Laramie Plains served by the greater part of the Wyoming appropriations, a substantial amount of water percolates back into the stream from irrigated areas and becomes available for further use lower down the stream. This is called return water. The amount varies considerably, and there is no definite data on the subject. As respects irrigation on the Laramie Plains above the Wheatland diversion, the evidences satisfies us that the return water will certainly more than counterbalance the loss throughout evaporation and otherwise when the period of storage is not more than from one year to the next.

What has now been said covers the substance of the evidence, as we regard it, bearing on the available supply at Woods and in that vicinity; that is to say, the supply remaining after the recognized Colorado appropriations are satisfied.

We already have indicated that, as to such a stream as this, the average flow of all years, high and low, can not be taken as a proper or reasonable measure of what is available for practical use. What then is the amount which is available here? According to the general consensus of opinion among practical irrigators and experienced irrigation engineers, the lowest natural flow of the years is not the test. In practice they proceed on the view that within limits, financially and physically feasible, a fairly constant and dependable flow materially in excess of the lowest may generally be obtained by means of reservoirs adapted to conserving and equalizing the natural flow; and we regard this view as reasonable.

But Wyoming takes the position that she should not be required to provide storage facilities in order that Colorado may obtain a larger amount of water from the common supply than otherwise would be possible. In a sense this is true; but not to the extent of requiring that the lowest natural flow be taken as the test of the available supply. The question here is not what one State should do for the other, but how each should exercise her relative rights in the waters of this interstate stream. Both are interested in the stream and both have great need for the water. Both subscribe to the doctrine of appropriation, and by that doctrine rights to water are measured by what is reasonably required and applied. Both States recognize that conservation within practicable limits is essential in order that needless waste may be prevented and the largest feasible use may be secured. This comports with the all-pervading spirit of the doctrine of appropriation and takes appropriate heed of the natural necessities out of which it arose. We think that doctrine lays on each of these States a duty to exercise her right reasonably and in a manner calculated to conserve the common supply. Notwithstanding her present contention, Wyoming has in fact proceeded on this line, for, as the proof shows, her appropriators, with her sanction, have provided and have in service reservoir facilities which are adapted for the purpose and reasonably sufficient to meet its requirements.

There is one respect, requiring mention, in which Colorado's situation differs materially from that of Wyoming. The water to satisfy the Colorado appropriations is, and in the nature of things must be, diverted in Colorado at the head of the stream; and because of this those appropriations will not be affected by any variation in the yearly flow, but will receive their full measure of water in all years. On the other hand, the Wyoming appropriations will receive the water only after it passes down into that State, and must bear whatever of risk is incident to the variation in the natural flow. Of course, this affords no reason for underestimating the available supply, but it does show that to overestimate it will work particular injury to Wyo

ming.

The lowest established flow was that of 1913. There is no claim or proof that in any other year the flow fell so low. Had there been others some proof of it doubtless would have been presented. This is also true of the very low flow of 1896. Therefore we think it reasonably may be assumed that the flow of those years was so exceptional that it is not likely to recur save at long intervals.

We conclude, in view of all the evidence and of the several considerations we have stated, that the natural and varying flow of this stream at Woods, which is after the recognized Colorado appropriations are satisfied, is susceptible by means of practicable storage and conservation of being converted into a fairly constant and dependable flow of 170,000 acre-feet per year, but not more. This we hold to be the avail

able supply at that point after the recognized Colorado diversions are made. The amount may seem large, but, considering what may be accomplished with practicable storage facilities, such as are already provided, and the use which may be made of the return water, we are persuaded that the amount, while closely pressing the outside limit, is not too large.

1316-22-PT 1- -4

The problem to be worked out in obtaining a fairly dependable supply in that amount is measurably illustrated by the following table covering all the years for which the evidence supplies the requisite data, the flow during the missing months being fairly estimated:

It of course is true that the variation in the flow will not always be just what it was in the years covered by the table, and yet the data obtained by the gaging and measurements in those years show better than anything else what reasonably may be expected in the future. We recognize that the problem which the table is intended to illustrate is not a simple one and that to work it out will involve the exercise of both skill and care. But in this it is not unlike other problems of similar moment. Our belief gathered from all the evidence is that, with the attention which rightly should be bestowed on a problem of such moment, it can be successfully solved within the limits of what is financially and physically practicable.

As to Sand Creek, Colorado's witness regarded it as a tributary of the river and estimated its yearly flow at 17,000 acre-feet. The creek rises in Colorado, extends into the Laramie Plains in Wyoming, and discharges into Hutton Lake, a few miles from the river. In exceptional years-about one in five-the waters of the creek overflow the lake for a short period and find their way over the prairie into the river, Otherwise the river receives no water from the creek. The proof of this is direct and undisputed. The creek is nominally a tributary of the river, but only that. Besides, its flow does not appear to have been measured. The witness merely estimated it at what he thought would be the natural run-off of the adjacent territory. Other evidence suggests that the estimate is too high, but this we need not consider. A substantial part of the flow is diverted, through what is known as the Divide Ditch, for use in irrigating lands in Colorado, and the evidence suggests, if it does not establish, that existing appropriations in the two States take the entire flow. For these reasons the waters of this creek can not be regarded as a factor in this controversy. After passing Woods, and while traversing the territory wherein are the Wyoming appropriations with which we are concerned, the Laramie receives one large and some very small additions to its waters.

The large addition comes from the Little Laramie, a stream whose source and entire length are in Wyoming. Its natural flow is a little more than one-half of that of the main stream at Woods and is subject to much the same variations. Part of its flow is used under appropriations along its course and the remainder passes into the main stream. Including what is appropriated along its course, and excluding minor contributions by small creeks after it gets well away from its headwaters, we think the amount available for practical use is 93,000 acre-feet per year.

None of the small tributaries, whether of the Laramie or the Little Laramie, adds much to the available supply. Their natural flow is small. As to some it is all used under old appropriations; as to some it is partly used under such appropriations; and as to some it is only seasonal, the channels being dry much of the year. Some creeks spoken of in Colorado's evidence as tributaries are otherwise shown not to be such, but to deliver their waters into lakes or ponds not connected with either of the principal streams. Colorado's evidence also takes into account some tributaries which discharge into the Laramie below the points of diversion of all the Wyoming appropriations with which we are concerned. One, of which much is said in the evidence, is the Sybille. It reaches the Laramie below the diversion for the Wheatland Dis

trict (the lowest diversion we are to consider), but in its course passes through that district. A small part of its flow is used in that district and it is not practicable to use more. What is used should, for present purposes, be treated as if it reached the Laramie above the Wheatland diversion. Wyoming contends that none of these small tributaries, other than the Sybille, contributes any dependable amount to the available supply. We think there is in the aggregate a fairly dependable contribution of 25,000 acre-feet, but not more.

It results that, in our opinion, the entire supply available for the proposed Colorado appropriation and the Wyoming appropriations down to and including the diversion for the Wheatland district is 288,000 acre-feet.

In contending for a larger finding, Colorado points to the issue by Wyoming's State engineer of permits, so-called, for appropriations in excess of that amount and insists that these permits constitute solemn adjudications by that officer that the supply is adequate to cover them. But in this the nature of the permits is misapprehended. In fact and in law they are not adjudications but mere licenses to appropriate if the requisite amount of water be there. As to many nothing ever is done under them by the intending appropriators. In such cases there is no appropriation; and even in others the amount of the appropriation turns on what is actually done under the permit. In late years the permits relating to these streams have contained a provision, saying: "The records of the State engineer's office show the waters of [the particular stream] to be largely appropriated. The appropriator under the permit is hereby notified of this fact, and the issuance of this permit grants only the right to divert and use the surplus of waste water of the stream and confers no rights which will interfere with or impair the use of water by prior appropriators." It therefore is plain that these permits have no such probative force as Colorado seeks to have attributed to them.

Colorado also comments on the amount of water stored in Wyoming reservoirs in 1912 and seeks to draw from this an inference that the available supply was greater than we have indicated. But the inference is not justified, and for these reasons: First, a part of what was stored was dead water; that is, was below the level from which water could be drawn off and conducted to the places of use. This is a matter commonly experienced in the selection and use of reservoir sites. Secondly, the flow of 1912 was above what could be depended on and prudence required that a substantial part be carried over to meet a possible shortage in the succeeding year. And, thirdly, the evidence shows that in 1912 the storing process was improvidently carried to a point which infringed the rights of small appropriators who were without storage facilities.

The available supply the 288,000 acre-feet-is not sufficient to satisfy the Wyoming appropriations dependent thereon and also the proposed Colorado appropriation, so it becomes necessary to consider their relative priorities.

There are some existing Colorado appropriations having priorities entitling them to precedence over many of the Wyoming appropriations. These recognized Colorado appropriations are, 18,000 acre-feet for what is known as the Skyline Ditch and 4,250 acre-feet for the irrigation of that number of acres of native-hay meadows in the Laramie Valley in Colorado, the 4,250 acre-feet being what Colorado's chief witness testifies is reasonably required for the purpose, although a larger amount is claimed in the State's answer. These recognized Colorado appropriations, aggregating 22,250 acrefeet, are not to be deducted from the 288,000 acre-feet, that being the available supply after they are satisfied. Nor is Colorado's appropriation from Sand Creek to be deducted, that creek, as we have shown, not being a tributary of the Laramie.

The proposed Colorado appropriation which is in controversy here is spoken of in the evidence as the Laramie-Poudre Tunnel diversion and is part of an irrigation project known as the Laramie-Poudre project. Colorado insists that this proposed appropriation takes priority, by relation, as of August 25, 1902, and Wyoming that the priority can relate only to the latter part of 1909. The true date is a matter of importance, because some large irrigation works were started in Wyoming between the dates mentioned, were diligently carried to completion, and are entitled to priorities as of the dates when they were started.

In

The Laramie-Poudre project is composed of several units, originally distinct, which underwent many changes before they were brought together in a single project. its final form the project is intended to divert water by means of a tunnel from the Laramie River into the Poudre watershed, there to unite that water with water taken from the Cache la Poudre River and then to convey the water many miles to the lower part of the Poudre Valley, where it is to be used in reclaiming and irrigating a body of land containing 125,000 acres. It is a large and ambitious project whose several parts, as finally brought together, are adjusted to the attainment of that purpose. The parts were separately conceived, each having a purpose of its own. The project now is intended to draw on two independent sources of supply, each in a separate

watershed.1 The appropriations are necessarily distinct. Neither adds anything to, nor subtracts anything from, the status of the other. We are concerned with only one of them.

The proposed tunnel diversion from the Laramie was conceived as a possibility by Wallace A. Link in 1897 and was explained by him to Abraham I. Akin in the spring of 1902. Later in the year they visited the headwaters of the two streams, looked over the ground, and agreed that Link's idea was a good one, that the undertaking was large, and that they were without the means to carry it through. They concluded to promote the project together, and, thinking their chances of success would be improved by it, they also concluded to construct a ditch, known as the Upper Rawah, from the Laramie Valley to a connection with an existing ditch, called the Skyline, and to take water through these ditches into the Cache la Poudre Valley and there sell it. By this they hoped to demonstrate that water was obtainable from that source and to obtain money to be used in promoting their project. The Skyline was a fair-sized ditch leading over a low part of the divide to a branch of the Poudre, and they arranged with its owner for the carriage, on a percentage basis, of water from their ditch when constructed. They also conceived that the ditch could be used advantageously in collecting and carrying water to be sent through the tunnel if and when the tunnel diversion was effected. In 1902, beginning August 25, they surveyed the line of the Rawah, and in October of that year filed a statement of claim under it in the State engineer's office. In the statement they said nothing about a tunnel diversion and made claim only to the amount of water expected to be carried through the Rawah and to the use of certain lakes or natural reservoirs for storage purposes. No work was done on the ditch that year. In 1903 they cleared some of the land over which it was to run, but did no excavating. In 1904 they constructed 6,000 feet of the ditch and did more clearing. No work was done on it in 1905 or 1906. Further work was done in 1907, and some washouts were repaired in 1908. That was the last work on the Rawah. Much more than one-half of the ditch was left unconstructed. No water was delivered through it to the Skyline, nor was any sold or used. Nothing appears to have been done with the lakes or natural reservoirs.

În 1903 Link and Akin gave to each of three others a one-fifth share in their project, in return for which the new partners were to carry on solicitations to get capitalists interested and to raise money. The results of the solicitations were disappointing, but some investors were brought in and became concerned about the preliminary plans. Differences of opinion arose and had to be dealt with. The plans were examined and reexamined, alternative modes and places of diversion were considered and investigated, particular features were eliminated and others added, and in 1909, but not before, the project was definitely brought into its present form. A short reference to some of the details will serve to make this plain.

In the upper Rawah filing of October, 1902, nothing was said about the proposed tunnel diversion, but a claim was made to the use of certain lakes or natural reservoirs described as having an aggregate capacity of 325,000,000 cubic feet. The tunnel diversion was merely a mental conception until 1904. In March of that year a survey was made of a tunnel site, a ditch from the west fork of the Laramie to the east fork, and a channel reservoir on the east fork above the tunnel site; and in May following a statement of clain under them was filed, in which the estimated cost of the tunnel and ditch was given as $189,200 and that of the reservoir as $20,000. Later in 1904 a survey was made of a tunnel site, three collecting ditches, and two pipe lines, and in October of that year a statement of claim under them was filed, in which the estimated cost of the tunnel, ditches, and pipe lines was given as $375,000. The location and dimensions of the tunnel in the second survey differed from those in the first. The difference was not pronounced, and yet was a real change. In September, 1906, another statement of claim was filed covering the upper Rawah ditch, the lakes connected therewith, and the tunnel. This statement declared that the lakes were to be so enlarged that they would have an aggregate capacity of 1,250,000,000 cubic feet, instead of 325,000,000 as stated in the filing of 1902; and it again changed the location and dimensions of the tunnel-this time more than before.

In 1905 and 1906 surveys were made to find a route for an open canal from the Laramie around the mountains, through a portion of Wyoming and back to Colorado, which would avoid the construction of a tunnel and the maintenance of ditches in the higher mountain levels; and in 1908 a statement of claim covering such a canal

1 An engineer who had been connected with the work and was a witness for the defendants, said: "This system his two distinct and independent sources of supply; that from the Laramie River and that from the Poudre River Basin and the tributaries of the South Platte, and it was so designed that the Poudre Valley Canal could divert water from the Poudre River and also from the northern tributaries of the Poudre intercepted by the canal and from the tributaries of the South Platte as far east as Crow Creek and intercepted by the canal wherever there was surplus water. We estimated that the amount of water available outside of the Laramie River source would be between 80,000 and 100,000 acre-feet per annum as an average.

was filed, as was also a claim covering a large channel reservoir nine miles down the stream from the tunnel site. The estimated cost of the canal was given as $1,000,000 and that of the reservoir as $200,000. The plan evidenced by these filings was that of impounding the water in the reservoir and liberating it in an equalized flow into the canal, which was to carry it into the Poudre watershed without the aid of a tunnel. Late in 1908 and in the fore part of 1909 another survey along the same general line and with the same purpose was made at a cost of $15,000. Early in 1909 a statement of claim was filed covering a proposed reservoir near the tunnel site, the cost being estimated at $200,000.

In 1907 the Laramie-Poudre Reservoirs and Irrigation Co. succeeded to whatever rights the promoters had acquired up to that time, and all subsequent surveys, investigations, and filings were made by it. In April, 1909, the Greeley-Poudre irrigation district, within which the water is intended to be used, was organized. At that time sufficient capital had not been obtained to carry the project through in any form. In September following the irrigation company and the irrigation district the entered into a tentative contract, under which the company was to consummate the project in its present form, and, after doing the construction work, was to transfer the property to the district. Payment therefor was to be made in interest-bearing bonds of the district. By a vote taken the next month, the district ratified the contract and authorized the issue of the bonds. About the last of that month the work of boring the tunnel and making the diversion was begun.

It is manifest from this historical outline that the question of whether, and also how, this proposed appropriation should be made remained an open one until the contract with the irrigation district was made and ratified in 1909. Up to that time the whole subject was at large. There was no fixed or definite plan. It was all in an inceptive and formative stage-investigations being almost constantly in progress to determine its feasibility and whether changes and alternatives should be adopted rather than the primary conception. It had not reached a point where there was fixed and definite purpose to take it up and carry it through. An appropriation does not take priority by relation as of a time anterior to the existence of such a purpose. It no doubt is true that the original promoters intended all along to make a large appropriation from the Laramie by some means, provided the requisite capital could be obtained, but this is an altogether inadequate basis for applying the doctrine of

relation.

No separate appropriation was effected by what was done on the upper Rawah ditch. The purpose to use it in connection with the Skyline was not carried out, but abandoned. This, as Link testified, was its "principal" purpose. The purpose to make it an accessory of the large project was secondary and contingent. Therefore the work on it can not be taken as affecting or tolling back the priority of that project.

Actual work in making the tunnel diversion was begun as before shown, about the last of October, 1909. Thereafter it was prosecuted with much diligence and in 1911, when this suit was brought, it had been carried so nearly to a state of completion that, the assumption reasonably may be indulged that, but for the suit, the appropriation soon would have been perfected. We conclude that the appropriation should be accorded a priorty by relation as of the latter part of October, 1909, when the work was begun.

Applying a like rule to the Wyoming appropriations, several of them must be treated as relating to later dates, and therefore as being junior to that appropriation. Some of the projects in that State are founded on a plurality of appropriations, a part of which are senior and a part junior to that one.

The evidence shows that the Wyoming appropriations having priorities senior to the one in Colorado, and which are dependent on the available supply before named, cover 181,500 acres of land and that the amount of water appropriated and reasonably required for the irrigation of these lands is 272,500 acre-feet. A much larger amount is claimed, but our finding restricts the amount to what the evidence shows is reasonably required, which is one acre-foot per acre for the larger part of the lands, two acrefeet per acre for a part and two and one-half acre-feet per acre for the remainder.

As the available supply is 288,000 acre-feet and the amount covered by senior appropriations in Wyoming is 272,500 acre-feet, there remain 15,500 acre-feet which are subject to this junior appropriation in Colorado. The amount sought to be diverted and taken under it is much larger.

A decree will accordingly be entered enjoining the defendants from diverting or taking more than 15,500 acre-feet per year from the Laramie River by means of or through the so-called Laramie-Poudre project.

It is so ordered.

A true copy.

Test:

Clerk, Supreme Court, U. s.