With leave of court (283 U.S. 801, 51 S.Ct. 559, 75 L.Ed. 1423), the state of Washington filed a bill of complaint on July 22, 1931, in which it charged that the state of Oregon as wrongfully diverting the waters of the Walla Walla river to the prejudice of inhabitants of Washington, and prayed an adjudication apportioning the interests of the two states in the river and in tributary streams and restraining any use or diversion of the waters found to be unlawful. To this complaint Oregon filed an answer containing denials and defenses, to which Washington replied. On February 20, 1933, this court appointed a special master with authority to take evidence and with directions to make findings of fact and conclusions of law to be submitted to the court with recommendations for a decree. 288 U.S. 592, 53 S.Ct. 399, 77 L.Ed. 971. The case is now here upon exceptions filed by Washington to the master's report, which finds the facts fully and advises the dismissal of the bill.
The Walla Walla river, a nonnavigable stream, rises in the Blue Mountains of Northeastern Oregon. For about four miles above the city of Milton it flows through a narrow canyon; the waters for that reach being inaccessible for purposes of irrigation. At Milton the river broadens out in a delta formation. The first division in this formation is at Red Bridge, near the city, where the river breaks into two branches. One, the Tum-a-lum, as it is known in Oregon, or the main Walla Walla, as it is known in Washington, flows through cobble rocks over great depths of gravel till it reaches the McCoy Bridge. There, at the margin of an alluvial fan, springs rise from below the surface, and feed the flow anew. Thus reinforced, the stream moves northwesterly to the line between the two states, and again northwesterly for about 30 miles in Washington to its confluence with the Columbia river. A second branch of the river, starting at the Red Bridge, is known as the Little Walla Walla, which divides after a mile into the Crocket and the Ford. Prongs of the Crocket which contribute little, if any, water during the irrigation season, combine with another stream after crossing the state line, and discharge into the main river above the intake of the canal of the Gardena project. Another prong of the Crocket comes together with the Ford and joins the main river in Washington below the intake of the canal. Still another tributary, known as the Mill creek, rises in the Blue Mountains and flows far to the east of the courses just described. After breaking up into other creeks (the Yellowhawk, the Garrison, and others), it joins the main stream of the Walla Walla within the state of Washington. No claim is made by the complainant that the waters of Mill creek have been illegally diverted. Indeed, the fact appears to be that the inhabitants of Washington use the waters of that creek to the exclusion of any use thereof by the inhabitants of Oregon. The claim of wrongdoing has its center in the use of the waters of the Walla Walla arising above the Red Bridge.
The Walla Walla Basin has a emiarid climate with warm dry summers and cold wet winters. The streams contributing to the river are supplied in the main from the snows of the Blue Mountains. Upon the coming of spring, these snows are melted, and the river at that season attains its highest flow. Even then there are variations, not only from month to month, but from day to day. With the advance of summer, the flow diminishes greatly, particularly in the latter part of July and August. In such a climate agriculture cannot go on successfully without the aid of irrigation. A sporadic supply of water will not meet the farmer's needs. 'To be available in a practical sense, the supply must be fairly continuous and dependable.' Wyoming v. Colorado, 259 U.S. 419, 471, 42 S.Ct. 552, 560, 66 L.Ed. 999. A fair division of the water is thus vital to the prosperity of this agriculatural community, and even to its life, for agricultural in the main it is. True, there are cities also within the limits of the watershed, Walla Walla in Washington, with a population of 15,976; Milton and Freewater in Oregon, with a combined population of 2,308. Even so, the welfare of the cities is closely bound up with that of the area about them. Indeed, there has been a unity of growth in the development of the whole community, a development quite independent of the dividing line between the states. As already pointed out, farmers in Washington have had the benefit of Mill creek, which takes its rise in Oregon.