Forest physiography; physiography of the United States and principles of soils in relation to forestry . Fig. 21.—The average annual humidity of the air in the United States. I20 FOREST PHYSIOGRAPHY rainfall of the Willamette Valley varies from 25 inches in the southto 45 inches in the north; while the Puget Sound region has an averagerainfall of about 45 inches. The precipitation increases rapidly east-ward as the winds ascend the western slopes of the Sierra Nevada andthe Cascades. It reaches a maximum of about 100 inches in Wash-ington and Oregon, and from 40 to 80 inches in California at e
Forest physiography; physiography of the United States and principles of soils in relation to forestry . Fig. 21.—The average annual humidity of the air in the United States. I20 FOREST PHYSIOGRAPHY rainfall of the Willamette Valley varies from 25 inches in the southto 45 inches in the north; while the Puget Sound region has an averagerainfall of about 45 inches. The precipitation increases rapidly east-ward as the winds ascend the western slopes of the Sierra Nevada andthe Cascades. It reaches a maximum of about 100 inches in Wash-ington and Oregon, and from 40 to 80 inches in California at elevationsbetween 3500 and 5000 feet. Beyond this point the precipitation 125° 121° 117° 113° 109 1H5 101° 97° 93. Fig. 22. — Percentage of annual rainfall received in the six warmer months, April toSeptember inclusive. diminishes again toward the summit and becomes insignificant at theeastern base of the mountains. The great height and continuity of the Sierra Nevada and the Cascadescause these mountains thoroughly to obstruct the westerly winds inrespect of moisture, with the result that great stretches of country eastof them are arid wastes. Where ranges of exceptional height occur inthe country east of the Cascades and the Sierra Nevada the rainfall mayexceed 25 inches a year, but by far the greater part of the region hasless than 12 inches a year. Southwestern Arizona and southern Cali-fornia are the driest regions in the United States, and the rainfall of thelowlands is almost wholly confined to the winter months. In the rainshadow of the Sierra Nevada the mean annual rainfall is between 5 and6 inches and locally as low as 3 inches. It is characteristic of the region PHYSIOGRAPHIC, CLIMATI
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
