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 Although withdrawn from the domain of the unknowable, they remain within that of the unknown.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.
| Rivers, etc. | Measured volume in feet per second. | Estimated mean volume in feet 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.