University of Virginia Library

WATER RESOURCES AND AGRICULTURE

Potable water is a major want in Chaco Canyon today, but was it
always so? In 1877 Jackson camped three days at a muddy pool 250

yards west of Pueblo del Arroyo. Not until the very morning of his
departure did he find the ancient stairway up the cliff back of Pueblo
Bonito and the deep, half-filled water pockets beyond. Richard
Wetherill drew upon these latter, letting a daily ration down over the
cliff by rope and bucket, until a well had been dug in the Chaco wash;
he also built an earth dam to increase the storage capacity of the
pockets and later replaced it with one of concrete (verbal statement
of John Wetherill, 1921). Nine hundred years before, women and
girls from Pueblo Bonito climbed the old stairway to that same source
of cool, clear water and back again, each with an olla balanced upon
her head.

Deep as they are, the water-worn cavities on the cliff overlooking
Pueblo Bonito were reservoirs of limited capacity. They can scarcely
have met the yearlong needs of the village. But, visited upon occasion,
they offered opportunity for feminine gossip and a change from, presumably,
the more frequented waterholes down on the canyon floor.
If we can accept Hosteen Beyal's recollections of 1840 or thereabout,
when the water table was only 2 or 3 feet below the surface and a
succession of shallow, willow-bordered pools marked the middle of
the valley, another such series must have been present when like conditions
prevailed back in the days of Pueblo Bonito. These pools
naturally vanished as floodwaters cut away the intervening sod and
thus initiated an arroyo system. Being shallow-rooted, willows were
doomed to disappear as the water table fell beyond reach of their roots.

According to Jackson, willows and cottonwoods were still fairly
numerous in 1877. Most of them, however, had disappeared before
1920, the year of our reconnaissance. At that time we noted several
cottonwood trees on the south side of the canyon, east of Wejegi, and
others here and there. A lone example was growing near the windmill
in the arroyo west of Una Vida, and two more, similarly situated,
stood a quarter-mile below Pueblo del Arroyo. These latter clearly
had slumped from surface level with caving of the arroyo bank. One
of them, transported a mile farther downstream, still flourished in
1924. Clustered willows sprouted on gully sandbars each spring, but
their numbers decreased from year to year as the channel grew wider
and deeper.

To test the quality of Chaco Canyon water and to measure the
effect of floodwaters upon that quality, we submitted several samples
to the U. S. Department of Agriculture for analysis in 1923 and again
in 1925. I desire at this time to acknowledge our indebtedness to
C. S. Scofield, then senior agriculturist, in charge, Office of Western

Irrigation Agriculture, and to J. F. Breazeale, also of that office,
for the following report:

Quality of water samples from Chaco Canyon, N. Mex., expressed in parts
per million

               

Sample No.	Ca	Mg	HCO3	Cl	SO4	NO3	Total salts
1	30	tr.	240	72	108	tr.	432
2	36	5	264	42	236	tr.	640
3	33	tr.	336	42	169	2	616
4	36	0	312	42	172	2	568
5	30	0	240	tr.	164	2	496
6	138	6	216	0	725	5	1,304
7	105	2	192	0	436	0	848

Description of samples

• No. 1, First floodwaters of 1923, collected July 9.

• No. 2, N.G.S. well, collected July 10, 1923.

• No. 3, N.G.S. well, June 24, 1925, before cleaning.

• No. 4, N.G.S. well, June 26, 1925, after cleaning.

• No. 5, Floodwater, June 24, 1925.

• No. 6, Rafael well, July 16, 1925.

• No. 7, Surface water, Kinbiniyol alluviation plain near Navaho cornfield,
  July 15, 1925.

Character of salts expressed as reacting values or milligram equivalents

               

Sample No.	Ca	Mg	HCO3	Cl	SO4	Total acids	Na[2]
1	1.5	tr.	3.9	2.0	2.2	8.1	82
2	1.8	0.4	4.3	1.2	4.9	10.4	83
3	1.6	0	5.5	1.2	3.5	10.2	84
4	1.8	0	5.1	1.2	3.6	9.9	82
5	1.5	0	4.0	tr.	3.4	7.4	80
6	6.9	0.5	3.5	0	15.1	18.6	60
7	5.2	0.2	3.1	0	9.1	12.2	56

In his letter of August 24, 1925, transmitting the foregoing results,
Mr. Scofield says:

Mr. Scofield adds that there was no appreciable change in the
quality of the water between 1923 and 1925. This was true also, as
one might expect, in samples taken both years from the Expedition
well and from the reconditioned Wetherill well, a hundred yards
downstream.

The last sentence quoted from Mr. Scofield's letter echoes a thought
he had previously expressed, namely, that Chaco Canyon water might
prove unsuitable for irrigation. This possibility prompted an analysis
of soils from fields presumably cultivated by the Bonitians. The results
are reported in our next chapter. It may be noted in passing,
however, that a calcium deficiency and an excess of sodium salts in
the soil samples analyzed have left them impervious to water and
therefore incapable of producing crops. Poor soil thus becomes a
second probable cause for abandonment of Pueblo Bonito. Together,
poor soil and the twelfth-century arroyo would have frustrated every
Bonitian effort toward large-scale agriculture in Chaco Canyon.

There are no springs in the canyon now, but seeps here and there,
chiefly at the heads of rincons, may have been more productive in
times past. Rushes still grow below these seepage zones, but they are
noticeably smaller and less sturdy than those used in ceiling construction
and in floor mats at Pueblo Bonito. This fact suggests a more
generous rainfall when the pueblo was inhabited. On the basis of
our incomplete observations we estimated at 10 inches the current
annual precipitation, but geologists studying the local situation reason
that even one additional inch per year would cause existing seeps to
flow again.

The most active seep seen by members of our party was in a shallow
sandstone cave in upper Rincon del Camino, about a mile and a half
northwest of Pueblo Bonito. It had been developed and carefully
protected for domestic use by Dan Cly, one of our Navaho workmen,
who resided nearby. As is evident from the following analysis, the
water is exceptionally pure:

   

Ca	Mg	HCO3	Cl	SO4	NO3	Total salts
30	0	120	0	48	0	152

Floodwaters following midsummer rains make a noisy approach,
at once fascinating and frightening. Time after time we watched
unbelieving as they methodically undercut the arroyo banks and

carried them away, yard by cubic yard (pl. 4, upper). During our
seven summers in Chaco Canyon, every storm that passed meant an
interruption to our work while we repaired approaches to the road
crossing.

Despite all the destruction they have caused, these recurrent floods
performed one worthy service: they laid bare a partial profile of
Chaco Canyon history. Across from Pueblo del Arroyo a low mound
in midvalley marks a small Pueblo III ruin. One corner had already
been exposed when W. H. Jackson in 1877 observed that the foundations
lay "five or six feet below the general level." The arroyo, then
16 feet deep, was 12 feet deeper in 1920, when, to judge from what
remained, fully half the little ruin had been undermined and washed
away.

Both above and below the surface on which that house was erected,
silt deposited by gently flowing waters formed uniform layers extending
right and left toward the canyon walls (pl. 4, lower). Obviously,
when those silt layers were laid down a lush ground cover was
present to hinder and delay runoff. Our test pits at a number of places
showed like stratification, although nearer the cliff the overburden was
sometimes only 2 feet thick.

The prehistoric arroyo.—Bryan (1925, 1926) described the origin
and development of the present-day arroyo and compared it with one
that existed in Pueblo Bonito times. This latter, which we plotted
for more than a quarter mile, apparently did not exceed 12 or 13 feet
in depth. Nevertheless, it could have brought about what the present
arroyo is even now accomplishing, namely, transformation of Chaco
Canyon from a suitable place of residence into a waste incapable of
supporting more than a few scattered families.

An interval of approximately 800 years separates this modern gully
and its predecessor. After the older one had run its course it was
gradually filled with alluvium and then buried under an additional 5
or 6 feet, as we have seen. Thus the old channel was completely
hidden until exposed by its present-day parallel. What other secrets
lie concealed by those 5 feet of silt is one of the tantalizing mysteries
connected with Pueblo Bonito.

W. H. Jackson first called attention to this buried channel. A cross
section of it near Pueblo del Arroyo showed, 14 feet below the
surface, an irregular stratum of potsherds, flint chips, and bone fragments—household
and workshop waste from the trash piles of Pueblo
Bonito. Here, too, apparently brought in by floodwaters the previous
summer, was a human skull from an unmarked upcanyon grave. A

lesser stratum of sherds on the south bank led up to the small arroyoside
ruin above mentioned (Jackson, 1878, pp. 443-444).

The prehistoric arroyo presumably reached its climax about the
middle of the twelfth century. We draw this inference because Late
Bonitian potsherds were found on the bottom of it and because new
house construction at Pueblo Bonito seems to have come to an end
by that time. Of 52 datable timbers recovered during our excavations
only 4 were felled after A.D. 1100, and the latest of these was cut in
1130 (Douglass, 1935, p. 51). Since the present 30-foot channel
has already been a century in the making, we may, employing the
same time gage, assume its predecessor had a beginning somewhere
around 1075. Bryan (1941, p. 231) dates the period of refill and
alluviation between 1250 and 1400. By 1500 or 1600 ecological equilibrium
had been reestablished and Chaco Canyon was once again a
fit place in which to live.

The Navaho were quick to discover this fact, for the upper Chaco,
with the mesa country northward along the Continental Divide to the
Gobernador, was their tribal birthplace and nursery. It was here
they gathered the numerical strength for recurrent depredations that
all but wiped out the Jemez towns by 1622 (Hodge, in Ayer, 1916,
p. 243). With Navaho acquiescence Pueblo refugees from the aftermath
of their 1680 revolt against Spanish dominance found brief
asylum in this same region (Kidder, 1920).