WATER SUPPLY.
BY G. K. GILBERT.
The following discussion is based upon a special study of the
drainage-basin of Great Salt Lake.
INCREASE OF STREAMS.
The residents of Utah who practice irrigation have observed that many
of the streams have increased in volume since the settlement of the
country. Of the actuality of this increase there can be no question.
A popular impression in regard to the fluctuations of an unmeasured
element of climate may be very erroneous, as, for example, the
impression that the rainfall of the timbered states has been diminished
by the clearing of the land, but in the case of these streams relative
measurements have practically been made. Some of them were so fully
in use twenty years ago that all of their water was diverted from
its channels at the “critical period”, and yet the dependent fields
suffered from drought in the drier years. Afterward, it was found that
in all years there was enough water and to spare, and operations were
extended. Additional canals were dug and new lands were added to the
fields; and this was repeated from time to time, until in many places
the service of a stream was doubled, and in a few it was increased
tenfold, or even fiftyfold. It is a matter of great importance to the
agricultural interests, not only of Utah but of the whole district
dependent on irrigation, that the cause or causes of this change shall
be understood. Until they are known we cannot tell whether the present
gain is an omen of future gain or of future loss, nor whether the
future changes are within or beyond our control. I shall therefore take
the liberty to examine somewhat at length the considerations which are
supposed by myself or others to bear upon the problem.
Fortunately we are not compelled to depend on the incidental
observations of the farming community for the amount of the increase
of the streams, but merely for the fact of their increase. The amount
is recorded in an independent and most thorough manner, by the
accumulation of the water in Great Salt Lake.
RISE OF GREAT SALT LAKE.
A lake with an outlet has its level determined by the height of the
outlet. Great Salt Lake, having no outlet, has its level determined by
the relation of evaporation to inflow. On one hand the drainage of a
great basin pours into it a continuous though variable tribute; on the
other, there is a continuous absorption of its water by the atmosphere
above it. The inflow is greatest in the spring time, while the snows
are melting in the mountains, and least in the autumn after the melting
has ceased, but before the cooling of the air has greatly checked
evaporation on the uplands. The lake evaporation is greatest in summer,
while the air is warm, and least in winter. Through the winter and
spring the inflow exceeds the evaporation, and the lake rises. In the
latter part of the summer and in autumn the loss is greater than the
gain, and the lake falls. The maximum occurs in June or July, and the
minimum probably in November. The difference between the two, or the
height of the annual tide, is about 20 inches.
But it rarely happens that the annual evaporation is precisely equal
to the annual inflow, and each year the lake gains or loses an amount
which depends upon the climate of the year. If the air which crosses
the drainage basin of the lake in any year is unusually moist, there
is a twofold tendency to raise the mean level. On one hand there
is a greater precipitation, whereby the inflow is increased, and
on the other hand there is a less evaporation. So, too, if the air
is unusually dry, the inflow is correspondingly small, the loss by
evaporation is correspondingly great, and the contents of the lake
diminish. This annual gain or loss is an expression, and a very
delicate expression, of the mean annual humidity of a large district of
country, and as such is more trustworthy than any result which might
be derived from local observations with psychrometer and rain gauge.
A succession of relatively dry years causes a progressive fall of the
lake, and a succession of moist years a progressive rise. As the water
falls it retires from its shore, and the slopes being exceedingly
gentle the area of the lake is rapidly contracted. The surface for
evaporation diminishes and its ratio to the inflow becomes less. As the
water rises the surface of the lake rapidly increases, and the ratio of
evaporation to inflow becomes greater. In this way a limit is set to
the oscillation of the lake as dependent on the ordinary fluctuations
of climate, and the cumulation of results is prevented. Whenever the
variation of the water level from its mean position becomes great,
the resistance to its further advance in that direction becomes
proportionally great. For the convenience of a name, I shall speak of
this oscillation of the lake as the _limited oscillation_. It depends
on an oscillation of climate which is universally experienced, but
which has not been found to exhibit either periodicity, or synchrony
over large areas, or other features of regularity.
Beside the annual tide and the limited oscillation, the lake has been
found to exhibit a third change, and this third or _abnormal_ change
seems to be connected with the increase of the tributary streams. In
order to exhibit it, it will be necessary to discuss somewhat fully the
history of the rise and fall of the lake, and I shall take occasion at
the same time to call attention to the preparations that have recently
been made for future observations.
Previous to the year 1875 no definite record was made. In 1874 Prof.
Joseph Henry, secretary of the Smithsonian Institution, began a
correspondence with Dr. John R. Park, of Salt Lake City, in regard to
the fluctuations and other peculiarities of the lake, and as a chief
result a systematic record was begun. With the coöperation of Mr. J.
L. Barfoot and other citizens of Utah, Dr. Park erected a graduated
pillar at Black Rock, a point on the southern shore which was then a
popular summer resort. It consisted of a granite block cut in the form
of an obelisk and engraved on one side with a scale of feet and inches.
It was set in gravel beneath shallow water, with the zero of its scale
near the surface. The water level was read on the pillar by Mr. John
T. Mitchell at frequent intervals from September 14, 1875, to October
9, 1876, when the locality ceased to be used as a watering place, and
the systematic record was discontinued. Two observations were made by
the writer in 1877, and it was found in making the second that the
shifting gravel of the beach had buried the column so deeply as to
conceal half the graduation.
Dr. Park has kindly furnished me a copy of Mr. Mitchell’s record.
The observer was instructed to choose such times of observation that
the influence of wind storms upon the level of the lake would be
eliminated, and the work appears to have been faithfully performed.
_Record of the height of Great Salt Lake above the zero of the granite
pillar at Black Rock._
+----------------------+-------------+-------------------+
| Date. | Reading. | Wind. |
+------+----------+----+-----+-------+----------+--------+
| | | | | | | |
| Year.| Month. |Day.|Feet.|Inches.|Direction.| Force. |
+------+----------+----+-----+-------+----------+--------+
|1875 |September | 14 | 0 | 6 | N. |Gentle. |
| | | 22 | 0 | 5¹⁄₂ | N. E. |Quiet. |
| | | 25 | 0 | 5 | N. E. |Quiet. |
| |October | 6 | 0 | 4¹⁄₂ | N. |Quiet. |
| | | 12 | 0 | 4 | N. E. |Quiet. |
| | | 18 | 0 | 3¹⁄₂ | N. E. |Quiet. |
| | | 26 | 0 | 3 | N. E. |Quiet. |
| |November | 9 | 0 | 2 | W. |Quiet. |
| | | 16 | 0 | 1¹⁄₂ | N. |Quiet. |
| | | 23 | 0 | 4 | N. E. |Quiet. |
| | | 29 | 0 | 5¹⁄₂ | E. |Quiet. |
| |December | 7 | 0 | 5 | E. |Quiet. |
| | | 14 | 0 | 5¹⁄₂ | E. |Quiet. |
| | | 21 | 0 | 6 | N. E. |Quiet. |
|1876 |January | 5 | 0 | 8 | N. E. |Quiet. |
| | | 11 | 0 | 8¹⁄₂ | N. E. |Quiet. |
| | | 29 | 0 | 9 | E. |Quiet. |
| |February | 1 | 0 | 9 | S. E. |Quiet. |
| | | 15 | 0 | 9¹⁄₂ | -- |Calm. |
| | | 22 | 0 | 9¹⁄₂ | N. E. |Quiet. |
| |March | 15 | 0 | 11 | N. E. |Quiet. |
| | | 22 | 1 | 0 | N. E. |Quiet. |
| | | 28 | 1 | ¹⁄₂ | N. E. |Quiet. |
| |April | 17 | 1 | 2 | -- |Calm. |
| | | 25 | 1 | 3 | N. E. |Quiet. |
| |May | 2 | 1 | 4 | N. E. |Quiet. |
| | | 22 | 1 | 9 | N. |Quiet. |
| |June | 2 | 1 | 11 | W. |Quiet. |
| | | 8 | 2 | 0 | -- |Calm. |
| | | 13 | 2 | 2 | N. E. |Quiet. |
| | | 23 | 2 | 4 | N. E. |Quiet. |
| | | 30 | 2 | 6 | S. |Quiet. |
| |July | 18 | 2 | 3 | N. E. |Quiet. |
| | | 25 | 2 | 4 | N. E. |Quiet. |
| |August | 1 | 2 | 3 | N. E. |Quiet. |
| | | 10 | 2 | 2 | N. E. |Quiet. |
| | | 22 | 1 | 9 | N. E. |Quiet. |
| | | 29 | 1 | 8 | S. E. |Strong. |
| | | 30 | 1 | 8 | N. |Quiet. |
| |September | 14 | 1 | 7 | -- |Calm. |
| | | 19 | 1 | 6¹⁄₂ | N. |Quiet. |
| | | 26 | 1 | 6 | -- |Calm. |
| |October | 9 | 1 | 5¹⁄₂ | N. E. |Quiet. |
|1877 |July | 12 | 2 | 0 | -- |Calm. |
| |October | 19 | 0 | 10 | -- |Calm. |
+------+----------+----+-----+-------+----------+--------+
Comparing the October observations for three years, it appears that the
lake rose 13 inches from 1875 to 1876, and fell in the next year 6¹⁄₂
inches.
[Illustration: SKETCH OF BLACK ROCK AND VICINITY, UTAH TERRITORY.
_Prepared to show the position of the graduated pillar erected by Dr.
John Park for observations on the water-level of Great Salt Lake, and
the position of the granite bench-mark._]
The Black Rock pillar has not the permanence that is desirable.
Although it has thus far been only the more firmly established by the
action of the waves, it is still true that the lake is encroaching
on the land in this part of the coast, and a storm may at any time
undermine and overthrow the pillar. To provide for such a contingency
it was determined to establish a bench mark out of reach of the waves,
and connect it with the pillar by leveling, so that if the existing
standard should be destroyed its record would still have a definite
meaning, and the relative height of a new standard could be ascertained
with precision. In this undertaking I was joined by Mr. Jesse W. Fox,
a gentleman who has long held the office of territorial surveyor of
Utah. A suitable stone was furnished by the Hon. Brigham Young, and was
carried to Black Rock without charge through the courtesy of Mr. Heber
P. Kimball, superintendent of the Utah Western Railroad. The block is
of granite, and is three feet in length. It was sunk in the earth, all
but a few inches, on the northern slope of a small limestone knoll just
south of the railroad track at Black Rock. Its top is dressed square,
about 10 × 10 inches, and is marked with a +. It will be convenient to
speak of the top of this monument as the _Black Rock bench_. On the
11th of July, 1877, the surface of the lake was 34.5 feet below the
bench, and it then marked 2.0 feet on the pillar erected by Dr. Park.
The zero of the observation pillar is therefore 36.5 feet below the
bench.
The accompanying topographic sketch will serve at any time to identify
the position of the bench.
After consultation with Dr. Park, I concluded that it would be
better not to depend on the Black Rock station for observations in
the future--at least in the immediate future--and other points were
discussed. Eventually it was determined to establish a new station near
Farmington, on the eastern shore of the lake. The point selected is in
an inlet so sheltered that a heavy swell in the lake will not interfere
with accurate observation. At the present stage of water the spot is
well adapted to the purpose, and it can be used with the water 2 feet
lower or 5 feet higher. I was not able to attend personally to the
erection of the pillar, but left the matter in the hands of Mr. Jacob
Miller, of Farmington, who writes me that it was placed in position and
the record begun on the 24th of November, 1877. The pillar is of wood,
and is graduated to inches for 9 feet of its length.
On the day of its establishment the reading of the water surface was 2
feet 1 inch. On the 21st of January, 1878, the reading was 2 feet 1¹⁄₂
inches.
The Farmington and Black Rock pillars are 23 miles apart. The relative
height of their zeros will be ascertained as soon as practicable by
making coincident readings, during still weather, of the water surface
at the two stations. It is already known that the Farmington zero is
_approximately_ 16 inches lower than the Black Rock.
A stone “bench” or monument for permanent reference has also been
placed on rising ground near the observation pillar, and the two will
be connected by spirit level. The Farmington bench is of gneiss, and
is marked with a + in the same manner as the Black Rock. The stone was
contributed by Mr. Abbott, of Farmington, and was gratuitously shaped
and placed by Mr. Miller.
Mr. Miller has also voluntarily assumed charge of the record, and will
make or superintend the observations. It will not be practicable to
visit the pillar daily, nor even at _regular_ intervals, but it is
expected that the record will be as full as the one tabulated above.
The following items are to be noted:
1. Time of observation, including year, month, day, and hour.
2. Reading of water surface in feet and inches.
3. Direction and force of wind.
4. Account of wind for the preceding 24 hours.
5. Name of observer.
These observations will not only determine the annual gain or loss of
the lake, but will in a few years give data to construct the curve of
the annual tide.
The history of past changes not having been the subject of record,
it became necessary to compile it from such collateral data as were
attainable. The enquiries inaugurated by Professor Henry have been
prosecuted, and have resulted in a tolerably definite determination of
the principal changes since 1847, together with the indication of a
superior limit to earlier oscillations.
Ever since the settlement of Salt Lake City, in 1847, the islands of
the lake have been used as herd grounds. Fremont and Carrington islands
have been reached by boat, and Antelope and Stansbury islands partly
by boat, partly by fording, and partly by land communication. A large
share of the navigation has been performed by citizens of Farmington,
and the shore is in that neighborhood so flat that the changes of
water level have necessitated frequent changes of landing place. The
pursuits of the boatmen have been so greatly affected that all of the
more important fluctuations were impressed upon their memories, and
most of the changes were so associated with features of the topography
that some estimate of their quantitative values could be made. The
data which became thus available were collated for Professor Henry by
Mr. Miller, a gentleman who himself took part in the navigation, and
of whom I have already had occasion to speak. His results agree very
closely with those derived from an independent investigation of my own,
to which I will now proceed.
Antelope Island is connected with the delta of the Jordan River by a
broad, flat sand bar that has been usually submerged but occasionally
exposed. It slopes very gently toward the island, and just where it
joins it is interrupted by a narrow channel a few inches in depth.
For a number of years this bar afforded the means of access to the
island, and many persons traversed it. By combining the evidence of
such persons it has been practicable to learn the condition of the ford
up to the time of its final abandonment. From 1847 to 1850 the bar was
dry during the low stage of each winter, and in summer covered by not
more than 20 inches of water. Then began a rise which continued until
1855 or 1856. At that time a horseman could with difficulty ford in the
winter, but all communication was by boat in summer. Then the water
fell for a series of years until in 1860 and 1861 the bar was again dry
in winter. The spring of 1862 was marked by an unusual fall of rain and
snow, whereby the streams were greatly flooded and the lake surface was
raised several feet. In subsequent years the rise continued, until in
1865 the ford became impassable. According to Mr. Miller the present
height was attained in about 1868, and there have since occurred only
minor fluctuations.
For the purpose of connecting the traditional history as derived from
the ford with the systematic record that has now been inaugurated, I
visited the bar in company with Mr. Miller on the 19th of October,
1877, and made careful soundings. The features of the ford had
been minutely described, and there was no uncertainty as to the
identification of the locality. We found 9 feet of water on the sand
flat, and 9 feet 6 inches in the little channel at its edge. The
examination was completed at 11 a. m.; at 5 p. m. the water stood at 0
feet 10 inches on the Black Rock pillar; and on the following day at 8
a. m. we marked its level at the place where the Farmington pillar now
stands, our mark being 2 feet 2 inches above the zero of the pillar.
The Antelope Island bar thus affords a tolerably complete record from
1847 to 1865, but fails to give any later details. It happens, however,
that the hiatus is filled at another locality. Stansbury Island is
joined to the mainland by a similar bar, which was entirely above
water at the time of Captain Stansbury’s survey, and so continued for
many years. In 1866, the year following that in which the Antelope bar
became unfordable, the water for the first time covered the Stansbury
bar, and its subsequent advance and recession have so affected the
pursuits of the citizens of Grantsville, who used the island for a
winter herd ground, that it will not be difficult to obtain a full
record by compiling their forced observations. Since undertaking the
inquiry I have had no opportunity to visit that town, but the following
facts have been elicited by correspondence. Since the first flooding of
the bar the depth of water has never been less than 1 foot, and it has
never been so great as to prevent fording in winter. But in the summers
of 1872, 1873, and 1874, during the flood stage of the annual tide,
there was no access except by boat, and in those years the lake level
attained its greatest height. In the spring of 1869 the depth was 4¹⁄₂
feet, and in the autumn of 1877, 2¹⁄₂ feet.
The last item shows that the Stansbury bar is 7 feet higher than the
Antelope, and serves to connect the two series of observations.
[Illustration: _Diagram showing the rise and fall of Great Salt Lake
from 1847 to 1877._
N. S. = Level of new storm line.
O. S. = Level of old storm line.
S. B. = Level of Stansbury Island bar.
A. B. = Level of Antelope Island bar.]
Further inquiries will probably render the record more complete
and exact, but, as it now stands, all the general features of the
fluctuations are clearly indicated. In the accompanying diagram
the horizontal spaces represent years, and the vertical, feet. The
irregular curve shows the height of the lake in different years. Where
it is drawn as a full line the data are definite; the dotted portions
are interpolated.
Upon the same diagram are indicated the levels of two storm lines. The
upper is the limit of wave action at the present time, and is 3 feet
above the winter stage (October, 1877). It is everywhere marked by
drift wood, and in many places by a ridge of sand. Above it there is
a growth, on all steep shores, of sage and other bushes, but those in
immediate proximity are dead, having evidently been killed by the salt
spray. Below the line are still standing the stumps of similar bushes,
and the same can be found 2 or 3 feet below the surface of the water.
The lower storm line was observed by Captain Stansbury in 1850, and
has been described to me by a number of citizens of Utah to whom it
was familiar at that time and subsequently. Like the line now visible,
it was marked by drift wood, and a growth of bushes, including the
sage, extended down to it; but below it there were seen no stumps. Its
position is now several feet under water, and it is probable that the
advancing waves destroyed most of its features, but the vestiges of the
bushy growth above it remain.
The peculiarities of the two storm lines have an important bearing on
the history of the lake. The fact that the belt of land between them
supported sage bushes shows that previous to its present submergence
the lake had not covered it for many years. Lands washed by the brine
of the lake become saturated with salt to such extent that even
salt-loving plants cannot live upon them, and it is a familiar fact
that the sage (_Artemisia sempervirens_) never grows in Utah upon soil
so saline as to be unfavorable for grain. The rains of many years, and
perhaps even of centuries, would be needed to cleanse land abandoned by
the lake so that it could sustain the salt-hating bushes, and we cannot
avoid the conclusion that the ancient storm line had been for a long
period the superior limit of the fluctuations of the lake surface.
To avoid misapprehension, it should be stated that the storm lines
have been described as they appear on the eastern shore of Antelope
Island, a locality where the slope of the ground amounts to three or
four degrees. The circumstances are different at the margin of the
mainland, and especially where the slopes are very gentle. The lake is
so shallow that its equilibrium is greatly disturbed by strong winds.
Its waves are small, but in storms the water is pushed high up on the
land toward which the wind blows, the extreme effects being produced
where the inclination is most gentle. The islands, however, are little
flooded; the water does not accumulate against them, but is driven
past; and the easterly gales that produced the present storm line on
the east shore of Antelope Island may have driven so much water to
the westward as even to have depressed the level in that locality.
Moreover, where the land surface is nearly level, the cleansing by rain
of portions once submerged is indefinitely retarded. On all the flatter
shores the lake is bordered by tracts too saline for reclamation by
the farmer, and either bare of vegetation or scantily covered by
salt-loving shrubs. These tracts are above the modern storm line, and
they acquired their salt during some flood too remote to be considered
in this connection. The largest of them is called the Great Salt Lake
Desert, and has a greater area than the lake itself.
Thus it appears that in recent times the lake has overstepped a bound
to which it had long been subject. Previous to the year 1865, and for
a period of indefinite duration, it rose and fell with the limited
oscillation and with the annual tide, but was never carried above a
certain limiting line. In that year, or the one following, it passed
the line, and it has not yet returned. The annual tide and the limited
oscillation are continued as before, but the lowest stage of the new
regime is higher than the highest stage of the old. The mean stage of
the new regime is 7 or 8 feet higher than the mean stage of the old.
The mean area of the water surface is a sixth part greater under the
new regime than under the old.
The last statement is based on the United States surveys of Captain
Stansbury and Mr. King. The former gathered the material for his map
in 1850, when the water was at its lowest stage, and the latter in the
spring of 1869, when the water was near its highest stage. The one map
shows an area of 1,750 and the other of 2,166 square miles. From these
I estimate the old mean area at 1,820 miles, the new at 2,125 miles,
and the increase at 305 miles, or 17 per cent.
[Illustration: COMPARATIVE MAP
OF
GREAT SALT LAKE, UTAH
COMPILED TO SHOW ITS INCREASE OF AREA
_The topography and later shore-line are taken from the Survey of Mr.
Clarence King, U.S. Geologist; the earlier shore-line from the Survey
of Capt. Howard Stansbury, U.S.A._]
The “abnormal change” of the lake may then be described as an infilling
or rise of the water whereby its ordinary level has been raised 7 or 8
feet and its ordinary area has been increased a sixth part; and this
appears to be distinct from the limited oscillation and annual tide,
which may be regarded as comparatively normal. To account for it a
number of theories have been proposed, and three of them seem worthy
of consideration. They appeal respectively to volcanic, climatic, and
human agencies.
VOLCANIC THEORY.
It has been surmised that upheavals of the land, such as sometimes
accompany earthquakes, might have changed the form of the lake bed
and displaced from some region the water that has overflowed others.
This hypothesis acquires a certain plausibility from the fact that
the series of uplifts and downthrows by which the mountains of the
region were formed have been traced down to a very recent date, but
it is negatived by such an array of facts that it cannot be regarded
as tenable. In the first place, the water has risen against _all_ the
shores and about every island of which we have account. The farmers
of the eastern and southern margins have lost pastures and meadows by
submergence. At the north, Bear River Bay has advanced several miles
upon the land. At the west, a boat has recently sailed a number of
miles across tracts that were traversed by Captain Stansbury’s land
parties. That officer has described and mapped Strong’s Knob and
Stansbury Island as peninsulas, but they have since become islands.
Antelope Island is no longer accessible by ford, and Egg Island, the
nesting ground of the gulls and pelicans, has become a reef. Springs
that supplied Captain Stansbury with fresh water near Promontory Point
are now submerged and inaccessible; and other springs have been covered
on the shores of Antelope, Stansbury, and Fremont islands.
In the second place, the rise of the lake is correlated in time with
the increase of the inflowing streams, which has been everywhere
observed by irrigators, and it is logical to refer the two phenomena to
the same cause.
And, finally, if upheaval could account for the enlargement of the
lake, it would still be inadequate to account for the maintenance
of its increased size, in the face of an evaporation that yearly
removes a layer several feet in depth. The same compensatory principle
that restricts the “limited oscillation” would quickly restore the
equilibrium between inflow and evaporation, in whatever manner it was
disturbed.
CLIMATIC THEORY.
It is generally supposed that the change is a phenomenon of climate,
and this hypothesis includes harmoniously the increase of streams with
the increase of lake surface. By some it is thought that the climate of
the district is undergoing, or has undergone, a permanent change; and
by others that the series of oscillations about a mean condition which
characterizes every climate has in this case developed a moist phase
of exceptional degree and duration. The latter view was my own before
I became aware of the features of the ancient storm line, but it now
appears to me untenable. That a variable surface of evaporation, which
had for a long period recognized a limit to its expansion, should not
merely exceed that limit, but should maintain an abnormal extent for
more than a decade, is in a high degree improbable.
It is far more probable that one of those gradual climatic changes, of
which geology has shown the magnitude and meteorology has illustrated
the slowness, here finds a manifestation. The observed change is
apparently abrupt, and even saltatory; but of this we cannot be
certain, since it is impossible from a record of only thirty years
to eliminate the limited oscillation. It is quite conceivable that
were such elimination effected, the residual change would appear as a
continuous and equable increase of the lake. However that may be, a
certain degree of rapidity of change is necessarily involved, for the
climatic change which is able in a decade to augment by a sixth part
the mean area of evaporation cannot be of exceeding slowness. If we
can ascertain how great a change would be demanded, it will be well to
compare it with such changes as have been observed in other parts of
the country, and see whether its magnitude is such as to interfere with
its assumption.
The prevailing winds of Utah are westerly, and it may be said in a
general way that the atmosphere of the drainage basin of Great Salt
Lake is part of an air current moving from west to east. The basin
having no outlet, the precipitation of rain and snow within its limits
must be counter-balanced by the evaporation. The air current must on
the average absorb the same quantity of moisture that it discharges.
Part of the absorption is from land surfaces and part from water, the
latter being the more rapid.
If, now, the equilibrium be disturbed by an augmented humidity of the
inflowing air, two results ensue. On the one hand the precipitation
is increased, and on the other, the absorbent power of the air being
less, the rate of evaporation is diminished. In so dry a climate the
precipitation is increased in greater ratio than the humidity, and the
rate of evaporation is diminished in less ratio; while of the increased
precipitation an increased percentage gathers in streams and finds its
way to the lake. That reservoir, having its inflow augmented and its
rate of evaporation decreased, gains in volume and grows in breadth
until the evaporation from the added expanse is sufficient to restore
the equilibrium. Giving attention to the fact that the lake receives
a greater percentage of the total downfall than before, and to the
fact that its rate of evaporation is at the same time diminished it is
evident that the resultant augmentation of the lake surface is more
than proportional to the augmentation of the precipitation.
We are therefore warranted in assuming that an increase of humidity
sufficient to account for the observed increase of 17 per cent. in the
size of the lake would modify the rainfall by less than 17 per cent.
The actual change of rainfall cannot be estimated with any degree of
precision, but from a review of such data as are at my command I am led
to the opinion that an allowance of 10 per cent. would be as likely to
exceed as to fall short, while an allowance of 7 per cent. would be at
the verge of possibility.
The rainfall of some other portions of the continent has been recorded
with such a degree of thoroughness and for such a period that a term
of comparison is afforded. In his discussion of the precipitation of
the United States, Mr. Schott has grouped the stations by climatic
districts, and deduced the annual means for the several districts.
Making use of his table on page 154 (Smithsonian Contributions, No.
222), and restricting my attention to the results derived from five
or more stations, I select the following extreme cases of variation
between the mean annual rainfalls of consecutive decades. District I
comprises the sea coast from Maine to Virginia, and the record includes
five or more stations from 1827 to 1867. From the decade 1831-’40 to
the decade 1841-’50 the rainfall increased 6 per cent. District II
comprises the state of New York and adjacent regions, and includes
five or more stations from 1830 to 1866. From the decade 1847-’56 to
the decade 1857-’66 the rainfall increased 9 per cent. District IV
comprises the Ohio Valley and adjacent regions, and includes five
or more stations from 1837 to 1866. From decade 1841-’50 to decade
1851-’60 the rainfall diminished 8 per cent.
The case, then, stands that the best comparable districts and epochs
exhibit extreme fluctuations from decade to decade of from 6 to 9 per
cent, while the rise of Great Salt Lake implies a fluctuation of about
10 per cent. But before deciding that the hypothetical fluctuation
in Utah is extraordinary, consideration should be given to the fact
that in the dry climate of that region a given change in humidity will
produce a relatively great change in rainfall, while an identical
change of rainfall, measured in inches, acquires an exaggerated
importance when expressed as the percentage of a small total rainfall.
Giving due weight to these considerations, I am led to conclude
that the assumed increase of rainfall in Utah is not of incredible
magnitude, and consequently that the hypothesis which ascribes the rise
of the lake to a change of climate should be regarded as tenable. It
by no means follows that it is proven, and so long as it depends on an
assumption the truth of which is merely possible, but not established,
it can claim no more than a provisional acceptance.
It is proper to add that, so far as I entertain the idea of a change of
climate, I do so without referring the change to any local cause. It is
frequently asserted that the cultivated lands of Utah “draw the rain”;
or that the prayers of the religious community inhabiting the territory
have brought water to their growing crops; or that the telegraph
wires and iron rails which gird the country have in some way caused
electricity to induce precipitation; but none of these agencies seem to
be competent. The weather of the globe is a complex whole, each part of
which reacts on every other, and each part of which depends on every
other. The weather of Utah is an interdependent part of the whole, and
cannot be referred to its causes until the entire subject is mastered.
The simpler and more immediate meteoric reactions have been so far
analyzed that their results are daily predicted; but the remote sources
of our daily changes, as well as the causes of the greater cycles of
change, are still beyond our reach. Although withdrawn from the domain
of the unknowable, they remain within that of the unknown.
THEORY OF HUMAN AGENCIES.
The only remaining theory of value is the one advocated by Professor
Powell: that the phenomena are to be ascribed to the modification of
the surface of the earth by the agency of man. The rise of the lake
and the increase of streams have been observed since the settlement of
the country by the white man, and the sage brush on the old storm line
shows that they had not been carried to the same extent at any previous
period in the century. They have coincided in time with the extension
of the operations of civilization; and the settlers attach this idea to
the facts in detail as well as in general. They have frequently told me
that wherever and whenever a settlement was established, there followed
in a few years an increase of the water supply, and these statements
have been supported by such enumerations of details that they seem
worthy of consideration. If they are well founded, the secret of the
change will surely be found among the modifications incident to the
operations of the settler.
Similar testimony was gathered by Prof. Cyrus Thomas in 1869 in regard
to the increase of water supply at the western edge of the plains, and
the following conclusion appears in his report to Dr. Hayden (page 237
of the reprint of Dr. Hayden’s reports for 1867, 1868, and 1869):
All this, it seems to me, must lead to the conclusion that since the
territory [Colorado] has begun to be settled, towns and cities built
up, farms cultivated, mines opened, and roads made and travelled,
there has been a gradual increase of moisture. Be the cause what it
may, unless it is assumed that there is a cycle of years through which
there is an increase, and that there will be a corresponding decrease,
the fact must be admitted upon this accumulated testimony. I therefore
give it as my firm conviction that this increase is of a permanent
nature, and not periodical, and that it has commenced within eight
years past, and that it is in some way connected with the settlement
of the country, and that as the population increases the moisture will
increase.
Notwithstanding the confidence of Professor Thomas’s conclusions, he
appears to have reached them by a leap, for he makes no attempt to
analyze the influence of civilized man on nature to which he appeals.
Before we accept his results, it will be necessary to inquire in what
way the white man has modified the conditions by which the water supply
is controlled.
To facilitate this inquiry, an attempt will be made to give a new and
more convenient form to our expression of the amount of change for
which it is necessary to account in the basin of Great Salt Lake.
The inflow of the lake is derived chiefly from three rivers, and is
susceptible of very exact determination. Thorough measurement has not
yet been made, but there has been a single determination of each river
and minor stream, and a rough estimate can be based on them. The Bear
and the Weber were measured in October, 1877, and I am led by the
analogy of other streams and by the characters of the river channels
to judge that the mean volume of the Bear for the year was twice its
volume at the date of measurement, and that of the Weber four times.
The mean flow of the Jordan can be estimated with more confidence, for
reasons which will appear in a following chapter. The “supply from
other sources” mentioned in the table includes all the creeks that flow
from the Wasatch Mountains, between Draper and Hampden, together with
the Malade River, Blue Creek, the creeks of Skull and Tooele Valleys,
and the line of springs that encircles the lake.
+---------------------------------------------+----------+-----------+
| | Measured | Estimated |
| |volume in |mean volume|
| Rivers, etc. | feet per | in feet |
| | second. |per second.|
+---------------------------------------------+----------+-----------+
|Bear River, measured October 4, 1877, | | |
| at Hampden Bridge | 2,600 | 5,200 |
|Weber River, measured October 11, near Ogden | 500 | 2,000 |
|Jordan River, measured July 8, near Draper | 1,275 | 1,000 |
|Supply from other sources | -- | 1,800 |
| +----------+-----------+
| Total | -- | 10,000 |
|Deduct the water used in irrigation | -- | 600 |
| +----------+-----------+
| Remainder | -- | 9,400 |
+---------------------------------------------+----------+-----------+
The result expresses the mean inflow to the lake in 1877, and is
probably not more than 25 per cent. in error. The total inflow for the
year would suffice to cover the lake to a depth of 60 inches. In the
same year (or from October, 1876, to October, 1877) the lake fell 6¹⁄₂
inches, showing that the loss by evaporation was by so much greater
than the gain by inflow. The total annual evaporation of inflowing
water may therefore be placed provisionally at 66¹⁄₂ inches. If we add
to this the rain and snow which fall on the lake, we deduce a total
annual evaporation of about 80 inches of water; but for the present
purpose it will be more convenient to consider the former figure.
The extent of the Salt Lake basin is about 28,500 square miles. The
western portion, amounting to 12,500 miles, sends no water to the
lake, yielding all its rainfall to evaporation within its own limits.
The remaining 16,000 miles includes both plains and mountains, and
its tribute is unequal. To supply 66¹⁄₂ inches annually to the whole
area of the lake, 2,125 miles, it must yield a sheet of water with an
average thickness of 8.83 inches. In former times, when the lake had an
area of only 1,820 miles, the yield of the same area was 7.43 inches.
The advance from 7.43 to 8.83, or the addition of 1 inch and 4 tenths
to the mean outflow of the district, is the phenomenon to be accounted
for.
All the water that is precipitated within the district as rain or snow
returns eventually to the air, but different portions are returned
in different ways. Of the snow, a portion is melted and a portion is
evaporated without melting. Of the melted snow and the rain, a part is
absorbed by vegetation and soil, and is afterward reabsorbed by the
air; another part runs from the surface in rills, and a third part
sinks into the underlying formations and afterward emerges in springs.
The streams which arise from springs and rills are again divided. Part
of the water is evaporated from the surfaces of the streams and of
fresh water lakes interrupting their courses. Another part enters the
adjacent porous soils, and either meets in them the air by which it is
slowly absorbed, or else so saturates them as to produce marshes from
which evaporation progresses rapidly at the surface. The remainder
flows to Great Salt Lake, and is in time evaporated from its surface.
The lesser portion of the precipitation enters the lake; the greater
is intercepted on the way and turned back to the air. Whatever man
has done to clear the way for the flowing water has diminished local
evaporation and helped to fill the lake. Whatever he has done to
increase local evaporation has tended to empty the lake.
The white man has modified the conditions of drainage, first, by the
cultivation of the soil; second, by the raising of herds; and, third,
by the cutting of trees.
1. By plowing the earth the farmer has rendered it more porous and
absorbent, so that a smaller percentage of the passing shower runs off.
He has destroyed the native vegetation, and replaced it by another
that may or may not increase the local evaporation; but this is of
little moment, because his operations have been conducted on gentle
slopes which in their natural condition contributed very little to the
streams. It is of greater import that he has diverted water already
accumulated in streams, and for the purposes of irrigation has spread
it broadly upon the land, whence it is absorbed by the air. In this way
he has diminished the inflow of the lake.
Incidental to the work of irrigation has been what is known as the
“opening out” of springs. Small springs are apt to produce bogs from
which much water is evaporated, and it has been found that by running
ditches through them the water can be gathered into streams instead.
The streams of water thus rescued from local dissipation are consumed
in irrigation during a few months of the year, but for the remainder
go to swell the rivers, and the general tendency of the work is to
increase the inflow of the lake. A similar and probably greater result
has been achieved by the cutting of beaver dams. In its natural
condition every stream not subject to violent floods was ponded from
end to end by the beaver. Its water surface was greatly expanded,
and its flood plains were converted into marshes. The irrigator has
destroyed the dams and drained the marshes.
There are a few localities where drainage has been resorted to for the
reclamation of wet hay lands, and that work has the same influence on
the discharge to the lake.
2. The area affected by grazing is far greater than that affected by
farming. Cattle, horses, and sheep have ranged through all the valleys
and upon all the mountains. Over large areas they have destroyed the
native grasses, and they have everywhere reduced them. Where once the
water from rain was entangled in a mesh of vegetation and restrained
from gathering into rills, there is now only an open growth of bushes
that offer no obstruction. Where once the snows of autumn were spread
on a non-conducting mat of hay, and wasted by evaporation until the
sunshine came to melt them, they now fall upon naked earth and are
melted at once by its warmth.
The treading of many feet at the boggy springs compacts the spongy mold
and renders it impervious. The water is no longer able to percolate,
and runs away in streams. The porous beds of brooklets are in the same
way tramped and puddled by the feet of cattle, and much water that
formerly sank by the way is now carried forward.
In all these ways the herds tend to increase the inflow of the lake,
and there is perhaps no way in which they have lessened it.
3. The cutting of trees for lumber and fence material and fuel has
further increased the streams. By the removal of foliage, that share
of the rain and snow which was formerly caught by it and thence
evaporated, is now permitted to reach the ground, and some part of it
is contributed to the streams. Snow beds that were once shaded are
now exposed to the sun, and their melting is so accelerated that a
comparatively small proportion of their contents is wasted by the wind.
Moreover, that which is melted is melted more rapidly, and a larger
share of it is formed into rills.
On the whole, it appears that the white man causes a greater percentage
of the precipitation in snow to be melted and a less percentage to be
evaporated directly. This follows from the destruction of trees and of
grass. By reducing the amount of vegetation he gives a freer flow to
the water from rain and melting snow and carries a greater percentage
of it to streams, while a smaller percentage reaches the air by
evaporation from the soil. By the treading of his cattle he diminishes
the leakage of the smaller water channels, and conserves the streams
gathered there. By the same means and by the digging of drains he
dries the marshes and thereby enlarges the streams. In all these ways
he increases the outflow of the land and the inflow of the lake. He
diminishes the inflow in a notable degree only by irrigation.
The direct influence of irrigation upon the inflow is susceptible of
quantitative statement. Four hundred square miles of land in Utah and
Idaho are fertilized by water that would otherwise flow to the lake,
and they dissipate annually a layer of about 20 inches. To supply these
20 inches the drainage district of 16,000 miles yields an average layer
of 0.5 inch, and this yield is in addition to the 1.4 inches required
to maintain the increase of lake surface. The total augmentation of the
annual water supply is therefore represented by a sheet 1.9 inches in
depth covering the entire district.
The indirect influence of irrigation, and the influences exerted by the
grazier and the woodman, cannot be estimated from any existing data,
but of their tendencies there can be no question. To some extent they
diminish local evaporation, and induce a larger share of the rainfall
to gather in the streams; and to one who has contrasted the district in
question with similar districts in their virgin condition, there seems
no extravagance in ascribing to them the whole of the observed change.
In the valley of the Mississippi and on the Atlantic coast, it has been
observed that the floods of rivers are higher than formerly, and that
the low stages are lower, and the change has been ascribed by Ellet
and others to the destruction of the native vegetation. The removal
of forests and of prairie grasses is believed to facilitate the rapid
discharge from the land of the water from rain and melted snow, and to
diminish the amount stored in the soil to maintain springs. In an arid
country like Utah, where the thirst of the air is not satisfied by the
entire rainfall, any influence that will increase the rapidity of the
discharge must also increase the amount of the discharge. The moisture
that lingers on the surface is lost.
On the whole, it may be most wise to hold the question an open one
whether the water supply of the lake has been increased by a climatic
change or by human agency. So far as we now know, neither theory is
inconsistent with the facts, and it is possible that the truth includes
both. The former appeals to a cause that may perhaps be adequate, but
is not independently known to exist. The latter appeals to causes known
to exist but quantitatively undetermined.
It is gratifying to turn to the economic bearings of the question, for
the theories best sustained by facts are those most flattering to the
agricultural future of the Arid Region. If the filling of the streams
and the rise of the lake were due to a transient extreme of climate,
that extreme would be followed by a return to a mean condition, or
perhaps by an oscillation in the opposite direction, and a large share
of the fields now productive would be stricken by drought and returned
to the desert.
If the increase of water supply is due to a progressive change of
climate forming part of a long cycle, it is practically permanent, and
future changes are more likely to be in the same advantageous direction
than in the opposite. The lands now reclaimed are assured for years to
come, and there is every encouragement for the work of utilizing the
existing streams to the utmost.
And finally, if the increase of water supply is due to the changes
wrought by the industries of the white man, the prospect is even
better. Not only is every gain of the present assured for the future,
but future gain may be predicted. Not alone are the agricultural
facilities of this district improving, but the facilities in the whole
Rocky Mountain Region are improving and will improve. Not only does the
settler incidentally and unconsciously enhance his natural privilege,
but it is possible, by the aid of a careful study of the subject, to
devise such systematic methods as shall render his work still more
effectual.
FARMING WITHOUT IRRIGATION.
The general rule that agriculture in Utah is dependent on artificial
irrigation finds exception in two ways. First, there are some
localities naturally irrigated; and, second, there is at least one
locality of which the local climate permits dry farming.
Along the low banks of many streams there are fertile strips of
land. The soil is in every such case of a porous nature, and water
from the stream percolates laterally and rises to the roots of the
plants. Nearly all such lands are flooded in spring time, and they
are usually devoted to hay as an exclusive crop; but some of them are
above ordinary floods and are suited for other uses. It rarely happens,
however, that they are farmed without some irrigation, for the reason
that the use of the convenient water render the harvest more secure and
abundant.
The same fertility is sometimes induced by subterranean waters which
have no connection with surface streams. In such cases there is
usually, and perhaps always, an impervious subsoil which retains
percolating water near the surface. A remarkable instance of this sort
is known at the western base of the Wasatch Mountains. A strip of land
from 20 to 40 rods broad, and marking the junction of the mountain
slope with the plain, has been found productive from Hampton’s Bridge
to Brigham City, a distance of 18 miles. In some parts it has been
irrigated, with the result of doubling or trebling the yield, but where
water has not been obtained, the farmer has nevertheless succeeded in
extracting a living. A similar but narrower belt of land lies at the
eastern base of the Promontory range, and a few others have been found.
In each locality the proximity of subterranean water to the surface is
shown by the success of shallow wells, and there is evidently a natural
irrigation.
There is one region, however, where natural irrigation is out of the
question, but where crops have nevertheless been secured. Bear River
“City” was founded by a company of Danes, who brought the water of the
Malade River to irrigate their fields. After repeated experiment they
became satisfied that the water was so brackish as to be injurious
instead of beneficial, and ceased to use it; and for a number of years
they have obtained a meagre subsistence by dry farming. A district
lying south of Ogden and east of Great Salt Lake, and known as “the
Sand Ridge”, has recently been brought in use, and in 1876 and 1877
winter wheat was harvested with a yield variously reported as from 10
to 15 bushels per acre. This success is regarded by some of the older
settlers as temporary and delusive, for it is said to have depended on
exceptional spring rains; but the majority of the community have faith
in its permanence, and the experiment is being pushed in many valleys.
In Bear River City and on the Sand Ridge water is not found by shallow
wells, and the land is naturally dry. In these localities, and, so
far as I am aware, in all others where dry land has been successfully
farmed, the soil is sandy, and this appears to be an essential
condition. Success has moreover been restricted to the line of valleys
which lie at the western base of the Wasatch Mountains and near Great
Salt Lake.
This last feature depends, as I conceive, on a local peculiarity of
climate. The general movement of the atmosphere is from west to east,
and the air which crosses the lake is immediately lifted from its level
to the crest of the Wasatch. Having acquired from the lake an addition
to its quota of moisture, it has less power of absorption and a greater
tendency to precipitation than the atmosphere in general, and it
confers on the eastern shore of the lake a climate of exceptional
humidity.
The character of this climate is clearly indicated by the assemblage of
the observed facts in regard to precipitation. Through the kindness of
Prof. Joseph Henry I have been permitted to examine the rain records
accumulated by the Smithsonian Institution, including not only those
which have been embodied in the published “Tables,” but the more recent
data to be included in the forthcoming second edition. The following
table shows the mean annual precipitation for all stations in Utah,
Nevada, Wyoming, and Colorado, which have a record two years or more
in extent, together with certain other facts for comparison. The
temperature means are taken from the Smithsonian Temperature Tables and
the United States Signal Service Reports.
+-------------------------+-------+------------+------+-----+---------+
| | | Mean | | | |
| | Annual|Temperature.|Height| | Length |
| Station. |precip-|------+-----|above |Lati-| of |
| | ita- |Spr- |Sum- | sea. |tude.| record. |
| | tion. | ing. | mer.| | | |
+-------------------------+-------+------+-----+------+-----+---------+
| |Inches.| Deg. F. | Feet.| ° ´|Yrs. Mos.|
|Salt Lake City, Utah | 24.81 | 50 | 74 | 4,354|40 46| 9 2 |
|Camp Douglas, Utah | 18.82 | 49 | 73 | 5,024|40 46| 10 3 |
|Colorado Springs, Colo | 17.59 | 44 | 68 | 5,970|38 49| 3 0 |
|Camp Winfield Scott, Nev | 17.33 | 47 | 74 | -- |41 34| 2 8 |
|Fort Massachusetts, Colo | 17.23 | -- | -- | 8,365|37 32| 5 1 |
|Golden City, Colo | 17.01 | -- | 72 | 5,240|39 44| 2 3 |
|Fort Sedgwick, Colo | 15.44 | 47 | 74 | 3,600|40 58| 2 1 |
|Fort Fred. Steele, Wyo | 15.38 | 41 | 66 | 6,845|41 47| 5 5 |
|Fort Fetterman, Wyo | 15.10 | 41 | 67 | 5,012|42 50| 5 7 |
|Fort Garland, Colo | 14.86 | 43 | 64 | 7,864|37 25| 13 1 |
|Fort Laramie, Wyo | 14.45 | 47 | 73 | 4,472|42 12| 17 8 |
|Fort D. A, Russell, Wyo | 14.09 | 36 | 64 | 6,000|41 12| 5 1 |
|Denver, Colo | 13.77 | 46 | 69 | 5,250|39 45| 5 1 |
|Harrisburg, Utah | 13.74 | -- | -- | 3,275|37 10| 2 2 |
|Fort Reynolds, Colo | 13.26 | 52 | 75 | 4,300|38 12| 2 8 |
|Fort Lyon, Colo | 12.56 | 51 | 77 | 4,000|38 08| 7 9 |
|Fort Sanders, Wyo | 11.46 | 38 | 62 | 7,161|41 17| 6 10 |
|Saint George, Utah | 11.39 | -- | -- | 2,800|37 13| 2 11 |
|Camp Halleck, Nev | 10.98 | 45 | 68 | 5,790|40 49| 5 8 |
|Cheyenne, Wyo | 10.14 | 40 | 66 | 6,075|41 08| 3 9 |
|Camp McDermitt, Nev | 8.53 | 46 | 70 | 4,700|41 58| 6 4 |
|Fort Bridger, Wyo | 8.43 | 39 | 63 | 6,656|41 20| 12 10 |
|Fort Churchill, Nev | 7.43 | 52 | 75 | 4,284|39 17| 3 9 |
|Camp Floyd, Utah | 7.33 | 49 | 74 | 4,867|40 16| 2 6 |
| +-------+------+-----+------+-----+---------+
| Means | 13.80 | 45 | 70 | 5,300|40 05| -- |
+-------------------------+-------+------+-----+------+-----+---------+
Two of the stations, Salt Lake City and Camp Douglas, lie within the
zone of climate modified by Great Salt Lake, and a brief inspection
of the table will show how greatly their climate is influenced. As a
general rule, the localities of greatest precipitation in the Rocky
Mountain Region have so great altitude that their summer temperature
does not permit agriculture, but Salt Lake City, with an altitude
1,000 feet below the average of the 24 stations, and a temperature 4°
above the average, has a rainfall 11 inches greater than the average;
and Camp Douglas, 3° warmer than the average and 250 feet lower, has
a rainfall 5 inches greater. If the two stations are compared with
those which lie nearest them, the contrast is still more striking. Camp
Halleck, 130 miles west of the lake, and 600 feet higher than Camp
Douglas, has a rainfall of 11 inches only. Fort Bridger, 90 miles east
of the lake and 1,600 feet higher than Camp Douglas, has a rainfall of
8 inches. Camp Floyd, 30 miles south of the lake and sheltered from its
influence by mountains, receives only 7¹⁄₃ inches. But Salt Lake City
and Camp Douglas, lying between the lake and the Wasatch Range, record
respectively 24.8 and 18.8 inches.
In fine, it appears that the climate of the eastern shore of Great Salt
Lake is decidedly exceptional and approximates in humidity to that of
Central Kansas. The fact that it admits of dry farming gives no warrant
for the belief that large areas in the Arid Region can be cultivated
without irrigation, but serves rather to confirm the conclusion that
the limit to remunerative dry farming is practically drawn by the
isohyetal line of 22 inches. Even in this most favored district the
yield is so small that it can be doubled by irrigation, and eventually
water ditches will be carried to nearly all the land that has yet been
plowed.