THE IBRIQATION AOE. 



299 



an inch (rain measure, remember), or less on the side 

 opposite place of delivery. You may think you can fix 

 this by having the bottom of the check on a slope with 

 water delivered at the highest edge so that it will run 

 over quickly. The theory of the novice is that while it 

 is running over the high ground it will be soaking in 

 while the water that collects on the lower ground will 

 compensate in the time it stands and soaks in for the 

 greater length of time that it was running over and 

 soaking into the higher ground. This would be very 

 fine if the soil were all of uniform texture, perfectly 

 graded and perfectly bare, the first two being conditions 

 you are not apt to get. But when it is covered with 

 vegetation you can be certain that uneven wetting will 

 result. And this cannot be prevented by any number 

 of delivery gates at the upper side. Good gates cost 

 money and labor and one to a check is generally all you 

 can afford, for it is enough if other conditions are right. 

 And the first of these conditions is a head of water pro- 

 portionate to the size of the check. 



Mark now the distinction between the quantity of 

 water you have, measured as a running stream, and the 



A private reservoir to do this would cost too much in 

 most cases, but every well managed ditch is practically 

 such a reservoir. Instead of each consumer taking 

 water continuously he takes a larger amount at inter- 

 vals of many days. This enables every consumer to get 

 the amount he wants with almost a certainty, provided 

 he puts in his order to the ditch-tender or secretary 

 long enough ahead to allow him to arrange matters so 

 that he does not interfere with other consumers. The 

 amount thus taken is called "an irrigating head," while 

 the amount for the year which it equals in continuous 

 flow is called the "water right." Using a big "head" 

 once in a while, instead of a continuous flow, makes 

 lively work for a short time and puts the water into 

 the soil with the smallest amount of waste from con- 

 tinued soaking after it has enough. The constant flow 

 keeps work going all the time to irrigate a much smaller 

 area. Consequently, the larger the head the more work 

 it will do provided it does not cut out gates or levees 

 or wash 'too much mud and silt where it is not wanted 

 or interfere with proper clearance of the checks after 

 enough water has soaked in. 



Headgate Tri-State Canal, near Scottsbluff, Nebraska. 



amount you can have available for use at a given time, 

 for there is nothing more important. Suppose your 

 water right is a second foot to 160 acres, a usual al- 

 lowance for common farming in many sections. This 

 is on the assumption of a continuous flow of that 

 amount, and if from a private artesian well, small 

 running stream or pumping plant, it will probably be 

 such a flow. But a continuous flow is the last thing 

 you want for that amount of land. What you need will 

 be the equivalent of such a continuous flow instead of 

 the actual flow. A second foot running all the tune 

 would be such a slow feed into checks of reasonable 

 size that half or two-thirds of the water might be wasted 

 by too much soaking into the upper part of the checks 

 before reaching the lower parts. It would also take much 

 more time and labor to watch it and change from check 

 to check than if you had, say, ten times that amount 

 running for one-tenth of the time. In fact, for some 

 results a second foot every day for 365 days may not 

 be as good as 365 second feet for one day. 



Therefore, you need some kind of a reservoir to 

 accumulate the flow five, ten, twenty or forty days or 

 more, according to your climate, soil and crop and give 

 you the whole accumulation in a much shorter time. 



This result cannot always be reached by making 

 the checks small enough. You may find every gate 

 needs a cross gate in the ditch which will increase the 

 cost. You may have to drive haying machinery over the 

 levees and must not have them too numerous. There 

 is a temptation to make them flimsy to save the in- 

 creased cost of so many more and if well made there is 

 so much more room for gophers and such things to 

 climb up in to escape drowning. 



On the other hand, the larger the checks the more 

 difficult it is to adapt the size of the head so as to 

 prevent waste of water from too much soaking on the 

 entrance side more -dangerous from waves washing out 

 a levee when full of water, more damage if it does 

 break, and more difficulty in having quick clearance of 

 the water where soil or climate makes it necessary. 



Near Lerdo, Mexico, in 1884, I saw a check of 

 about one thousand acres, all in corn. It was an old 

 lake bed apparently dead level and took about all the 

 flow of the Nases Kiver over a day to fill it. The corn 

 was very fine, but I think it was due to excessive rich- 

 ness of the soil rather than good irrigation. I could 

 see no reason for making so large a check except the 

 saving of labor in the first instance to pay for it later 



