San Juan river forms a short section of the northeastern boundary of the Navaho country, and this is practically the only perennial stream to which they have access.  It is of little use to them, however, as there are no tributaries from the southern or reservation side, other than the Chaco and Chelly “rivers,” which are really merely drainage channels and are dry during most of the year.  The eastern slope of the mountain range gives rise to no streams, and the foot of the range on that side is as dry and waterless as the valley itself.  One may travel for 20 miles over this valley and not find a drop of water.  Except at Sulphur springs, warm volcanic springs about 30 miles south of the San Juan, the ordinary traveler will not find sufficient water between the foot of the mountains and the river, a distance of over 50 miles.  Such is the character of Chaco valley.  But the Indians know of a few holes and pockets in this region which yield a scanty supply of water during parts of the year, and somewhere in the vicinity of these pockets will be found a hogan or two.

Chaco wash or river, like most of the large drainage channels of this country, has a permanent underflow, and by digging wells in the dry, sandy bed it is often possible to obtain a limited supply of water.  This is well known to the Navaho, and 90 per cent of the houses of this region are located within reach of the wash, whence the supply of water which the Navaho deems essential is procured.

On the western slope of the mountains and in the canyons and cliffs of the high table-lands which form the western part of the reservation, the water supply, while still scanty, is abundant as compared with the eastern part.  In the mountains themselves there are numerous small streams, some of which carry water nearly all the year; while here and there throughout the region are many diminutive springs almost or quite permanent in character.  Most of the little streams rise near the crest of the mountains and, flowing westward, are collected in a deep canyon cut in the western slope, whence the water is discharged into Chinlee valley, and traversing its length in the so-called Rio de Chelly, finally reaches San Juan river.  But while these little streams are fairly permanent up in the mountains, their combined flow is seldom sufficient, except in times of flood, to reach the mouth of Canyon Chelly and Chinlee valley.  However, here, as in the Chaco, there is an underflow, which the Indians know how to utilize and from which they can always obtain a sufficient supply of potable water.

The whole Navaho country lies within what the geologists term the Plateau region, and its topography is dictated by the peculiar characteristics of that area.  The soft sandstone measures, which are its most pronounced feature, appear to lie perfectly horizontal, but in fact the strata have a slight, although persistent dip.  From this peculiarity it comes about that each stratum extends for miles with an unbroken sameness