When the discharge of the canal exceeds 3,500 c. ft. per second there is, when B and C are receiving water, a second residuum, which goes to A. Tables can be worked out for several discharges of the main canal, but it is the minimum discharge which is the most important factor in the case. The minimum discharge, or something very near it, generally lasts through about half the crop, and it is when the supply is at a minimum that care and justice in the distribution are most needed. The chief objection to the arrangements above described is that the surplus to be sent down one channel or another is sometimes so small that it must be to a great extent wasted. The best means of preventing this is to have the discharge tables, including one for the main canal at some point higher up than the trifurcation, constantly corrected. In that case, it is known under what circumstances a small surplus will occur, and the orders can be modified so as to prevent its occurrence. The orders will of course be more complicated, and will have to be dealt with by an engineer and not a gauge reader. The turns, once satisfactorily arranged, may go on for years without alteration. They may require altering if any branch is found, in the course of time, to be doing worse than or better than the others, though the correction can probably be made by altering the full supply gauge. The turns of the branches having been arranged, it remains to settle those of the distributaries. The total available discharge being, as before, assumed to be rather more than one-third of the full supply discharge, each distributary taking off from the main canal, where it is not possible or not desirable to regulate the height of the water level in the canal, can be run with full supply for four or five days out of each fortnight, and then closed. Whether it be four days or five may often depend on special circumstances such as whether the distributary is doing well or otherwise. If necessary the full supply can be adjusted. When the canal supply increases the four or five days can be increased.