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The Colorado at Austin drains some 40,000 square miles, and, of course, carries at times an enormous flow of water. The highest flood within the memory of the people now living was some 45 feet above low water, and from the best data I can obtain the flow of the stream was some 250,000 cubic feet per second. This would imply a depth of 16 feet on the crest of the dam, and the abutments should of course go to that height. At one end of the darn the natural rock goes far above that height. The other end is occupied by an artificial bulkhead, called the gatehouse, containing the sluices for drawing off the water. It is expected that the wash of the dam during floods will carry away the alluvial deposit for a considerable distance. The wheels, for this reason, must be some 200 or 300 yards from the dam, and the canal must have that length. As already stated, the formation permits this canal to be excavated in rock. At the entrance to the canal is the gate house alluded to above. Its function is to enable the water to be shut out of the canal in case of repairs and to prevent the canal from being overflowed in time of floods. The water will be drawn from the canal through iron pipes, pass the wheel, fall into the wheel pits and be discharged through underground races into the river.

WATER POWER.

It remains to consider the quantity of water power created by the proposed improvement. This consists of two elements, the fall, and the quantity of water available for power. The former is fixed approximately by the height of the dam. The latter can be inferred with more or less certainty from known facts. It is not the lowest stage that the river is ever known to attain to. It is the flow of water that can be depended on, with reasonable certainty, during ordinary seasons. Stages of the river above this minimum count for nothing unless steam is used to make up deficiencies.

The river is subject to great rises in times of heavy rains. On the cessation of the rains it falls rapidly until it attains a minimum flow, which appears to remain nearly constant. In that condition no water enters the stream from the surface of the ground. Its flow is wholly maintained by springs issuing from cavities in the rock, and is unaffected by current rainfall until the latter becomes sufficient to cause a flow from the ground. This is the present condition, and I conclude we shall not be far wrong in taking the present flow of the stream as the quantity that can be depended upon. This, as I have ascertained by careful measurement, is nearly 1,000 cubic feet per second.

There will, no doubt, be times during the hottest weather when the water will fall below this stage, on account of increased evaporation. I am told, however, that a month very rarely passes without rains in some part of the drainage basin, sufficient to cause a slight rise at Austin. The great extent of the pond will enable a considerable deficiency in the flow of the stream to be made good by storage. From the best information I can obtain, the pond will extend some 30 to 35 miles from the dam, with an average width of one-quarter of a mile, containing a water surface of some 8 square miles, and a total volume of something like 2,800,000,000 cubic feet of water. Should the flow of the stream diminish to one-half the above quantity, a single foot in depth on the pond will make good the deficiency for a period of five days, and 6 feet will make it good for thirty days.

A system of flashboards could readily be applied to hold the water 4 feet above the crest of the dam, and thus hold the surplus of water in store for such deficiencies, without drawing the pond below the crest of the dam. This feature will not become necessary for several years, and need not be considered further at present.

Owing to the imperfection of mechanism we can not hope to utilize, for practical purposes, more than 80 per cent of the absolute power of the water. Moreover, the full head of 60 feet can not be brought to act upon the wheels. Some part of the head will be consumed in the movement of the water through the sluices, canal, penstocks, and races. The head will at times be reduced by high water in the