Page:Report of the Oregon Conservation Commission to the Governor (1908 - 1914).djvu/270



Irrigation.
Oregon is divided broadly by the Cascade Ran^ into two portions, having widely different characteristics. The western portion is well watered, as it receives a heavy rainfall which furnishes a large runoff to the streams. In the eastern part of the State, on the other hand, there is as a rule a deficiency of moisture.

EASTERN OREGON.
The average precipitation in Eastern Oregon ranges from 8 to 15 or 20 inches and there are only three general localities where there is a large excess of water which in all probability cannot be eventually stored, diverted and used for irrigations. These are lower Deschutes River, lower Klamath River and the streams entering the lower portion of Grande Ronde River from the Wallowa and Blue Mountains. All of these streams receive their waters at too low a level to permit their diversion onto agricultural lands.

In practically all the rest of Eastern Oregon there is more land that can be covered with canal lines than there is water to irrigate it. In Eastern Oregon there are a large number of storage reservoirs, practically every drainage basin including one or more, and in only a few instances will they be of insufficient size to control the entire runoff.

WESTERN OREGON.
West of the mountains, as has been stated there is a heavy runoff, but as a rule it is not distributed throughout the year in a manner to be of the highest utility for irrigation. The streams are all subject to enormous floods in the winter season, from November to March, while the low water period coincides with that of maximum demand of growing crops for moisture.

Storage reservoir sites are limited in number and capacity and for the most part lie too near the heads of the stream courses to be of the greatest value. The amount of water that can be diverted from the tributaries of Willamette River for instance, is limited to the natural runoff during about four months in the summer, and the storage capacity of some six or eight reservoirs.