GRANDE RONDE AND WALLOWA RIVERS.
Grande Ronde River end its principal tributary, the Wallowa, rise in the Blue and Wallowa mountains. Wallowa River drains a portion of the highest and ruggedest mountains in Oregon, nceiving as high a precipitation as many portions of the Cascades. The fertile Wallowa valley nestling at the foot of the towering mountains is irrigated from the tributaries of the river of the same name. This valley s of only limited extent compared with its abundant water supply and probably not over one-fourth of the Wallows’s total dicharge can ever be utilfred. The Grande Ronde likewise is a large river, and with storage, the whole Grande Ronde valley of over one hundred thousand acres can doubtless be thoroughly watered. The total average runoff of Grande Ronde River above the Wallowa is 572,000 acre-feet of which it is estimated that 350,000 can be used in irrigation.
WALLA WALLA RIVER.
Walla Walla River flows through one of the oldest and richest irrigated areas in Oregon. The section is that around the towns of Milton and Freewater. This district, justly famous for strawberries and other horticultural products, has been developed more nearly to its full justifiable extent than any of the areas so far considered. There are at least 6000 acFes under present canals. Little exact information is at hand as to the total water supply, utilized or otherwise, of this district, but as a rough approximation it has been taken as 200,000 acre-feet, with 60,000 capable of irrigation use.
UMATILLA RIVER.
The Umatilla River district, favored of location, soil and climate, is at a disadvantage on account of the insufficient reservoir capacity existing. A few storage basins, of limited capacity have been developed or planned along the river itself. Other reservoirs are found on tributary streams, into which the waters of the main river can be diverted by feed canals, as is the case of Cold Springs Reservoir of the U. S. Reclamation Service.. Spring and winter flood irrigation is also practiced and its further development contemplated. This is particularly successful on the deep volcanic ash soils of the bench lands, which are very retentive of moisture.
As there are no large reservoir sites susceptible of cheap construction, the ultimate utilization of the waters of Umatilla River will probably be a little in excess of the runoff of a low year, say 350,000 acre-feet.
