Popular Science Monthly/Volume 36/February 1890/Rainfall on the Plains
| RAINFALL ON THE PLAINS. |
By STUART O. HENRY.
THE general impression seems to be that the rainfall has increased and is increasing on our "plains" because of their settlement and cultivation. It is fancied that, as the population moves westward, augmented precipitation follows, so that there is now sufficient rain where ten or twenty years ago it was too dry. Travelers who ride swiftly across this region in a day find towns and catch glimpses of farming operations where five years ago they saw but a barren waste. They conclude that a marked climatic change has taken place, and infer that it can only be due to the presence of population. They fancy that the cultivation of the land must produce marked hygrometric results. That this is a remarkable fallacy becomes certain when attention is called to the evidence.
In the first place, neither history nor science gives any testimony to show that the tillage of the soil and the planting of trees have any appreciable, to say nothing of a considerable, effect on the climate. Even in irrigated countries only a barely perceptible increase in the rainfall has been discovered. In Spain, France, and Italy, irrigation is now not only required for farming, but it is more widely practiced than ever before; yet, if the "rain-belt" theory were correct, these countries would long ago have had sufficient precipitation for successful agriculture. There is scarcely any rainfall in the valley of the Nile to-day, after centuries of cultivation and of annual floods.
Our "plains," or arid region, lie east of the Rocky Mountains, and are at least four hundred miles across. Although the precipitation gradually decreases as one proceeds westward from the Missouri River, it is difficult to fix an isohyetal line. But the line is somewhere between one hundred and two hundred miles west of the Missouri, as the flora clearly shows. It seems to have been taken for granted that the plains were treeless and well-nigh grassless because of lack of rain. Whether the absence of trees is ascribable to the pulverulence of their soil, or the germless lacustrine deposit which covers them, or the excess of moisture, or the fires of the Indians, it is clear that it is not due to rainlessness, because the dry hill-tops in the midst of the arid region have some trees. In other words, there is no evidence whatever that the precipitation on the plains to-day is any greater than it was fifty or one hundred years ago; and there is every reason to believe that it is less.
But, it is said, the observations west of the Missouri show a material increase in the rainfall. This is not true. In the reports of the Kansas State University and the Kansas State Agricultural College we learn that the rainfall for the ten years from 1879 to 1888 is not so great as that of the previous decade. One authority on the subject has recently taken, among other series, the observations at Fort Leavenworth from 1837 to 1883, and, testing by the proper mathematical processes their variabilities and probabilities, demonstrates that there is no indication whatever of permanent climatic change. Yet Fort Leavenworth is one hundred and fifty miles east of the eastern line of the dry region.
It must appear irrational to any one, after a moment's reflection, that the settlement of five or six thousand people in a county usually twenty-four by thirty-six miles in dimensions, and the tillage of a small part of its area, would so materially increase the rainfall in the brief period of ten or twenty years as to make agriculture successful and profitable where before it was not possible. Extending these limits to the wide expanse of States does not make the idea any more tenable. Yet on such conditions as these the theory as applied to our plains is based. The reports of the Nebraska and Kansas Boards of Agriculture will show that, in the territory lying west of the ninety-eighth meridian in those States, the acreage of land actually under cultivation, when compared with the whole area of that territory, is almost insignificant. The climate, as well as the law, pays no heed to small things.
It would not answer for the advocates of the theory only to claim that precipitation would be augmented somewhere, and not necessarily in the certain region where is found the increase of farmed lands; for it would then be very reasonable to suppose that the prevailing southwest and west winds of the plains would drive from them the moisture which the farmer there had earned. Iowa, Missouri, and eastern Kansas, instead of the dry region, would get the increased rainfall.
Prof. Frank H. Snow, of the Kansas State University, said several years ago: "But the fact that thousands of new-comers, from ignorance of the climate, have attempted to introduce ordinary agricultural operations upon the so-called plains, and have disastrously failed in the attempt, has placed an undeserved stigma upon the good name of Kansas in many far-distant communities, and has undoubtedly somewhat retarded immigration during the past few years. It is time for the general recognition of the fact that, except in the exceedingly limited area where irrigation is possible, the western third of Kansas is beyond the limit of successful agriculture." The severe seasons of drought which have occurred since the above conservative statement was written show the whole truth of the matter to be that the westward advancing line of settlement is by no means an isohyetal one, but that it is merely a line representing in a way the overflow of the population of our Eastern States. It needs but a slight acquaintance among the old settlers in central Kansas to know that they fear nowadays excessively dry weather as much as they did twenty-five years ago. The people who live farther west are losing faith in the idea of an increased rainfall, as is evidenced by the fact that over two hundred linear miles of main canals have lately been constructed for irrigation purposes nearly as far east as Kinsley, in the Arkansas Valley of western Kansas. In the Platte Valley, in Nebraska, large irrigating systems are at present being projected.
He who would provide the plains with an ample precipitation must remove the Rocky Mountains. Is it reasonable to suppose that three or four telegraph lines, small bunches of stripling trees here and there, and the turning over of a few thousand acres of sod, can be of any avail in changing a great dry territory into a garden? Can man so easily control Nature and her laws? Certainly not. Climates are immutable so far as the puny efforts of humanity are concerned. And it is a grave fallacy, for on the strength of it hundreds of families are induced each year to locate on the plains with the expectation of farming successfully. Failure follows, of course, and their only hope is to sell out to trustful newcomers, and move where the natural conditions are favorable to agriculture and the prosperity of farm-homes.
