NEBRASKA v. WYOMING Et Al.

delivered the opinion of the Court.

Nebraska brought this suit in 1934 against Wyoming, invoking our original jurisdiction under Article III, § 2 of the Constitution. 293 U. S. 523. Colorado was impleaded as a defendant. 296 U. S. 553. The United States was granted leave to intervene. 304 U. S. 545. Issues were joined. A Special Master, Honorable Michael J. Doherty, was appointed and hearings were held before him. The matter is before us on exceptions to his report.

I

The controversy pertains to the use for irrigation purposes of the water of the North Platte River, a non-navigable stream. Nebraska alleged that Wyoming and Colorado by diversions of water from the river for irrigation *592 purposes were violating the rule of priority of appropriation in force in the three States and depriving Nebraska of water to which she was equitably entitled. The prayer was for a determination of the equitable share of each State in the water and of the priorities of all appropriations in both States, and for an injunction restraining the alleged wrongful diversions. Wyoming denied the diversion or use of any water to which Nebraska was equitably entitled but joined in the prayer of Nebraska for an equitable apportionment. Colorado filed an answer, together with a cross-bill against Nebraska and Wyoming, which denied any use or threatened use of the water of the North Platte beyond her equitable share, and prayed for an equitable apportionment between the three States, excepting only the tributary waters of the South Platte and Laramie rivers. 1 At the conclusion of Nebraska’s case and again after all the evidence was in, Colorado moved to dismiss the suit on the ground that the evidence was insufficient to sustain any judgment in favor of, or against, any party. Colorado argues here that there should be no affirmative relief against her and that she should be dismissed from the case.

The North Platte River rises in Northern Colorado in the mountainous region known as North Park. 2 It pro *593 ceeds in a northerly direction on the east side of the Continental Divide, enters Wyoming west of Cheyenne, and continues in a northerly direction to the vicinity of Casper. There it turns east across the Great Plains and proceeds easterly and southerly into and across Nebraska. About 40 miles west of the Nebraska line it is joined by the Laramie River. At North Platte, Nebraska, it is joined by the South Platte, forming the Platte River. It empties into the Missouri River at Plattsmouth, near the western border of Iowa. In North Park it is a rapid mountain stream. In eastern Wyoming it gradually broadens out, losing velocity. In western and central Nebraska its channel ranges from 3,000 to 6,000 feet; it frequently divides into small channels; and in times of low water is lost in the deep sands of its bed. Here it is sometimes characterized as a river “two miles wide and one inch deep.”

There are six natural sections of the river basin: (1) North Park, Colorado, or more accurately Jackson County; (2) Colorado-Wyoming line to the Pathfinder Reservoir located between Rawlins and Casper, Wyoming; (3) Pathfinder Reservoir to Whalen, Wyoming, which is 42 miles from the Nebraska line; (4) Whalen, Wyoming to the Tri-State Dam in Nebraska near the Wyoming-Nebraska line; (5) Tri-State Dam to the Kingsley Reservoir, west of Keystone, Nebraska; (6) Kingsley Reservoir to Grand Island, Nebraska. 3

*594 The river basin in Colorado and Wyoming is arid, irrigation being generally indispensable to agriculture. Western Nebraska is partly arid and partly semi-arid. Irrigation is indispensable to the kind of agriculture established there. Middle Nebraska is sub-humid. Some crops can be raised without irrigation. But the lack of irrigation would seriously limit diversification. Eastern Nebraska, beginning at Grand Island, is sufficiently humid so as not to justify irrigation.

Irrigation in the. river basin began about 1865, when some projects were started in eastern Wyoming and western Nebraska. Between 1880 and 1890 irrigation began on a large scale. Until 1909 storage of water was negligible, irrigation being effected by direct diversions and use. Prior to 1909 the development in Calorado and Wyoming was relatively more rapid than in Nebraska. Since 1910 the acreage under irrigation in Colorado increased about 14 per cent, that of Wyoming 31 per cent, and that of Nebraska about 100 per cent. 4 The large increase in Nebraska is mainly attributable to the use of storage water from the Pathfinder Reservoir. 5

The Pathfinder Reservoir is part of the “North Platte Project” which followed the adoption by Congress in 1902 of the Reclamation Act. 32 Stat. 388. Pathfinder was completed in 1913. It has a capacity of 1,045,000 acre *595 feet, which is 79 per cent of the average annual run-off of the North Platte River at that point. This project includes an auxiliary channel reservoir called Guernsey, located above Whalen, Wyoming. Its capacity is 50,870 acre feet. The project also includes two small reservoirs in Nebraska — Lake Alice and Lake Minatare — having a capacity of 11,400 and 67,000 acre feet respectively. There are two main supply canals — Interstate and Fort Laramie — which take out from the North Platte at the Whalen diversion dam. The Interstate canal runs on the north side and the Fort Laramie on the south side of the river. Both extend far into Nebraska. Northport — a third canal — is located wholly in Nebraska. These canals and their laterals extend over 1,600 miles. The project also includes a drainage system and two hydroelectric power plants. The United States contracted with landowners or irrigation districts for use of the water — selling it, as contemplated by the Reclamation Act, so as to recoup the cost of the project which was about $19,000,000: It also entered into so-called Warren Act contracts pursuant to the Act known by that name (36 Stat. 925) which authorized the Secretary of the Interior to contract for the storage and delivery of any surplus water conserved by any reclamation project in excess of the requirements of the project.

We have mentioned the Interstate, Ft. Laramie, and Northport canals which are part of the North Platte Project, the first two of which take out at the Whalen diversion dam. About a mile east of the Wyoming-Nebraska line is the Tri-State Dam. Just above that dam in Nebraska are the headgates of three large Nebraska canals — TriState, Gering, and Northport. Water for the Northport is diverted through the Tri-State headgate, Northport physically being an extension of the Tri-State canal. Another Nebraska canal is the Ramshorn which also receives its supply through Tri-State. Just above the state line is the headgate of the Mitchell canal serving Nebraska land. *596 While these five canals are commonly referred to as the Nebraska State Line Canals, this opinion generally uses the term as excluding Northport which, as we have said, is a North Platte Project canal. There are also nine Wyoming private canals diverting below Whalen. One of these, Erench Canal, serves lands in both Wyoming and Nebraska. The section of the river from Whalen to the Tri-State Dam is the pivotal section of the entire river. In this short stretch of 40-odd miles is concentrated a demand for water as great as in the entire preceding 415 miles apart from the Kendrick project to which we will refer. We will return to a consideration of the problems of this pivotal section shortly.

The North Platte Project has greatly increased the water resources of the river available for irrigation. Unused and wasted water are stored and held over from one season to another. Moreover, the storage water has affected the water tables through saturation of the subsoil. This has increased the return flows available for rediversion and irrigation. The Special Master found that due largely to the influence of the North Platte Project and the application of storage water to lands in eastern Wyoming and western Nebraska the return flows increased from a negligible quantity in 1911 to 700,000 acre feet in 1927. While that amount sharply declined during the drought beginning in 1931, it still is substantial. Thus from 1931-1936 it amounted to 54,300 acre feet in the Whalen-Tri-State Dam section. And as we have already said, the great and disproportionate increase in acreage irrigated in Nebraska since 1910 as compared with the increase in Colorado and Wyoming is largely attributable to the North Platte Project.. While the North Platte Project has increased the water resources, it has complicated the problem of water administration in Wyoming and Nebraska. It has necessitated a segregation of storage and natural flow. The storage plants and diversion works are in Wyoming, although much of the beneficial use is in Nebraska. Appro *597 priators in Nebraska are dependent on regulation and control in Wyoming.

There is a second large federal irrigation project in Wyoming known as the Kendrick project, the estimated cost of which is over $19,000,000. Its primary purpose is the irrigation of some 66,000 acres north and west of Cas-per, Wyoming. The first unit, capable of serving 35,000 acres, was completed in 1940. Due to the lack of water supply it has not yet been put into operation. The second unit is under construction. The storage facilities are completed. They consist of two channel reservoirs — the Seminoe, thirty miles above Pathfinder, with a capacity of 1,026,400 acre feet; the Alcova, thirteen miles below Pathfinder, with a capacity of 190,500 acre feet. Casper Canal will divert the water at Alcova and serve the lands of the project.

The combined storage capacity of the reservoirs of these two federal projects — Kendrick and North Platte — is 2,313,270 acre feet which, as the Special Master found, is 175 per cent of the long-time average annual run-off of the river at Pathfinder.

There are also two projects in Nebraska — Sutherland, with a capacity of 175,000 acre feet, and Tri-County, with a capacity of 2,000,000 acre feet. The latter is expected to bring under irrigation an additional 205,000 acres in Nebraska. Including that acreage but excluding the 60,000 acres expected to be irrigated in Wyoming under the Kendrick project, the Special Master found that the acreages under irrigation in the three .States would be approximately as follows:

Colorado. 131,800 acres (12%)

Wyoming. 325,720 “ (29%)

Nebraska. 653,355 “ (59%)

Total. 1,110,875 (100%)

Prior to the time when the North Platte project went into operation there was a serious shortage of water for *598 irrigation in western Nebraska and to some extent in eastern Wyoming. Many irrigation enterprises were closed. After the North Platte Project had been in operation for awhile most of the projects which had been abandoned were reopened. Prom then until 1931 the supply was reasonably adequate for most of the canals. But the year 1931 started the driest cycle or swing in the North Platte and Platte River valleys of which there is any record. The annual flow at Pathfinder 6 had always fluctuated widely. 7 The average flow for the 37 years commencing in 1904 was 1,315,900 acre feet, the maximum was 2,399,400 in 1917, the minimum was 382,200 in 1934. But a critical condition arose in 1931 with the. advent of the dry cycle. The flow for each of the years between 1931 and 1940 as compared with the mean of the flow for the 37-year period ending in 1940 was as follows:

1931. 55 per cent 1936. 81 per cent

1932. 116 per cent 1937. 87 per cent

1933. 89 per cent 1938. 103 per cent

1934.. 30 per cent 1939. 54 per cent

1935. 54 per cent 1940. 44 per cent

*599 Since 1930 only one year equalled the mean of the 1904 to 1930 period. Previous droughts had not exceeded two or three years. The present cycle has persisted for 13 years.

The commencement of this dry cycle plus the initiation of the Kendrick project precipitated the present controversy. Nebraska rests her case essentially on evidence of shortage and of misappropriation of water by the upper States since 1930 and of threats of more serious shortage and diversions in the future.

II

The equitable apportionment which Nebraska seeks is based on the principle of priority of appropriation applied interstate. Colorado and Wyoming have the rule of priority of appropriation as distinguished from the rule of riparian rights. Colo. Constitution, Art. XVI, §§ 5, 6; Farmers’ High Line Canal Co. v. Southworth, 13 Colo. 111, 21 P. 1028; Sternberger v. Seaton Co., 45 Colo. 401, 102 P. 168; Wyo. Constitution, Art. VIII, § 3; Wyo. Rev. Stat. 1931, §§ 122-401, 122-418, 122-419; Moyer v. Preston, 6 Wyo. 308, 44 P. 845. And see the discussion of the problem in Wyoming v. Colorado, 259 U. S. 419, 459. Nebraska on the other hand was originally a riparian doctrine State. See Meng v. Coffee, 67 Neb. 500, 93 N. W. 713. But when the more arid sections of the State were settled and the need for irrigation increased, legislation was enacted adopting the appropriation principle. See Neb. L. 1889, ch. 68; L. 1895, ch. 69. That principle was recognized in the constitution which Nebraska adopted in 1920. See Article XV, §§ 4, 5, and 6. The adoption of the rule of appropriation did not extinguish riparian rights which had previously vested. See Clark v. Cambridge & Arapahoe Co., 45 Neb. 798, 64 N. W. 239; Crawford Co. v. Hathaway, 60 Neb. 754, 84 N. W. 271, 61 Neb. 317, 85 N. W. 303, 67 Neb. 325, 93 N. W. 781; Osterman v. Central *600 Nebraska District, 131 Neb. 356, 268 N. W. 334. But riparian rights may be condemned in favor of appropriators; and violation of riparian rights by appropriators will not be enjoined, only compensation or damages being awarded. Cline v. Stock, 71 Neb. 79, 102 N. W. 265; McCook Irrigation Co. v. Crews, 70 Neb. 115, 102 N. W. 249. In that sense riparian rights are considered inferior to rights of appropriators. More important, the rights asserted by Nebraska in this suit are based wholly on appropriations which have been obtained and recognized under Nebraska law. The appropriation system is dominant in the regions of Nebraska which are involved in the present litigation. Hence we, like the Special Master, treat the case as one involving appropriation rights not only in Colorado and Wyoming but in Nebraska as well.

North Park. There are at present in the North Park area in Colorado (Jackson County) 131,800 acres irrigated. The climate is arid. The sole industry is cattle raising, the only crops being native hay and pasturage. The growing season is short. While the diversions are high per acre (about 4% acre feet) the return flows are large, making the average consumptive use 8 rate only .74 acre foot per acre. The 131,800 acres of irrigated land consume 98,572 acre feet annually, including reservoir evaporation. Exportations from the basin are expected to average 6,000 acre feet, making the total annual depletion 104,540 acre feet. Though Colorado claimed that an additional 100,000 acres in North Park was susceptible of irrigation, the Special Master found that there are only about 34,000 acres of additional land that could be brought under irrigation; 30,390 of those acres are irrigable from constructed ditch systems having water rights. Those projects, however, are not completed; they are indeed projects for the indefinite future. In addition to these *601 projects in North Park, Colorado also has proposed that large quantities of water from the river be exported from the basin into other rivers.

There have been out-of-priority diversions in Colorado and Wyoming above Pathfinder in relation to the priorities and needs of Nebraska users. Their full extent is not known. But as respects Pathfinder, the Special Master estimated that Colorado appropriators junior to Pathfinder consume about 30,000 acre feet a year. Since Pathfinder after 1930 has never been filled and has always been in need of water for storage, those Colorado junior diversions may be said to have violated the Pathfinder priority. The claims of Colorado to additional demands were construed by the Special Master as a threat of further depletion of the river within North Park. He found that there was no surplus in the supply and that any material increase in diversions in Colorado would be in violation of established priorities, notably Pathfinder.

Colorado Line to Pathfinder Reservoir. In the region between the Colorado-Wyoming line and Pathfinder appropriation rights cover about 272,000 acres, 149,400 of which are irrigated. But of those only 9,400 acres are irrigated from the main stream, the balance being irrigated from tributaries. The consumptive use rate is about 1 acre foot per acre. Over two-thirds of the volume of diversions (main stream and tributaries) and 88 per cent from the main stream are senior to the North Platte Project. They are in the main junior to the State Line Canals in Nebraska. Those projects junior to Pathfinder have been operated since 1930 in violation of its priority. The Special Master found that there is no present prospect of any large expansion of irrigation in this area, though five additional projects have been contemplated, some of them being partially constructed. The accretions to the river from tributaries in this section are very large— about 790,240 acre feet net. Land consumption is 16 per *602 cent of the net accretions, while that of rights junior to Pathfinder is about 5.6 per cent of the net.

North Platte Project. The priority of Pathfinder is December 6, 1904 and of Guernsey April 20, 1923. Between Pathfinder and the Nebraska state line there are 32 canals on the main river which have priorities senior to Pathfinder. The State Line Canals in Nebraska also are senior to Pathfinder. And Guernsey is junior to all canals below it down to the Nebraska line. The percentage of rights in each section senior and junior to the North Platte Project are as follows:

Per- Percentage centage Senior Junior

North Park. 67 33

Colorado State Line to Pathfinder Reservoir. 88 12

Pathfinder Reservoir to Whalen. 52 48

Whalen to Nebraska State Line (Wyoming private canals). 91 9

Nebraska State Line Canals. 100 0

Under Wyoming law reservoirs in storing water must observe the priority of all senior Wyoming canals below them on the main river.

Kendrick Project. Seminoe Reservoir has a priority of December 1, 1931; Casper Canal, July 27, 1934 (natural flow); Alcova Reservoir, April 25, 1936. Apart from minor exceptions Seminoe is junior to every appropriator from Alcova to the Tri-State Dam. The project is expected to operate chiefly on storage water. In its early stages it-s water requirements will be heavier than they will be later, due to ground absorption and storage. When the project has been in operation a while, the depletion during the irrigation season will be about 122,000 acre feet, except as water stored in non-irrigation season is used. The Special Master found, however, that without violating the Pathfinder priority, the Kendrick project could have stored no water since 1930 and can store none in the future if present conditions continue. He also *603 found that under the average conditions which prevailed from 1895 to 1939 water could be conserved by Seminoe and Alcova without violation of the priorities between Pathfinder and Tri-State Dam and in sufficient quantities to supply Kendrick and to leave considerable return flow to the river in the irrigation season. There are in the first unit of the project two sump areas into which return water will flow and from which the United States has constructed drainage ditches so as to return the water to the river. On the uncompleted unit three sump areas are planned. These are designed to return to the river water which otherwise would be lost.

Pathfinder to Whalen. The total land irrigated in this section is in excess of 55,000 acres, of which about 14,000 acres are supplied from the main river. Alfalfa, sugar beets, potatoes, and grains are the principal irrigated crops. There are 60 canals taking out of the main river with priorities ranging from 1887 to 1937. In terms of acreage about 48 per cent of the rights on the river in this section are junior to the North Platte Project. All except one are junior to the Tri-State canal and most of them are junior to the other Nebraska State Line Canals. The irrigation projects on the river average not over 160 acres. The consumptive use rate is about 1.1 acre feet per acre. The diversion rate of 2.5 acre feet per acre is deemed adequate. But during the 1931-1940 period the average seasonal diversion rate for the section was only 2 acre feet, since in low stages of flow some of the ditches are unable to divert any water. But at the rate of 2.5 acre feet the total seasonal headgate diversion for the 14,000 acres is 35,000 acre feet of which 18,200 acre feet would be returned to the river. Of that return all but 15 per cent (2,730 acre feet) would occur during the irrigation season. The tributary inflow is greater than river depletion due to irrigations and other losses. The average annual net gain from 1931-1940 was 64,200 acre feet. During *604 the 1931-1940 period, the maximum seasonal average consumption out-of-priority in relation to the Nebraska State Line Canals was found by the Special Master to be 5,400 acre feet. With probable minor exceptions there are no further possibilities for irrigation developments in this section.

Whalen to Tri-State Dam. As we have said, this is the pivotal section of the river around which the central problems of this case turn. Apart from the Kendrick project, the demand for water is as great in this short section of the river as in the entire preceding 415 miles from North Park to Whalen. The lands irrigated from the river in this section total 326,000 acres as compared with 339,200 acres in the upper valley — main river and tributaries. The consumptive use on this 326,000 acres far exceeds that of the upper sections combined. We have mentioned the various canals which take out from the river in this section. The Special Master found their annual requirements to be 1,072,514 acre feet. The total net seasonal requirement of all the canals diverting in this section was found to be 1,027,000 acre feet. In the ten-year period from 1931 to 1940 this net seasonal requirement of 1,027,000 acre feet largely exceeded the supply in three years and was less than the supply in seven years. 9 In those seven years the seasonal flows passing the TriState Dam were far less than the excesses, indicating as the ■Special Master concluded that canal diversions in the section were greater than the requirements. He pointed out that if the diversions during the period had been re *605 stricted to the determined requirements and if the excess had been held in storage in the upper reservoirs and released indiscriminately to all canals as needed, irrespective of storage rights, any surplus water would have been conserved and would not have passed Tri-State. He estimated that under that method of operation the total supply (excluding any supply for Kendrick) would have been approximately sufficient for the section.

But on the basis of the 1931-1940 supply the seasonal requirement of 1,027,000 acre feet cannot be met by natural flow alone and without storage water. The Special Master roughly estimated the deficiency of natural flow as follows for the period of 1931 to 1940:

Deficiency Tear of natural flow 1

1931.;. 552,952 acre feet

1932. 305,000 “ “

1933. 251,980 “ “

1934. 841,488 “ “

1935. 666,058 “ “

1936. 495,737 “ “

1937. 489,975 “ “

1938. 501,991 “ “

1939. 450,908 “ “

1940 . 751,244 “ “

On that basis the average seasonal supply of natural flow available in this section was only 48 per cent of the total requirement. In 1933, the year of largest flow, it was only 75 per cent. In general the practice has been to allow storage right canals having early priorities to receive natural flow water on a priority basis, using storage water merely as a supplementary supply. In this area 90 per cent of the lands have both natural flow and storage rights. 10 Seventy-eight per cent of the lands having stor *606 age rights are in Nebraska, 22 per cent in Wyoming. Of the lands having natural flow rights only 49 per cent are in Nebraska and 51 per cent in Wyoming.

As respects priority, the canals (listed later in this opinion) fall into thirteen groups, seven in Wyoming and six in Nebraska. The earliest in priority are some canals in Wyoming, then some in Nebraska, then others in Wyoming and so on.

The exceptional features of this section of the river were summarized by the Special Master as follows:

“(1) the great concentration of demand in a short compact section, (2) the presence of water, both natural flow and storage, to which Nebraska users are entitled under Wyoming appropriations, (3) the total dependence of Nebraska State Line Canals and the North Platte project canals upon water originating in Wyoming and Colorado, (4) the joint use of canals to serve both Wyoming and Nebraska lands, (5) the location in Wyoming of the head gates and works which divert great volumes of water for Nebraska, (6) the distinctly interstate scope and character of the water distribution without any real interstate administration.”

The Special Master made a detailed study of the requirements of each canal in this section and the diversions of each during the 1931-1940 period. We need not recapitulate it. The nine Wyoming canals and the TriState canal fared well. A comparison of the average seasonal diversions with the seasonal requirements shows that they had an excess supply for the ten-year period — 122 per cent and 111 per cent respectively — the former having a deficiency in only one of the ten years, the latter a deficiency jn three. For the rest of these canals it appears that the average seasonal diversions supplied from 78 per cent to 98 per cent of their seasonal requirements. The Ft. Laramie was short in eight of the ten years, Gering, Rams-horn and Northport in seven each.

*607 Tri-State Dam to Bridgeport, Neb. Nebraska originally claimed that any equitable distribution which was made should extend to all irrigated lands as far east as Grand Island, Neb. It is now conceded that the lands east of Bridgeport, Neb., which is some sixty miles from the Wyoming-Nebraska state line, can be reasonably satisfied out of local supplies. Hence we are not concerned in this case with that section.

In the section west of Bridgeport, there are twelve canals exclusive of the Ramshorn relevant to the present problem. Their requirements are 132,420 acre feet; their demand on the main river is 102,810 acre feet, the balance being obtained from interceptions of drains, return flows, and tributary streams. The Special Master concluded that local supplies even during the drought period were adequate to take care of the needs of these canals without calling upon up-river water. Some shortages occurred, caused for example by excessive use by some canals at the expense of others or by the withdrawal of water from the section to supply senior canals below. It would seem that the construction and operation of the Kingsley and Sutherland Reservoirs would largely eliminate the latter condition. And water passing Tri-State Dam and usable in the Tri-State to Bridgeport section is substantial — the mean divertible flow for the irrigation season in the 1931-1940 period being 81,700 acre feet. Over half of this occurred in May and June; very little in August and September.

Ill

Motion to Dismiss. As we have noted, Colorado moves to dismiss the proceeding. She asserts that the pleadings and evidence both indicate that she has not injured nor presently threatens to injure any downstream water user. She emphasizes the large increase since 1910 in acreage under irrigation in Wyoming and Nebraska as compared

*608 with the increase in Colorado. She asserts there is a surplus of water in the stream, as evidenced by the fact that during the recent drought or dry cycle the Kendrick Project in Wyoming and the Tri-County Project in Nebraska have been constructed, indicating that the sponsors considered that the available water supply was not entirely used by existing projects. And she emphasizes that during the drought there was a divertible flow passing TriState Dam during the irrigation season. The argument is that the case is not of such serious magnitude and the damage is not so fully and clearly proved as to warrant the intervention of this Court under our established practice. Missouri v. Illinois, 200 U. S. 496, 521; Colorado v. Kansas, 320 U. S. 383, 393-394. The argument is that the potential threat of injury, representing as it does only a possibility for the indefinite future, is no basis for a decree in an interstate suit since we cannot issue declaratory decrees. Arizona v. California, 283 U. S. 423, 462-464, and cases cited.

We fully recognize those principles. But they do not stand in the way of an entry of a decree in this case.

The evidence supports the finding of the Special Master that the'dependable natural flow of the river during the irrigation season has long been over-appropriated. A genuine controversy exists. The States have not been able to settle their differences by compact. The areas involved are arid or semi-arid. Water in dependable amounts is essential to the maintenance of the vast agricultural enterprises established on the various sections of the river. The dry cycle which has continued over a decade has precipitated a clash of interests which between sovereign powers could be traditionally settled only by diplomacy or war. The original jurisdiction of this Court is one of the alternative methods provided by the Framers of our Constitution. Missouri v. Illinois, 180 U. S. 208, 241; Georgia v. Tennessee Copper Co., 206 U. S. 230, 237. The *609 Kendrick Project plainly is an existing threat to senior appropriators downstream. As we have noted, it is junior to practically every appropriation on the river between Alcova and the Tri-State Dam. Since 1930 there would have been no water for it if it were operated on a priority basis. And in view of the general position taken by Wyoming with respect to Nebraska priorities, it cannot be assumed that the Kendrick Project would be regulated for the benefit of senior appropriators in Nebraska. Neither Wyoming nor Colorado has ever recognized any extension of priorities across state lines. They have never limited or regulated diversions by their appropriators in subordination to the senior appropriators of a downstream State. Out-of-priority diversions by Colorado have had an adverse effect downstream. We do not know their full extent; but we do know that Colorado appropriators junior to Pathfinder consume about 30,000 acre feet a year and that Pathfinder has never been filled since 1930 and has always been in need of water. This alone negatives the absence of present injury. The fact that on the average there is some water passing Tri-State Dam unused is no answer. While over half of that excess amount ’occurred in May and June, there was comparatively little in August and September. Moreover, we are dealing here with the problems of natural flow. The critical condition of the supply of the natural flow during 1931-1940 in the Whalen to Tri-State Dam section is obvious. The claim of Colorado to additional demands may not be disregarded. The fact that Colorado’s proposed projects are not planned for the immediate future is not conclusive in view of the present over-appropriation of natural flow. The additional demands on the river which those projects involve constitute a threat of further depletion. Colorado in her argument here asserts that “if Jackson County is to maintain its livestock industry to the same extent as it has in the past it will have to develop this additional summer *610 pasture and it cannot do this without increasing its irrigated acreage.”

What we have then is a situation where three States assert against a river, whose dependable natural flow during the irrigation season has long been over-appropriated, claims based not only on present uses but on projected additional uses as well. The various statistics with which the record abounds are inconclusive in showing the existence or extent of actual damage to Nebraska. But we know that deprivation of water in arid or semi-arid regions cannot help but be injurious. That was the basis for the apportionment of water made by the Court in Wyoming v. Colorado, supra. There the only showing of injury or threat of injury was the inadequacy of the supply of water to meet all appropriative rights. As much if not more is shown here. If this were an equity suit to enjoin threatened injury, the showing made by Nebraska might possibly be insufficient. But Wyoming v. Colorado, supra, indicates that where the claims to the water of a river exceed the supply a controversy exists appropriate for judicial determination. If there were a surplus of unappropriated water, different considerations would be applicable. Cf. Arizona v. California, 298 U. S. 568. But where there is not enough water in the river to satisfy the claims asserted against it, the situation is not basically different from that where two or more persons claim the right to the same parcel of land. The present claimants being States, we think the clash of interests to be of that character and dignity which makes the controversy a justiciable one under our original jurisdiction.

Colorado v. Kansas, supra, is not opposed to this view. That case turned on its special facts. It is true that an apportionment of the water of an interstate river was denied in that case. But the downstream State (Kansas) did not sustain the burden of showing that since the earlier litigation between the States (see Kansas v. Colorado, *611 206 U. S. 46), there had been a material increase in the depletion of the river by Colorado. Improvements based upon irrigation had been made by Colorado while Kansas stood by for over twenty years without protest. We held that in those circumstances a plain showing was necessary of increased depletion and substantial injury to warrant a decree which would disrupt the economy of the upstream State built around irrigation. Moreover, we made clear (320 U. S. p. 392, note 2) that we were not dealing there with a case like Wyoming v. Colorado, supra, where the doctrine of appropriation applied in each of the States which were parties to the suit and where there was not sufficient water to meet all the present and prospective needs.

Colorado’s motion to dismiss is accordingly denied.

IY

Claim of United States to Unappropriated Water. The United States claims that it owns all the unappropriated water in the river. It argues that it owned the then unappropriated water at the time it acquired water rights by appropriation for the North Platte Project and the Kendrick Project. Its basic rights are therefore said to derive not from appropriation but from its underlying ownership which entitles it to an apportionment in this suit free from state control. The argument is that the United States acquired the original ownership of all rights in the water as well as the lands in the North Platte basin by cessions from France, Spain and Mexico in 1803, 1819, and 1848, and by agreement with Texas in 1850. It says it still owns those rights in water to whatever extent it has not disposed of them. An extensive review of federal water legislation applicable to the Platte River basin is made beginning with the Act of July 26, 1866, 14 Stat. 251, the Act of July 9, 1870, 16 Stat. 217 and including the Desert Land Law (Act of March 3, 1877, 19 Stat. 377) *612 and the Reclamation Act of June 17, 1902, 32 Stat. 388. But we do not stop to determine what rights to unappropriated water of the river the United States may have. For the water rights on which the North Platte Project and the Kendrick Project rest have been obtained in compliance with state law. Whether they might have been obtained by federal reservation is not important. Nor, as we shall see, is it important to the decree to be entered in this case that there may be unappropriated water to which the United States may in the future assert rights through the machinery of state law or otherwise.

The Desert Land Act “effected a severance of all waters upon the public domain, not theretofore appropriated, from the land itself.” California Oregon Power Co. v. Beaver Portland Cement Co., 295 U. S. 142, 158. It extended the right of appropriation to any declarant who reclaimed desert land and provided: “all surplus water over and above such actual appropriation and use, together with the water of all, lakes, rivers and other sources of water supply upon the public lands and not navigable, shall remain and be held free for the appropriation and use of the public for irrigation, mining and manufacturing purposes subject to existing rights.” See Ickes v. Fox, 300 U. S. 82, 95; Brush v. Commissioner, 300 U. S. 352, 367.

Sec. 8 of the Reclamation Act provided: “That nothing in this Act shall be construed as affecting or intended to affect or to in any way interfere with the laws of any State or Territory relating to the control, appropriation, use, or distribution of water used in irrigation, or any vested right acquired thereunder, and the Secretary of the Interior, in carrying out the provisions of this Act, shall proceed in conformity with such laws, and nothing herein shall in any way affect any right of any State or of the Federal Government or of any landowner, appropriator, or user of water in, to, or from any interstate stream or the waters *613 thereof: Provided, That the right to the use of water acquired under the provisions of this Act shall be appurtenant to the land irrigated, and beneficial use shall be the basis, the measure, and the li