There seems to be a fall of about 22 feet between A at the upper dam and B at the discharge from the troughs.[24] This fall in a distance of about 3,000 feet seems needlessly great; however, the primitive engineer has shown excellent judgment in the matter.  First, by putting the dam (upper dam) where it is, only half the stream had to be built across.  Second, there is a rapids immediately below the dam, and, had the Igorot built his dam below the rapids, a dam of the same height would have raised the water to a much lower level; this would have necessitated a canal probably 10 or 12 feet deep instead of three.  Third, the height of the water at the upper dam has enabled him to lay the log section of the waterway above the high-water mark of the river, thus, probably, insuring more or less permanence.  Had the dam been built much lower down the stream the troughs would have been near the surface of the river and been torn away annually by the freshets, or the people would be obliged each year to tear down and reconstruct that part of the canal.  As it now is it is probable that only the short dam will need to be rebuilt each year.

All dams and irrigating canals are built directly by or at the expense of the persons benefited by the water.  Water is never rented to persons with sementeras along an artificial waterway.  If a person refuses to bear his share of the labor of construction and maintenance his sementeras must lie idle for lack of water.

All sementera owners along a waterway, whether it is natural or artificial, meet and agree in regard to the division of the water.  If there is an abundance, all open and close their sluice gates when they please.  When there is not sufficient water for this, a division is made —­ usually each person takes all the water during a certain period of time.  This scheme is supposed to be the best, since the flow should be sufficient fully to flood the entire plat —­ a 100-gallon flow in two hours is considered much better than an equal flow in two days.

During the irrigating season, if there is lack of water, it becomes necessary for each sementera owner to guard his water rights against other persons on the same creek or canal.  If a man sleeps in his house during the period in which his sementeras are supposed to receive water, it is pretty certain that his supply will be stolen, and, since he was not on guard, he has no redress.  But should sleep chance to overtake him in his tiresome watch at the sementeras, and should some one turn off and steal his water, the thief will get clubbed if caught, and will forfeit his own share of water when his next period arrives.

The third method of irrigation —­ lifting the water by direct human power —­ is not much employed by the Igorot.  In the vicinity of Bontoc pueblo there are a few sementeras which were never in a position to be irrigated by running water.  They are called “pay-yo’ a kao-u’-chan,” and, when planted with rice in the dry season, need to be constantly tended by toilers who bring water to them in pots from the river, creeks, or canals.  On the Samoki side of the valley during a week or so of the driest weather in May, 1903, there were four “well sweeps,” each with a 5-gallon kerosene-oil can attached, operating nearly all day, pouring water from a canal into sementeras through 60 or 80 feet of small, wooden troughs.