Whenever the size of an old outlet is altered the design should be altered if unsuitable. The parapets should be brought into proper line, the roadway corrected, the floor level adjusted and any splayed wing walls abolished. If the outlet is skew it should be made square. All this should also be done to all old outlets or heads of minors even if the sizes are correct, whenever remodelling of outlets on any channel is undertaken.[37]
[37] Wherever an outlet is built or altered, a template, made to the exact size of barrel required, should be supplied to the subordinate in charge of the work.
It was stated in Chapter II. that the construction of masonry outlets on a distributary is not usually a final settlement of the matter. In many cases a proper proportion of water does not reach the tail. Even in such a case matters have occasionally been left alone, or the old and pernicious system of closing the upper outlets has been resorted to. In such circumstances the irrigation of a group of tail villages will be found to be less than that of a group higher up, the people to some extent acquiescing in the old idea that a tail village must be a sufferer. Government, or at least the Irrigation Department, has no particular direct interest in the matter. The total area irrigated, will probably be very much the same in any case. But an engineer who takes an interest in this part of his work will not allow matters to remain long in the state described. He will, of his own accord, adjust the outlets and equalise, as far as possible, the irrigated percentages. The people will disturb matters to some extent by enlarging watercourses, but there is a limit to this and it can be met by an occasional reduction of an outlet. A distributary, when once its outlets have been carefully adjusted, attains to something approaching perfection in its working. Any excess in the supply is taken partly by the upper outlets but part of it gets to the tail. Similarly any deficiency in the supply is distributed over the channel. The outlets which have a poor command and small head are most affected in either case. On the whole they do not lose or gain more than the others. The working of such a distributary causes great satisfaction to the engineer and not the least ingredient in this is the knowledge that he has wholly destroyed the power of his native subordinate.