sons. As noted above, they can probably be filled once even in the driest years. The combined capacity of the reservoirs is 41,367 acrefeet. By this estimate it is seen that it will be possible to start at the beginning of the dry season with full reservoirs, which, with the duty of water at 2 acre-feet, will provide irrigation for about 20,000 acres in very dry seasons. This is sufficient to carry through a dry year such crops as alfalfa, as well as orchards, etc. In seasons of ordinary rainfall the reservoirs should provide water for irrigating 40,000 acres, and in wet seasons 60,000 acres or more. It is believed that this estimate is conservative.

The reservoirs are thus seen to serve as regulators of the flood discharge as well as storage reservoirs.

To carry this water to the lands below it will be necessary to construct a canal approximately as located on Pl. II. This canal can be so located as to divert flood water from Salinas River between Kings City and Soledad, and the canals from the San Lorenzo and Arroyo Seco could discharge into it during the latter part of the season, supplementing the winter flow, if necessary. It is believed that such a canal, in connection with the reservoirs, will supply water to all the best irrigable land from Soledad to the Bay of Monterey. No surveys for such a canal and no estimates of its cost have been made by the United States Geological Survey.

The stream carries but a small percentage of silt, and the water is very pure, in every way suited for irrigation and domestic use.

The following table of analysis shows the character of this water at the gaging station the first of the season after a slight rise:

Other analyses show that the flood water contains slightly less mineral matter.

EXTENSION OF IRRIGATION BY PUMPING WATER.

If the above-described reservoirs and canals are constructed it is probable that pumping water for irrigation will decrease rather than increase in the lower Salinas Valley. The high price of fuel makes pumping expensive and in the future it will undoubtedly be limited to procuring water for domestic supplies and for the irrigation of small garden patches. The underground water conditions of the

a Calculated as compounds. U. S. Department of Agriculture, Bureau of Soils. Bailey E. Brown, analyst.

lower Salinas Valley have been described on page 21. In the upper Salinas Valley and the mesa regions it is not improbable that sufficient water for stock-raising purposes could be reached by deep wells. Deep-well pumps driven by powerful windmills would raise the water to the surface and make available range lands now unused. For a detailed description of pumps and windmills used for such purposes the reader is referred to Water-Supply and Irrigation Papers Nos. 1, 8, 14, 29, 41, and 42 of the United States Geological Survey, and for a description of the methods of irrigation from wells to Water-Supply and Irrigation Paper No. 20.

SUMMARY.

The important results of the hydrographic investigations are summarized in the following table:

In the above estimate interest was calculated at 6 per cent and taxes at 0.8 of 1 per cent on the total cost of the dams and reservoirs. In each case an additional charge of $3,500 per annum was made for maintenance and supervision.

The last column of the foregoing table gives the cost per acre-foot per annum of water stored at the above-mentioned reservoirs. Data are not available to estimate the loss by seepage in canals and by evaporation, but in estimating the amount of land that can be irrigated a liberal allowance has been made of the duty of water. It is assumed that for each 1.5 acre-feet of water put on the land 0.5 of an acre-foot will be lost in the canals. About 1.5 acre-feet per annum is the average amount of water actually used on the land. The Leigh reservoir and Pinkerton reservoir are not of special value at present, but may be valuable adjuncts to the water supply of the Salinas Valley in the future.