13 



cane fields,has seriously stunted the growth. Now in studying the table 

 we find that practically each year has a month during the growing season 

 in which the moisture is deficient, although there are only two seasons, 

 i. e., from July to October, 1912, and from October 1906 to January 

 1907, in which the drought was almost as serious as this year's. The 

 table furthermore shows that, in addition to the rainfall, the land 

 requires an average of 25 inches of moisture, to produce the best results, 

 the maximum being about 30 inches, and the minimum about 15 inches. 

 This compares favorably with the cane fields along the south side of 

 the island, where the irrigation requirements are from 30 to 60 inches, 

 and where the irrigation is of vital importance. Due to this fact, 

 you must not expect to pay as much for irrigation as the people 

 on the south side. 



Although it is assumed that the land requires an addition of 25 

 inches of moisture during an average year, the amount to be provided 

 by irrigation must be greater, thidiiue to the losses in the canal and 

 laterals and in the fields themselvs. These losses in a new system 

 before the canals and laterals are primed, are rarely less than 50%, 

 and in an old and well built system are rarely under 20%. 



It is now assumed that this region (Fajardo) needs irrigation, 

 although intermittent, and that the sources of supply are next to be 

 discussed. The first and generally the cheapest source of supply is a 

 perennial stream, and after the natural flow of this is developed, a 

 reservoir to hold back the flow for use in the periods of drought, can 

 generally be built cheaper that a pumping plant, deriving its supply 

 from wells driven into the underground reservoir, giving due consi- 

 deration to operating and maintenance charges, 



At present you have a large and undeveloped flow in the Fajardo, 

 Mameyes, Blanco and the small streams of this vicinity, which can be 

 utilized for irrigation very cheaply, but it is apparent that there is 

 more land to be irrigated during the periods of drought than can be 

 supplied by the natural flow of these streams, and that sooner or later 

 additional development will be desired. Now surveys of land can 

 always be made in a short space of time, but due to the ever-varying 

 flow of a river from day to day, from month to month from season 

 to season and from year to year, it is necessary to have a consecutive 

 record of the height and discharge of a stream extending over several 

 years before any plans can be drawn for the complete utilization of 

 the water furnished by these streams. For a pai-tial development such 

 as you are making now, such a record is not very important, but the 

 time will come when it will be desired to irrigate additional lands that 

 such a record will be very valuable. 



Yesterday morning (August 14th) the Fajardo River was dischar- 

 ging 1,250 liters per second, or about 29 million gallons per day, but 

 at that time it was not at its lowest stage, and since no record is 

 available, low flow of more than 550 liters per second cannot be as- 

 sumed with safety for a period of drought. This would irrigate 

 approximately 1,500 acres, provided irrigation was carried on through 

 out the 24 hours of the day, and leave an ample margin for losses- 

 in the irrigation system of evaporation and seepage. In addition to 

 this land irrigated by the Fajardo River, a large area can also 

 be irrigated by the other streams of this vicinity. 



In order to irrigate land by gravity, the following structures are 

 generally needed: 



