The same winter maximum of rainfall is characteristic of the whole Pacific coast. The Region of the Lower Columbia, with an average rainfall of 46 inches, receives 47 per cent. of it in winter and 24 per cent. in spring. Southward on the coast, Drum Barracks (near Los Angeles) and San Diego receive more than half their rain in winter, but as the whole amount is only 9 inches agriculture is not benefited. The eastern bases of the Sierra Nevada and Cascade Range exhibit the winter maximum of rainfall, and this feature can be traced eastward in Idaho and Nevada, but in these districts it is accompanied by no amelioration of winter temperature. (See [Table X.])
Table X.—Seasonal precipitation and temperatures on the Pacific coast, etc.
| Station. | Mean annual rainfall. | Percentage of rainfall. | Mean temperature. | ||||
|---|---|---|---|---|---|---|---|
| Inches. | Spring. | Summer. | Autumn. | Winter. | Spring. | Winter. | |
| San Francisco Region | 15.90 | 25 | 1 | 14 | 60 | 57 | 50 |
| Region of Lower Columbia | 46.45 | 24 | 6 | 23 | 47 | 51 | 40 |
| Drum Barracks, Cal | 8.74 | 26 | 3 | 4 | 67 | 60 | 56 |
| San Diego, Cal | 9.31 | 20 | 4 | 20 | 56 | 60 | 54 |
| Camp Independence, Cal | 6.60 | 17 | 5 | 9 | 69 | 57 | 39 |
| Fort Bidwell, Cal | 20.23 | 24 | 8 | 15 | 53 | 48 | 32 |
| Camp Warner, Oreg | 14.41 | 30 | 8 | 17 | 45 | 42 | 29 |
| Camp Harney, Oreg | 8.76 | 26 | 13 | 18 | 43 | 47 | 27 |
| Fort Colville, Wash | 14.06 | 26 | 22 | 18 | 34 | 45 | 24 |
| Fort Walla Walla, Wash | 19.36 | 24 | 11 | 26 | 39 | 52 | 34 |
| Camp McDermitt, Nev | 8.53 | 35 | 9 | 13 | 43 | 46 | 29 |
| Camp Halleck, Nev | 10.98 | 33 | 11 | 21 | 35 | 45 | 28 |
| Fort Lapwai, Idaho | 14.89 | 28 | 16 | 23 | 33 | 53 | 33 |
| Fort Boisé, Idaho | 15.48 | 33 | 8 | 16 | 43 | 52 | 30 |
Third District.—In Arizona and New Mexico there is a general maximum of rainfall in summer, and a restricted maximum in winter. The principal minimum is in spring. In [Table XI] the stations are arranged according to longitudes, a disposition well suited to exhibit their relations. In eastern New Mexico the distribution of rainfall has the same character as in adjacent Texas, but with a more decided maximum. Half of the total rainfall is in summer and half of the remainder in autumn. Westward the maximum diminishes slightly, but it appears in every station of the two territories. In western Arizona the winter maximum of the Pacific coast asserts itself, and it can be traced eastward as far as Fort Wingate, New Mexico. Except at Camp Mohave, on the western border of Arizona, it is inferior in amount to the summer maximum.
Table XI.—Seasonal precipitation in Arizona and New Mexico.
| Station. | Longitude. | Mean annual rainfall. | Percentage of annual rainfall. | |||
|---|---|---|---|---|---|---|
| ° ´ | Inches. | Spring. | Summer. | Autumn. | Winter. | |
| Western Texas | — | — | 19 | 36 | 31 | 14 |
| Fort Union, N. Mex | 104 57 | 19.15 | 11 | 62 | 20 | 7 |
| Cantonment Burgwin, N. Mex | 105 30 | 8.65 | 18 | 34 | 28 | 20 |
| Fort Stanton, N. Mex | 105 38 | 20.94 | 14 | 51 | 23 | 12 |
| Santa Fé, N. Mex | 106 02 | 14.91 | 14 | 46 | 23 | 17 |
| Albuquerque, N. Mex | 106 38 | 8.11 | 10 | 54 | 25 | 11 |
| Fort Fillmore, N. Mex | 106 42 | 8.42 | 5 | 50 | 36 | 9 |
| Fort Selden, N. Mex | 106 55 | 8.49 | 7 | 57 | 22 | 14 |
| Fort Craig, N. Mex | 107 00 | 11.06 | 6 | 53 | 31 | 10 |
| Fort McRae, N. Mex | 107 03 | 11.59 | 21 | 53 | 20 | 6 |
| Fort Wingate, N. Mex | 107 45 | 17.32 | 11 | 38 | 20 | 31 |
| Fort Bayard, N. Mex | 108 30 | 14.32 | 11 | 50 | 16 | 23 |
| Fort Defiance, Ariz | 109 10 | 14.21 | 14 | 42 | 26 | 18 |
| Camp Bowie, Ariz | 109 30 | 15.26 | 9 | 48 | 13 | 30 |
| Camp Grant, Ariz | 110 40 | 15.08 | 14 | 41 | 22 | 23 |
| Camp McDowell, Ariz | 111 36 | 11.45 | 10 | 42 | 15 | 33 |
| Camp Verde, Ariz | 111 54 | 10.85 | 12 | 43 | 22 | 23 |
| Camp Whipple, Ariz | 112 20 | 19.28 | 20 | 42 | 11 | 27 |
| Camp Mohave, Ariz | 114 36 | 4.65 | 18 | 27 | 20 | 35 |
| San Francisco Region | — | — | 25 | 1 | 14 | 60 |
In all this region the daily range of temperature is great, and frosts occur so early in autumn that no use can be made of the autumnal rainfall. The yearly precipitation is very small, and the summer quota rarely exceeds seven or eight inches. Nevertheless the Pueblo Indians have succeeded, in a few localities, and by a unique method, in raising maize without irrigation. The yield is too meagre to tempt the white man to follow their example, and for his use the region is agricultural only where it can be watered artificially.
CHAPTER IV.
WATER SUPPLY.
By G. K. Gilbert.
The following discussion is based upon a special study of the drainage-basin of Great Salt Lake.