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Introduction
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Hydrology
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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
27-36-15dd	Npl, No	153,000	0.00014
27-37-29cc	Npl, No	52,100	.00012 (b)
27-38-15da	Npl, No	63,400	.00023 (b)
27-38-19cd	Npl, No	590,000	.0048
27-38-22cb	Npl, No	159,000	.00035
27-38-23ca	Npl, No	71,000	.00021
27-38-32bb	Npl, No	188,000	.0024
28-36-11ba	Npl, No	215,000	.00022
28-38-12cb	Npl, No	50,600	.00028
28-38-15cb	Npl, No	119,000	.00060
28-38-27ba	Npl, No	125,000	.00021
29-35-15ab	Npl	134,000	.00038 (b)
29-38-35db	Npl, No	45,000	.00094 (b)
30-37-2ba2	Npl, No	29,600	.00014 (b)
30-37-19aa2	Npl	56,000	.00029 (b)
30-37-26da	Npl, No	145,000	.0032
30-38-30ac	Npl, No	337,000	.00044 (c)
Stanton County
27-39-13ac	Kd, Kc	45,800
27-40-25cb	Npl, No	137,000	.0048
28-39-12ac	Npl	40,500	.00011
28-39-20bd	Npl, No	188,000	.00095
28-39-24cc2	Npl, No	465,000	.0094
28-41-14aa	Npl, No	352,000	.059
29-39-24dd	Npl, No	58,000	.0011 (b)
30-40-24cd	Npl, No, Kd	97,500	.0013
30-41-13cc	No, Kd	137,000	.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
27-35-17ad		810	432
27-35-24ac		1,406
27-35-27ca	1,810	2,570	1,175
27-35-29ba		865	788
27-35-33bb		880	344
27-36-13ad	804	240
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
27-38-12ad
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
-99-38-27ad	380	456	474
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
27-39-27ad1
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
3240	Colorado and western Stanton County (A-C)	20.8			30.0
	Southwestern Hamilton County	1.5			2.0
	Northwestern Morton County	1.5			2.0
	sub-totals	23.8			34.0	57.8
3160	Colorado and western Stanton County (D-F)	23.3	1.3	1.2	29.7
	Southwestern Hamilton County	3.0			3.9
	Northwestern Morton County	1.2			3.4
	sub-totals	27.5			37.0	64.5
3090	Colorado and Stanton County (G-I)	27.8	2.5	2.0	27.6
	Southern Hamilton County	1.1			3.5
	Northern Morton and southern Stanton Counties	9.8			3.4
	sub-totals	38.6			34.5	73.1
3000	Colorado, Stanton and western Grant Counties (J-L)	30.9	1.1	2.0	24.5
	Southern Hamilton and Kearny Counties	2.3			2.3
	Northern Morton and southern Stanton and Grant Counties	6.5			0.5
	sub-totals	39.7			27.3	67.0
2830	Colorado, Grant and Stanton Counties (M-N)	35.2	2.1	2.2	22.8
	Southern Hamilton and Kearny Counties	5.9			2.3
	Southern Kearny County (Arkansas River valley?)	8.9
	Northern Morton and Stevens Counties	11.2
	sub-totals	61.2			25.1	86.3

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):

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

in which: V_t 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,
A_n 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 + ...
3,240	A0	0
3,230	A1		18.8
3,220	A2		37.7
3,210	A3		57.1
3,200	A4		79.2
3,190	A5		103.5
3,180	A6		127.1
3,170	A7		154.7
3,160	A8		189.8
3,150	A9		229.9
3,140	A10		262.7
3,130	A11		292.8
3,120	A12		321.5
3,110	A13		349.3
3,100	A14		374.8
3,090	A15		405.2
3,080	A16		434.9
3,070	A17		460.9
3,060	A18		486.5
3,050	A19		509.2
3,040	A20		532.3
3,030	A21		554.5
3,020	A22		574.0
3,010	A23		593.5
3,000	A24		612.7
3,090	A25		631.5
3,080	A26		650.3
3,070	A27		670.7
3,060	A28		688.5
3,050	A29		705.9
3,040	A30		727.5
3,030	A31		747.8
3,020	A32		766.1
3,010	A33		786.2
2,900	A34		806.3
2,890	A35		826.5
2,880	A36		844.5
2,870	A37		861.2
2,860	A38		877.5
2,850	A39		891.6
2,840	A40		904.4
2,830	A41		917.0
2,820	A42		928.2
2,810	A43		940.6
2,800	A44		951.9
2,790	A45		970.8
2,780	A46	976.8
Totals		976.8	24,858.0

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	Conversion factor		Anion	Conversion factor
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
27-35-24ac	1	Npl, No	0.3
27-39-13ac	2	Kd, Kc	1.3
28-38- 4cc	3	Npl, No	1.7
29-35-15ab	4	Npl	1.3
29-36-23ddd	5	Npl	3.1
29-36-30bc	6	Npl, No	1.3
29-42-Ildc	7	Kd, Kc, TRd	1.6
30-37-36bc	8	Npl	1.0
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.

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