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.

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

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

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

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):

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.

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.

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.