russell.] GEOLOGY OF SW. IDAHO AND 8E. OREGON. 21 
HYDROGRAPHY. * 
DRAINAGE SLOPES. 
In reference to drainage the portions of Idaho and Oregon traversed 
during the reconnaissance of 1902 present two principal divisions. 
All of the part of Idaho visited, together with Malheur County and 
the northeastern part of Harney County, Oreg., belong to the drain- 
age system of Snake River, a branch of the Columbia, the waters of 
which are discharged into the Pacific Ocean. This region is thus a 
portion of the Pacific slope of North America. The principal part of 
Harney County, however, sends no water to the ocean, but is a part 
of the great region of interior drainage termed the Great Basin. The 
dividing line between these two great hydrographic provinces, in the 
region under review, is indicated by a broken line on the map forming- 
Pi. I. 
STREAMS. 
The principal streams tributary to Snake River are the Owyhee and 
Malheur rivers. The Owyhee rises in the bold mountains of Owyhee 
County, Idaho, and the adjacent region on the west which lies in 
Oregon, and has the same general topography and climate. It flows for 
the most part through a succession of narrow defiles cut in resistant 
igneous rocks, but at times its canyon opens out into park-like valleys 
where soft lacustral sediment permitted easy excavation. One of 
these wide reaches eroded by the stream is situated where Jordan 
Creek joins it. Here there is a beautiful valley about 6 miles long 
and 2 miles wide, the east and west borders of which are picturesque 
cliffs. The rocks are principally evenly stratified lacustral sediments 
of Tertiary age which are light colored and in part of a delicate-green 
tint. Some idea of the marvelous rain and wind sculpture on the bold 
wall of this little stream-eroded basin may be gathered from PI. 
XVIII. The bottom of the valley is sagebrush land, a small portion 
of which is now under irrigation. At the lower end of the valley the 
soft lacustral deposits are absent, and the river has cut a narrow can- 
yon about 200 feet deep with vertical wall through dense igneous rock. 
A favorable site is here furnished for a storage reservoir, in which 
the abundant winter waters of the Owyhee might be retained for use 
on the parched plains near Snake River. This site is certainty worth 
careful investigation by engineers, and as I have been informed by 
settlers in the region, is but one of several similar localities along 
the Owyhee where storage dams might perhaps be constructed to 
a< {vantage. 
The Owyhee River, in the lower portion of its course, after passing 
through a narrow, irregular, steep-sided canyon in the Cedar Moun- 
tains and emerging into the broad valle}^ excavated by Snake River, 
is bordered by flat lands, where the soil is rich. All of its water in 
summer is used for irrigation. 
