. Bulletin. Ethnology. 12 BUREAU OF AMERICAN ETHNOLOGY [BULU 120 deserts of the Colorado drainage in southern Nevada receive under 5 inches ( at Las Vegas). (See map, fig. 3.) Mountain ranges not only capture but retain greater precipitation. As more than half of the annual precipitation generally falls in win- ter throughout most of the area, it is retained as snow on high moun- tain summits until well into summer (the Sierra of California even have small glaciers) and is released gradually in springs and streams. The run-off of mm^ ^W^$: 5;.:S;;:;V,.j â¢â â â¢â¢'^=* â â ,:â¢/.;
. Bulletin. Ethnology. 12 BUREAU OF AMERICAN ETHNOLOGY [BULU 120 deserts of the Colorado drainage in southern Nevada receive under 5 inches ( at Las Vegas). (See map, fig. 3.) Mountain ranges not only capture but retain greater precipitation. As more than half of the annual precipitation generally falls in win- ter throughout most of the area, it is retained as snow on high moun- tain summits until well into summer (the Sierra of California even have small glaciers) and is released gradually in springs and streams. The run-off of mm^ ^W^$: 5;.:S;;:;V,.j â¢â â â¢â¢'^=* â â ,:â¢/.;â :y!7-:. moisture, how- ever, depends upon mountain structure. A range which is a bal- anced anticlinehas equal run-off on opposite sides. Many ranges, however, are mon- oclines, having one steep escarpment, one gradual dip. On the escarpment the drainage area is small and the moisture flows down the steep rock face, much of it sinking under the thick alluvial deposits which form valley floors without emerging as springs. The opposite side not only has a gentler slope and hence greater drainage area, but the moisture runs along the surface of the strata to emerge here and there as springs. Consequently, one side of these long axial ranges in Nevada may be favored with many sources of water, while the opposite side is comparatively arid. As water is essential for loca- tion of camps, the population tends to cluster predominantly along one side of a range. Thus, the Toyabe Range drains predominantly into Reese River Valley, where the population was relatively dense, while Great Smoky Valle)^ was arid, with few villages. Valleys which are bounded on both sides by escarpments may have a very sparse population. FiQDRB 3.âMap of rainfaU Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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