In the case above described the channels flowed for only five months in the year. Some of them silted a good deal but as this silting was roughly the same every year, it did not greatly affect the question of outlet sizes. On a perennial distributary of which the head reach silts during part of the year and scours during the other part, a proper distribution of supply by adjustment of outlet sizes alone may be more difficult. If the silt was frequently cleared, this would cause needless expense and interference with irrigation. In cases where the distributary is not run constantly, something can be done by attending to the regulation. When there is silt in the head reach, the discharge can be reduced and the period of flow proportionately increased. The lowered water level reduces the supplies of the upper outlets, and increases the discharges of those lower down. Moreover the periodical silting and scour are not always serious. Also it is not essential that the supply to each watercourse should be exactly the same every year. There are always good and bad seasons. It is sufficient if a watercourse is not allowed to suffer on the whole, and is never allowed to suffer much. There is no doubt that it is possible to deal satisfactorily in the above manner with very many distributaries. It is frequently reported that “difficulty is experienced in getting water to the tail.” This is owing to timidity in reducing the sizes of outlets. The suitable plan is to reduce them to such an extent as to cause a proper supply to reach the tail and then, if necessary to enlarge some. It has been already remarked that only a short length of the barrel need be altered. The cost of this is very small. The real difficulty in the case is not the impossibility of securing good results, but the impracticability, in many cases, of securing the constant attention which the procedure demands.[38] [38] See also Chapter V. Art 3. 8. =Miscellaneous Items.= At the headworks of a canal there is a permanent staff of men who work the gates and look after the works. They assist in discharge observations and in reading the gauges, and they may have to take soundings in the river to see what changes are taking place. Some one is on watch day and night and reads the gauges at frequent intervals. The officer in charge occasionally inspects the works at night without notice. Detailed rules regarding the above matters, and any others that are necessary owing to special local conditions, are drawn up. Sometimes there is difficulty in getting the staff to attend properly to the regulation of the supply in the canal at night. Probably some “tell-tale” watches would be useful. They would at least show the times at which the men concerned went to the gauges or other points. At the headworks, and at all important regulators, a stock of concrete blocks should be kept ready for the execution of any urgent repairs.