or about 0.3 inch per year, which is about 2 percent of the annual precipitation. This recharge rate was applied to the rest of the area, and the recharge from precipitation was separated from the flow contributed to the unconsolidated aquifers by the sandstones.

Small amounts of water seep from Bear Creek into the ground-water reservoir throughout the year in western Stanton County. During flood stages the stream is believed to contribute large amounts of its flow to ground water throughout its total reach. However, these floods occur only at about 10-year intervals, and the total area flooded is less than 10 percent of the combined areas of Grant and Stanton counties.

#### Summary of Flow

Plate 11A and Table 8 indicate that about 58 mgd was flowing eastward into the area from Colorado and southwestern Hamilton and northwestern Morton counties. About 24 mgd flows through the unconsolidated aquifers and 34 mgd flows through the sandstone aquifers. As this water moves eastward, some of the flow is transferred from the sandstone aquifers to the unconsolidated aquifers. If the amount of 0.013 mgd/sq. mi. as calculated for the recharge from precipitation is correct, then the total recharge from precipitation within the AMNC polygon (an area of 530 sq. mi.) was about 7 mgd. The remaining increase of 7 mgd in the unconsolidated aquifers and within the polygon was assumed to be contributed by the sandstone aquifers. There is some doubt that the recharge is uniformly distributed over the area as assumed above. The recharge may be confined to gravel or sand areas of the streams and their flood plains. If this is true, the recharge within the AMNC polygon would be less than 7 mgd and the increase from the sandstone aquifers would be between 7 and 14 mgd.

The outflow of 86 mgd across the 2,830-foot contour and the eastern Grant County line north of the 2,830-foot contour in eastern Grant County includes 61 mgd flowing eastward in the unconsolidated aquifers and about 25 mgd flowing in the sandstone aquifers. About 58 mgd of this was continuous flow from the most westerly areas of Stanton County, 13 mgd possibly was recharge from precipitation within the area east of the 3,240 contour (977 square miles), 6 mgd was lateral inflow from the adjacent counties to the north and south, and 9 mgd was the flow southeastward from eastern Kearny County across the northeast corner of Grant County. The 9 mgd probably is inflow from the Arkansas River drainage.

The foregoing analyses were made on the 1939-42 map because pumping in the area was negligible at that time and thus had very little effect on the shape of the water-level contours. Pumping in the area since that time has caused considerable decline of the water levels near the center of the area. However, the 1939-42 and 1960 maps indicate that there has been very little change in the hydraulic gradients across the 3,240- and 2,830-foot contours, and the water-level near these contours has not changed appreciably. Thus it may be assumed that T, I, and L have not changed appreciably, and the flow into and out of the area was approximately the same in 1960 as in 1939-42. As the saturated thickness (and consequently I) is reduced in the future and I changes, the flow into and out of the area will also change.

On Jan. 22, 1963, the water-level contours in the outflow area had changed slightly, but the inflow was estimated to be about the same as in 1939-42. Pumping in the outflow area within a month of the time of measurements on Jan. 22, 1963, had changed the hydraulic gradients so that an outflow comparable to 1939-42 could not be computed. The saturated thickness had been reduced about 2 percent and thus the outflow was probably reduced also by at least 2 percent.

### Reduction in Storage of Ground Water

#### Weighted-Average Water Level

The withdrawal of ground-water throughout the years has caused a decline of water level in the area, and in some areas concentrated pumping has caused considerable decline. In order to determine the average decline for the period 1939-42 to 1960, a weighted-average water level was computed from all the water-level contour maps, except the 1957-58 maps (the 1957-58 map was incomplete for part of the area). To compute the weighted-average, the volume of the ground-water reservoir between the highest and lowest water-level contours was computed for each map by use of the trapezoidal formula as adapted from Fader (1957, p. 5):

Vt = h [1/2 (A0 + An) + A1 + A2 + A3 + . . . + An-1]

in which: Vt is the volume between the highest and lowest contour,
h is the contour interval in feet,
A0 is the area in square miles embraced by the initial or highest contour,
A1, A2 . . . are the areas embraced by the next successive lower contours in square miles,
An is the area embraced by the lowest contour in square miles (Fig. 11). A sketch showing the symbols used in the computation of the weighted-average water level is shown in Figure 11.

Figure 11--Block diagram illustrating symbols used in computation of weighted-average water level.

The areas for each contour were obtained by a planimeter and are given in Table 9 for the 1939-42 map as an example. Substituting the values in the above formula and simplifying:

Vt = 10 [(977 / 2) + 24,858] = 253,480 square-miles-feet

Dividing this figure by the total planimetered area of 977 square miles, the result is 259.4 feet, which is the weighted-average water level above the 2,780-foot contour. Thus, the altitude of the weighted-average water level computed by this method was:

 1939-42 3,039 ft. Spring, 1959 3,031 ft. Fall, 1959 3,028 ft. Spring, 1960 3,031 ft. January 22, 1960 3,021 ft.

This is a drop of 8 feet between 1939-42 and spring 1960, most of which probably occurred after 1955. The weighted-average declined 10 feet between spring 1960 and January 1963 or an average of 3 feet per year.

Table 9--Areas used in computation of weighted-average water level, 1939-42.

Contour A Area, square miles
A0 + An A1 + A2 + ...
3,240A00
3,230A1 18.8
3,220A2 37.7
3,210A3 57.1
3,200A4 79.2
3,190A5 103.5
3,180A6 127.1
3,170A7 154.7
3,160A8 189.8
3,150A9 229.9
3,140A10 262.7
3,130A11 292.8
3,120A12 321.5
3,110A13 349.3
3,100A14 374.8
3,090A15 405.2
3,080A16 434.9
3,070A17 460.9
3,060A18 486.5
3,050A19 509.2
3,040A20 532.3
3,030A21 554.5
3,020A22 574.0
3,010A23 593.5
3,000A24 612.7
3,090A25 631.5
3,080A26 650.3
3,070A27 670.7
3,060A28 688.5
3,050A29 705.9
3,040A30 727.5
3,030A31 747.8
3,020A32 766.1
3,010A33 786.2
2,900A34 806.3
2,890A35 826.5
2,880A36 844.5
2,870A37 861.2
2,860A38 877.5
2,850A39 891.6
2,840A40 904.4
2,830A41 917.0
2,820A42 928.2
2,810A43 940.6
2,800A44 951.9
2,790A45 970.8
2,780A46976.8
Totals976.824,858.0

The areas considered in the above computations included all of both counties east of the 3,240-foot contour on Plate 11A. This 3,240-foot contour was plotted on subsequent maps so that the same area was compared each time. These boundaries were chosen because of their geographic convenience, because detailed water-level data were not collected outside these boundaries, and because water-level decline due to pumping was approximately zero in 1960 at these boundaries on all the maps. If these conditions were strictly true and the water levels could all be measured on the same day, the weighted-average water level should not have risen between the spring of 1959 and spring of 1960. The reason that the spring 1959 average was lower is that most of the later levels in the area of concentrated pumping in northwestern Grant County were measured in February, whereas the levels in the rest of the area were measured in late April and early May. Therefore, the water had time to move into the area of concentrated pumping, and the water levels outside the area of concentrated pumping consequently were lowered, resulting in a slightly low weighted-average. If weather and pumping conditions had allowed all the measurements to be made at one time, the spring 1959 weighted-average probably would have been about 0.5 foot above that for the spring 1960.

#### Computation of Areal Drawdown Coefficient

The highest coefficient of storage (S) obtained from the aquifer tests (Table 8) was 0.059. The value of S for the remainder of the tests was 0.01 or less. The longest test was for 2 weeks, and, hence, the silt, fine sand, and clay in the overlying aquicludes had a relatively short time to drain during the test compared with the 10 to 20 years since pumping started in the area. Therefore, an areal drawdown coefficient was computed for the period 1939-42 to 1960. The areal drawdown coefficient is here defined as the ratio of the quantity of water pumped in the area, in feet, to the decline of the weighted-averaged water level, in feet, during the period of removal. The areal drawdown coefficient might be called a "long term" coefficient of storage in places where the water is removed from within an area bounded by a zero drawdown contour (the lateral boundaries are at zero drawdown) and if corrected for recharge and discharge, should approach the specific yield of the materials being dewatered. Where part of the water is being removed from storage outside the area being considered, the areal drawdown coefficient will be larger than for the total area.

From 1939 through 1959, the weighted-average water level declined 8 feet (page 48). The quantity of water pumped during the 20-year period was estimated from Figure 10 to be about 1,620,000 acre-feet for the total area of Grant and Stanton counties. About 5 percent, or 87,000 acre-feet, of the pumping took place west of the area for which the decline of water level was computed. Therefore, the total pumpage was reduced to 1,540,000 acre-feet for the area considered. This withdrawal was then reduced to feet of water by dividing by the area, as follows:

1,540,000 acre-feet / (977 X 640 acres) = 2.47 feet.

The areal drawdown coefficient then would be 2.47/8 or 0.31.

The above areal drawdown coefficient can be further adjusted to approach the specific yield by correcting for recharge by precipitation over the 20-year period and for possible over-reporting of the pumpage. Assuming that the recharge rate of 0.013 mgd / sq. mi. (page 46) is correct, the recharge over the 977 square miles should be 0.013 X 20 X 977 X 365 X 3.07 = 280,000 acre-feet. This recharge was subtracted from the total pumpage and compared with the weighted-average decline as follows:

1,260,000 acre-feet / (977 X 640 acres) = 2.01 feet.

The areal drawdown coefficient adjusted for recharge from precipitation would be 2.01/8 or 0.25.

State and Federal personnel working on water resources of southwestern Kansas are of the opinion that pumping rates reported by irrigators are maximum rates rather than the rate actually used. Although there are insufficient data at present to determine the amount of over-reporting, it is estimated to be as much as 20 percent which would reduce the areal drawdown coefficient to 0.20 (adjusted for recharge from precipitation and estimated over-reported pumpage).

#### Future Water-Level Decline

The areal drawdown coefficient was computed for the purpose of estimating future water-level decline. Because the rate of annual withdrawal is unpredictable, estimates of future declines were not attempted. The weighted-average water level for the area east of the 3,240-foot contour on Plate 11A declined 8 feet between 1955 and 1960 (see page 48) and 10 feet between 1960 and 1963. It can be assumed that the weighted-average will decline considerably in the future if the present high rate of withdrawal continues. Because the weighted-averaged water level is an average, 8 or 10 feet decline would not be expected in all areas and some areas of high withdrawals will have more decline than other areas of low withdrawals, as shown on Figure 9. Well owners may obtain past declines for their individual well sites from Figure 9 and estimate future declines for their own use.

### Availability of Ground Water

#### Water in Storage

The saturated water-bearing materials in the Neogene deposits in Grant and Stanton counties range in thickness from 0 to more than 400 feet (Fig. 12). The contour line in Figure 12, showing zero thickness, represents the line of contact where the water table passes from the Pliocene or Pleistocene deposits into the underlying Cretaceous rocks.

Figure 12--Saturated thickness of Neogene deposits, Grant and Stanton counties, 1939-1942. A larger version of this figure is available.

In Grant and Stanton counties there are approximately 39 million acre-feet of water in storage between the water table and the base of the unconsolidated aquifers. There is probably another 16 million acre-feet in the sandstone below. These estimates are based on a coefficient of storage of 0.20, the total thickness of the saturated materials in the unconsolidated aquifers, and the thickness of the sandstone in the consolidated aquifers. The volume of the unconsolidated materials was measured by planimetering the spring 1960 water-level contour and the bedrock contour maps (Pl. 2A and 11D). The weighted-average altitude was computed for each map and the difference multiplied by the total area to obtain the volume of the unconsolidated material. The volume of water in the sandstones was estimated on the meager information available from electric and radioactivity logs of oil tests, a few geologic test holes, and six drillers' logs.

Not all the water in the unconsolidated aquifers is available for irrigation. As the water table declines, the yields of the wells will decline, and a time will be reached when the yields are no longer adequate for irrigation, but the yields may continue to be adequate for stock, domestic, or other uses.

#### Quantities Available

Because the sand and gravel beds are thin or practically absent in small areas, water is not available in sufficient quantity for irrigation throughout the whole area. The figures in parentheses on Plate 11B can be used as a rough guide to the availability of water. These figures are coefficients of transmissibility in thousands of gallons a day per foot. An approximate yield of a well in gallons a minute can be obtained by dividing the transmissibility by 100. Plate 11B shows the coefficient of transmissibility divided by 1,000. The values shown on Plate 11B should be multiplied by 10 to obtain the approximate gallons per minute. Because these data are general over large areas, this method of estimating yields should be used with extreme caution. Also the local well drillers should be consulted and test holes should be drilled before installation of any irrigation well.

Near Manter, in western Stanton County, the irrigation wells obtain their entire supply from the sandstone aquifers (see tables of well records). Most of the domestic and stock wells in western Stanton County are screened in sandstone aquifers. In the northern half of both Stanton and Grant counties and as far east as Ulysses, several irrigation wells are perforated in both the unconsolidated and sandstone aquifers. The meager information available on the sandstone aquifers is given in Table 2 and plotted on Plate 11C. These figures are plotted on the map as a guide for future test drilling in the area.

### Chemical Quality of Water

The chemical character of the water is indicated by 89 complete and 205 partial analyses of water collected from wells in the Grant-Stanton area. The analyses (Table 11 and Table 12) were made by the Sanitary Engineering Laboratory of the Kansas State Department of Health. The analyses in Table 13 and Table 14 were made in the field by the authors. The results of the analyses are given in parts per million, and the factors for converting parts per million of mineral constituents to equivalents per million are given in Table 10.

Table 10--Factors for converting parts per million of mineral constituents to equivalents per million.

Cation Conversionfactor Anion Conversionfactor Ca++ 0.04990 HCO3- .01639 Mg++ .08226 SO4- .02082 NA+ .04350 Cl- .02821 NO3- .01613 F- .05264

The dissolved solids in water samples from the Grant-Stanton area ranged from 169 ppm in well 27-35-16dd in the sand-hill area of northeastern Grant County to 1,470 ppm in shallow well 29-38-27aa1 along the North Cimarron River, southwest of Ulysses. Both of these water samples are from Pleistocene deposits. The average dissolved-solids content of water from the Pleistocene deposits was 439 ppm. The total hardness of water from the Pleistocene deposits ranged from 142 ppm in well 28-42-32dd to 809 ppm in well 27-38-20ad.

The dissolved solids in water from wells screened both in the Pleistocene and Pliocene deposits ranged from 185 ppm in well 27-35-24ac in northeastern Grant County to 790 ppm in well 28-30-4cc in northwestern Grant County. The average for the multiple-screened wells is about 389 ppm. The total hardness ranged from 148 ppm in well 27-35-24ac to 460 ppm in well 27-38-4cc. The average total hardness was 238 ppm.

The dissolved solids in water from wells screened in the Pliocene deposits ranged from 253 ppm in well 28-43-12bb in western Stanton County to 515 ppm in well 27-39-13bda in northeastern Stanton County. The average was 303 ppm. The total hardness ranged from 181 ppm in well 28-43-12bb to 246 ppm in well 27-39-13bda. The average was 198 ppm. Comparison of the hardness of water from Pliocene and Pleistocene aquifers indicates that water from Pliocene deposits generally is softer.

In water from the sandstone aquifers the dissolved solids ranged from 232 ppm in well 27-40-1cd to 622 ppm in well 27-39-13ac. The average from the sandstones is 371 ppm. The total hardness ranges from 176 ppm in well 39-41-33db to 360 ppm in well 27-39-13ad. The average for the sandstone aquifers was 244 ppm.

The water in the Pleistocene deposits of northeastern Grant County is somewhat softer and contains less dissolved solids than water from the rest of the area. This indicates recharge from precipitation in the sand hills of the area over a long period of years. The samples were not studied in detail for possible movement between aquifers.

#### Chemical Constituents in Relation to Irrigation

The suitability of water for irrigation can be determined by methods outlined in Agricultural Handbook 60 of the U. S. Department of Agriculture (U. S. Salinity Laboratory Staff, 1954).

Soil that was originally nonsaline and nonalkaline may become unproductive if excessive soluble salts or exchangeable sodium are allowed to accumulate because of improper irrigation and soil-management practices or inadequate drainage. If the amount of water applied to the soil is not in excess of the amount needed by plants, water will not percolate downward below the root zone, and mineral matter will accumulate at that depth. Likewise, impermeable soil zones near the surface can retard the downward movement of water and cause waterlogging of the soil and consequent deposition of salts.

The characteristics of irrigation water that seem to be most important in determining its usability are the total concentration of soluble salts and the relative activity of sodium ions in exchange reactions. For diagnosis and classification, the total concentration of soluble salts can be expressed in terms of electrical conductivity, which is a measure of the ability of inorganic salts in solution to conduct an electrical current. The electrical conductivity can be determined accurately in the laboratory, or approximately, by multiplying the total equivalents per million of calcium, magnesium, sodium, and potassium by 100, or by dividing the parts per million of total dissolved solids by 0.64 (U. S. Salinity Laboratory Staff, 1954, p. 69). Water having an electrical conductivity of less than 750 micromhos per centimeter (μmho/cm) is generally satisfactory for irrigation insofar as the salt content is concerned, although salt-sensitive crops such as strawberries, green beans, and red clover may be adversely affected by water having a conductivity of more than 250 μmho/cm. Water having conductivity in the range of 750 to 2,250 is widely used, and satisfactory crop growth is obtained under good management and favorable drainage, but saline soil will develop if leaching and drainage are inadequate. Water having a conductivity of about 2,250 μmho/cm has seldom been used successfully.

The sodium-adsorption ratio (SAR) of water, which relates to the adsorption of sodium by soil, may be determined by the formula

in which the ionic concentrations are expressed in equivalents per million. The SAR may be determined also by use of the nomogram shown in Figure 13. In it, the concentration of sodium expressed in equivalents per million is plotted on the left-hand scale, A, and the concentration of calcium plus magnesium, expressed in equivalents per million, is plotted on the right-hand scale, B. The point at which a line connecting these two points intersects the SAR scale, C, determines the SAR of the water. When the SAR and the electrical conductivity of a water are known, the suitability of water for irrigation can be determined by plotting the values on the nomogram. Table 15 lists the SAR of the 8 water samples plotted on Figures 13 and 14.

Figure 13--Nomogram for determining sodium-adsorption ratio of water. (See Table 15 for well numbers.)

Figure 14--Classification of irrigation waters from representative wells in the Grant-Stanton area. (See Table 15 for well numbers.)

Table 15--Index numbers of samples shown in Figures 13 and 14 and sodium adsorption ratio (SAR).

Well number Number used in
Figures 13 and 14
Geologic Source1 SAR
27-35-24ac1Npl, No0.3
27-39-13ac2Kd, Kc1.3
28-38- 4cc3Npl, No1.7
29-35-15ab4Npl1.3
29-36-23ddd5Npl3.1
29-36-30bc6Npl, No1.3
29-42-Ildc7Kd, Kc, TRd1.6
30-37-36bc8Npl1.0
1. Npl, Pleistocene; No, Ogallala Formation; Kd, Dakota Formation;
Kc, Cheyenne Sandstone; TRd, Dockum Group.

Low-sodium water (S1) (Fig. 14) can be used for irrigation on almost all soils with little danger of developing harmful levels of exchangeable sodium. Medium-sodium water (S2) can be used safely on coarse-textured or organic soils having good permeability, but it will present appreciable sodium hazard in certain fine-textured soils, especially those not leached thoroughly. High-sodium water (S3) may produce harmful levels of exchangeable sodium in most soils and will require special soil management, such as good drainage, thorough leaching, and addition of organic matter. Very high sodium water (S4) is generally unsatisfactory for irrigation unless special action is taken, such as addition of gypsum to the soil.

Low-salinity water (C1) can be used for irrigation of most crops on most soils with little likelihood that soil salinity will develop. Medium-salinity water (C2) can be used if a moderate amount of leaching occurs. Crops of moderate salt tolerance, such as potatoes, corn, wheat, oats, and alfalfa can be irrigated with C2 water without special practices. High-salinity water (C3) cannot be used on soils with restricted drainage. Very high salinity water (C4) can be used only on certain crops and then only if special practices are followed.

The irrigation water being used in the area is a low-sodium water, (Fig. 14) but it is medium to high in salinity.

### Phreatophytes

A plant that habitually obtains its water supply from the zone of saturation, either directly or through the capillary fringe, is termed a phreatophyte (Meinzer, 1923, p. 55). The Subcommittee on Phreatophytes (1958, p. 5,) states, "A phreatophyte in most cases is a mesophyte which grows in arid or semi-arid climates and which gets its water supply from ground water." The most abundant phreatophytes in this area are salt cedar (five-stamen tamarisk), willows, and cottonwoods. In some parts of the west these plants grow along valleys and flood plains and use considerable water. These plants, the tamarisk in particular, are of little or no economic value and grow thick enough in some areas to choke the stream channels, causing flooding. The tamarisk is difficult to control once growth has started, and care should be taken not to spread this plant deliberately.

Tamarisks, willows, and cottonwoods grow in abundance along the Arkansas River as far east as Dodge City, Kansas. It is not known how far they extend down the Cimarron River, but a few grow near Wagon Bed Springs south of Ulysses. Figure 15 shows the areas where tamarisks are growing in the Grant-Stanton area.

Figure 15--Map showing occurrence of phreatophytes in the Grant-Stanton area. (Areas of phreatophytes shown in black and indicated by arrows.) A larger version of this figure is available.

Kansas Geological Survey, Geology
Placed on web July 23, 2007; originally published December 1964.