Regarding the alterations in sizes of outlets, whether or not there are alterations in their number and position, information as to the actual duties on the watercourses should be obtained. The discharge of the watercourses should be observed several times and added up and checked with the discharge of the distributary. The areas irrigated are known from the irrigation register. If the duties are abnormal the causes can be gone into, and a judgement can be formed as to how far they will remain in existence, and whether any watercourse is often kept closed. If so the outlet is too large. The duties, modified so far as may seem desirable, can be used for calculating the sizes of the remodelled outlets. But alterations of the sizes after a year or two years’ working will probably be necessary. The above procedure is also applicable to a case where the old watercourses had no masonry heads but were merely open cuts as on some inundation canals. A common case is that in which the channel is not remodelled--or at least its water level remains very much as before--but merely the outlets are altered in number, position or size, or in any or all of these. If the land irrigated by an outlet is high, the irrigation may be far short of what was expected, and the size of the outlet may have to be increased or its site shifted, generally upstream. This is often done at the request of the people, and at their expense.[36] [36] On some of the more modern canals the people are not allowed to pay for outlets, so that no question of ownership can arise. Old outlets should always be removed when superseded by others. Otherwise they are apt to be reopened or claims set up regarding them. Near the tail of a channel the discharge of an outlet may be an appreciable fraction of that of the channel. In such a case the adjustment of the size of the outlet, and that of the channel or of any weir or fall in the channel, should be considered together, the irrigation on the outlet and that on the channel downstream of it being compared. And similarly as to the sizes of any two or more tail outlets. Such outlets are sometimes left without masonry heads on the ground that this injures no one. It may injure an outlet upstream of them by drawing down the water. Tail outlets often need constructing or reducing in size to raise the water level in the reach upstream of them. 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.