IRRIGATION AND DRAINAGE INVESTIGATIONS. 35 



streams will irrigate can be extended by more skillful methods of 

 handling. So long as crop yields are not diminished, the greater 

 the economy in the use of water, the greater the value of streams, and 

 the greater the value of canals that distribute streams, but there is 

 a point where economy in the use of water cuts down the yield of 

 crops and then the increased value of the streams stops because 

 of lessened production and value of land. 



The work of this Office is to determine the methods by which the 

 ultimate limits of profitable economy can be reached. During the 

 past year the advanced work along this line has been of two classes : 

 (1) An attempt to determine the exact amount of water used by 

 plants in the processes of growth, and (2) an attempt to determine 

 what are the limits of profitable economy in the use of water in the 

 ordinary field practice where the necessities of plants and certain 

 inevitable losses from seepage and evaporation must be provided for. 



Work of the first class was carried on chiefly in California, and 

 that of the second class principally in Utah. The work in both Cali- 

 fornia and Utah was carried on in cooperation with the State and 

 the State experiment stations. In both cases arrangements were 

 made with irrigators in certain selected areas, who used water 

 according to schedules approved by the Office, or where the water 

 used was measured by the representatives of this Office. These ex- 

 periments promise to give very valuable data as to the water require- 

 ments of crops. 



These measurements, like those of former years, show that in many 

 cases half the water turned into canals is lost in transportation. 

 Earthen canals are not impervious. The bottoms of many leak like 

 a sieve. Water has now become so valuable and the injury from 

 seepage water so serious that some practical method of lessening the 

 leakage from canals will be of great value to irrigated agriculture. 

 In 1906 the Office cooperated with the State Experiment Station 

 of California in some comprehensive tests of canal linings whicli 

 included cement, crude oil, and clay. The Office carried on similar 

 experiments in Oregon with oil, lime, manure, and other substances. 

 The results of one year do not give sufficient information on which 

 to base definite recommendations, and these will be continued the 

 present season. 



Any method of practice which will lessen the water surface ex- 

 posed to the action of the air or restrict the time when a water-soaked 

 soil is exposed to the sun and wind will add to the area which a given 

 quantity of water will irrigate. Some of the experiments in Cali- 

 fornia were made to determine how much water could be saved 

 through applying the water below the surface or applying it in deep 

 and narrow channels where the wetted surface would be covered with 



