3 66 THE POPULAR SCIENCE MONTHLY. 



In the former nothing is done except to dig a large ditch 

 through the field, as near the middle as is consistent with its fol- 

 lowing sufficiently high ground, or between two fields, if both are 

 to be watered from it. Through this ditch, or zanje, a slow 

 stream of water is kept running. It soaks into the ground and 

 percolates or " seeps " through it and thus sub-irrigates the whole 

 field without any lateral ditches. Of course, this occurs only in 

 peculiar soils. Its best exemplification is in Fresno and Tulare 

 Counties, California. Sometimes a single ditch, nearly straight, 

 will in this way irrigate one hundred and sixty acres. 



The other method is exactly opposite. The whole field is 

 flooded. Head-gates are placed along the main ditch, and from 

 every head-gate a dike or levee is run across the field. Levees 

 are also run along the sides, one of them forming the outside of 

 the ditch. If these levees ran at right angles, a field thus pre- 

 pared for irrigation would look for all the world like a huge 

 printer's case. The levees may be two to four feet high. The 

 intervening spaces are called " checks," and may contain any 

 amount of land. I have seen one thousand acres cut into checks 

 of from one to ten or twenty acres. I did not see how it could 

 pay. Nothing was grown but hay and pasturage. 



The checks are leveled, if not already sufficiently level. They 

 are flooded one at a time. In flooding check No. 1, head-gate No. 

 1 is opened and No. 2 closed. As soon as the whole surface of 

 this check has been covered with water, head-gate No. 2 is 

 opened, and the same flood runs back into the ditch and down 

 into check No. 2, and so on. The water is kept on the land but a 

 short time. In warm weather the flooding is done mostly at night. 

 The basins or checks formed by the dikes are not filled with 

 water. 



Alfalfa hay is cut four or five times a year, and the land is 

 flooded after each cutting. Twelve tons a year per acre are not 

 a rare crop, though less is commoner than more. For wheat and 

 other cereals one good flooding is enough. 



A good deal of California land has been over-irrigated. Al- 

 kali has been brought on or brought up, the soil has been made 

 heavy, pools have been formed from the " seepage," and orchards 

 and vineyards have been spoiled. After a field has been irrigated 

 for a few years it becomes saturated, and wells dug in it soon 

 reach water. It no longer needs so much water, and its former 

 supply may be carried on to reclaim new deserts. How much a 

 single river will reclaim, only give it time enough, can be vaguely 

 guessed. Thousands of acres in the San Joaquin Valley have 

 been placed beyond the need of further irrigation. The whole 

 valley was once a desert. 



A part of it seems beyond the reach of any irrigation except 



