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.

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.

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.

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.