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voir is over two and a half million acre-feet, and the solution of the mud problem that has been devised for that reservoir I consider applicable to the Colorado in the same way, and it is this: In the first place we build a reservoir of large capacity so that it will be perhaps a century, at least half a century before sufficient mud is collected in the reservoir to seriously impair its value as a storage reservoir—that is, it has a surplus capacity built in advance. It is possible to build that dam higher, and that may be what will be done at that time. But the time will come, if the project is continued, when the accumulated sediment in that reservoir will reduce its capacity below the point that is necessary for the service of the lands below. That will mean in that case that there will be a long reservoir, 45 miles long, and most of the sediment will be deposited at the upper end, a large part of it, and a great deal of it above the water line, because when a river is in flood it backs up on account of the obstruction of the dam, and a very large capacity will be filled above the flow line of the reservoir. Mr. LITTLE. Do I understand you to say that the mud, most of it, starts way above the dam? Mr. DAVIS. All of it starts above the dam; yes, sir. The CHAIRMAN. Where the water overflows—backs up? Mr. LITTLE. Of course, it goes slowest when it gets to the dam, and isn't more mud deposited around the dam? Mr. DAVIs. No; the large quantity is deposited all the way up and down there back of the dam. Mr. TAYLOR. The water backs up there 5 or 6 miles where it is perfectly still, and the mud commences to drop as soon as it strikes that still water. Mr. LITTLE. I had a lawsuit about it one time, and I found that most of the mud was deposited around the dam, according to the witnesses. Mr. DAVIS. It has been our experience that where a stream carries sediment it begins to deposit it some distance above the dam. I can show you on the Pecos River, and on the Salt River, and at various other places, where there are large deposits of sediment at a higher elevation than the spillway of a dam where the water runs over, as much as 11 feet, which means that the water has been 11 feet over the top of that spillway. The water at the head of the reservoir was a little higher, enough to make it run. The CHAIRMAN. Isn't one explanation that there is much more sediment being carried; that the farther up you go, the more sediment is being carried, and that is being reduced all the time—the percentage to draw from ? Mr. DAVIs. Whenever turbid, running water is checked it begins to deposit sediment. Mr. LITTLE. How do you account for the fact that in a lawsuit that I had, which went to the Supreme Court—in fact, I have had five or six of them, and all the witnesses testified that there was more mud down at the dam than there was anywhere else? Mr. DAVIs, I don't know what the circumstances were. That might have been true in that case. Mr. TAYLOR. Was that Kansas mud! Mr. LITTLE. It was just a mill dam in Kansas, a couple of them. Mr. DAVIS. The time will come, of course, when the accumulated sediment in the reservoir, in spite of devices that will be used to discharge part of the sediment—several devices to postpone the day have been devised, and I think will be carried out, but when the time does come, when the reservoir does not accomplish its purpose by reason of lack of capacity, it will exhibit that by running dry when it is needed. Whenever the reservoir runs empty the stream will cut down through the thread of the reservoir, a distance in that case of 45 miles, and carry out that mud were it runs out of the opening through the dam. It will carry out a large amount of mud whenever it is in that stage; that is, there will be no pond in the reservoir when the water is runnig through, and when that happens, when that time comes, we will build another reservoir, a smaller one, on the headwaters, where the stream is clearer, and then in handling those two reservoirs in conjunction we will always draw on the lower one whenever there is water in it. We will draw on that until it is empty, and then turn water out from above, and as the water runs through it will wash out a great big channel there. The accumulated mud contributes a large amount of seepage all the time. It is thoroughly watersoaked and there is a great mass of swamp land, seepage land, and whenever the water goes down below the level it cuts a channel through. Freshly deposited mud cuts very easily and rapidly by running water, and whenever the reservoir is empty and water is being drawn from the natural flow of the river or from the reservoir above, it will cut out the sediment. Now, if that reservoir being handled in connection with the main reservoir is not sufficient, another can be built. There are small reservoir sites on the headwaters of the Rio Grande, as there are on the headwaters of the Colorado. The time is long in the future when they will have to be built, but they can be built at less cost than the lower ones, and serve in that way and eventually we will get a system of operation and a quantity of storage capacity which will maintain its equilibrium by cutting out the sediment as rapidly, on an average, as it is brought in by the flow of the stream. Mr. SMITH of Idaho. If you have reservoir sites your plan is all right, but if you do not have reservoir sites up the river then the reservoir eventually becomes useless. Mr. DAVIs. Yes, sir; we must have reservoir sites on the upper river in order to make that possible. That would be comparatively clear water. The CHAIRMAN. It may be a century or half a century before they will need that reservoir. Mr. DAVIs. Yes, sir. Mr. LITTLE. How do they avoid the collecting of so much mud from the dams on the Nile so that they become useless? Mr. DAVIs. In the Assuan dam on the Nile it is handled in this way: There are 187 large openings—gates—in the dam, and whenever the river is in flood they open all those gates. When the river is in flood it carries most of the sediment and they let all that flood water run to the ocean and while that is running through it is carrying its heavy load of sediment and it also cuts out previously deposited sediment. Then when the river is on a decline and is not carrying so much mud they close the gates and they still have enough water with which to irrigate.

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The CHAIRMAN. Is that sediment still used along the Nile to fertilize the lands? Mr. DAVIs. Yes, sir. Mr. LITTLE. Is that the system used at the other dams on the Nile? Mr. DAVIs. The other dams are simply low diversion dams that do not store any water. They are filled all the time; simply a channel through them. In the case of a diversion dam it does not matter if it does fill up. Laguna dam filled up with sediment the first year. Mr. LITTLE. Now, I don't know what you mean by that. If they are filled up with sediment, of what use are they? o, Mr. DAvis. It simply diverts the river; it doesn’t store any water; that is the case with the Laguna Dam. Mr. LITTLE. There is one on the Nile below Cairo that has been there for 70 or 80 years, and part of the year it is closed up, and there must necessarily form some body of water there. o Mr. DAVIS. It is filled with sediment, though. The CHAIRMAN. Now, Director Davis, you deem that the provisions of this bill will give them a more comprehensive report than anything that has yet been made in regard to surveys of the valley as one proposition; that is, taking it altogether, the other surveys—the information that you have gained from the other surveys has all been combined? . . . Mr. DAVIs. Yes, sir; the information existing has been well combined in the last report issued by this board, of which you have a copy. I wanted to make another statement, Mr. Chairman, of the work that is necessary. Next to the investigation of storage, which is vital, in my opinion next in importance is an investigation of the soil. The Imperial-Laguna Mesa is a very large tract of practically unknown land, very sandy and difficult to travel over in an automobile, not because there is any brush in the way, because there isn't, but on account of the sand. The physical appearance is similar to the Yuma mesa and its formation is probably somewhat similar. We have examined the Yuma mesa fairly well, and we believe that to be good soil, although it greatly needs humus. But that is the only line that we have on the value of the Imperial-Laguna mesa. There should be a thorough investigation made of the physical and chemical characteristics of that soil before a vast amount of money is spent in irrigating it. It may be that some parts will have to be eliminated. Another thing that ought to be investigated is the areas that can be irrigated feasibly by this canal system. Those areas have not been classified into o and nonirrigable lands, and that should be done, so that we will know how large to build the canal and how much land we will have to draw on and the character of the land. Now, this soil survey is necessary for an intelligent classification of the irrigability of that land, how much of it is irrigable, and what class it belongs to, and whether it is first class or second class; and there are questions as to whether the various districts, Coachella district, will come in and cooperate, and so on. The CHAIRMAN. You want to apportion off, though, the contribution that each agency will make if it does participate? Mr. DAvis. Yes, sir; this bill requires that, and that, of course, is one of the questions inseparably linked up with the one of who will cooperate. That depends largely on what terms they can obtain. If they have to take a secondary water supply they will pay so much and if they take a first water supply they will pay so much. Mr. TAYLOR. In that connection, the thought has been running. through my mind here as to whether or not it would be advisable or whether we ought to embody in this bill something about the Secretary of State—ask him to join in negotiations with the Mexican Government about that condition down there, or is this entirely our own affair on our side of the border without any consideration of the people below us? Mr. DAVIS. Of course it is impossible to eliminate the Mexican menace from this problem without some action. I don't believe that. there is any necessity at the present time of covering that in the bill. . Mr. TAYLOR. It seems to me that it would be a good idea to make some definite arrangement, if we can have it, with the Mexican: Government, that would be enforceable, and something that is: tangible, so that we will know where we are at on this thing, so that, we will not be shooting all the time in the dark, so far as Mexico is concerned. Mr. SUMMERs. Let me call attention to section 2, which says that the secretary shall make a report to Congress not later than the 6th day of December, 1920, as to the result of his examination, together with his recommendation as to the feasibility, necessity, and advisability of the undertaking of the participation by the United States in a plan of irrigation development with a view of placing under irrigation the remaining unirrigated public and privately owned lands in that valley. Under that it seems to me that one secretary will have authority and will be supposed to call on the other where there was an international question involved. Mr. HAYDEN. Mr. Davis, you spoke a moment ago about provision, which begins on line 25, page 2: “The proportion of the total cost that should be borne by the various irrigation districts, or associations, or other public or private agencies now organized, or which may be organized; and the manner in which their contributions should be made.” Is it your understanding that that would require the Secretary of the Interior in making this report to definitely determine exactly the contribution that should be made by each organization, or would the secretary make only an approximate estimate? Mr. DAVIs. I should think it would be merely a recommendation on his part, and that it would be subject to modification afterwards. Mr. HAYDEN. It appears to me, the way it reads, to be a very rigid direction. The bill says that the said Secretary shall also report the proportion of the total cost that shall be borne by the various irrigation districts now organized or which may be organized, and the manner in which their contributions shall be made. If he made a finding to that effect, it certainly should be subject to review. It seems to me that the bill should read “the approximate amount,” so that there would be a little leeway. The CHAIRMAN. It says “in his opinion.” That is a mere recommendation. Mr. DAVIs. Yes; that is what I understand it to be. Mr. HAYDEN. My idea is that it would be better to say “approximate proportion.”

The CHAIRMAN. That is all it could be, anyhow, an approximation. Mr. Davis. I suggest, Mr. Chairman, that in line 16, page 3, the words " at least” be inserted between “of” and “one-half," so that it will read: “ Provision shall have been made for the payment of at least one-half the cost of the examination."

The CHAIRMAN. I think that is a good suggestion. It occurred to me when we were speaking of that before.

Mr. SUMMERS. Then you will have to modify that “one-half” to 6 not to exceed one-half” in the eleventh line of the same page,

Mr. HAYDEN. Make it “not to exceed one-half.”

Mr. SUMMERS. That would make it specific as to the gross amount.

Mr. HAYDEN. There is one other question I wanted to ask Mr. Davis about the bill. On lines 3 and 4, page 2, it reads lands " which can be irrigated at a reasonable cost from known sources of water supply.” Is there any other known source of water supply than the Colorado River and will not all the water be diverted at the Laguna Dam?

Mr. Davis. It would; there is possibly some well water that might be pumped. I don't know why that was so expressed.

Mr. HAYDEN. The idea I have is this: That the people of the Imperial Valley have in mind a definite proposition; that is, they want to connect their present irrigation system with the Laguna Dam; they want to get water from the Colorado River from no other source. It seemed to me it would be easier to explain the bill to all concerned if instead of saying “known sources of water supply ” we would say, " which can be irrigated at reasonable cost from the Colorado River by diversion of water at Laguna Dam.” Mr. Davis. I think that would be better. Mr. SUMMERS. What line is that? Mr. HAYDEN. Lines 3 and 4, page 2. Mr. BARBOUR. Might not that have the effect, Mr. Hayden, of restricting operations?

Mr. HAYDEN. If there was any other known source of water supply, I would say yes, but there is not.

Mr. BARBOUR. Then, if there is not, why change it?

Mr. HAYDEN. It is better always to state the concrete facts, if possible. Now, if there is, in Mr. Davis's opinion, any other known source of water supply, it might be necessary to use the broader terms, but since he has expressed the opinion that all that anybody intends to do is to connect the present irrigation system in Imperial Valley with the Laguna Dam, why not say so?

Mr. Davis. I don't see any objection to your suggestion. One thing that might occur to some is that water is carried to Volcano Lake, for example, from Colorado River, and then is carried from there into Imperial Valley.

Mr. HAYDEN. That would require the construction of canals in Mexico, which nobody intends to do.

Mr. Davis. Yes, sir. Mr. SUMMERS. Doesn't this contemplate the headwaters of the Colorado, the Grand, or something of that kind? Isn't that what it indirectly refers to ?

Mr. Davis. The storage might be up there but it does not contemplate any irrigation except the Imperial Valley.

Mr. BAYDEN. L: What line would be

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