436 



REPORT OF OFFICE OF EXPERIMENT STATIONS. 



and the lateml ditches discliargc directly into the reservoirs. In addi- 

 tion to the laterals, shallow shovel ditches, corresponding to the old 

 "quarter drains," are maintained at right angles to the furrows, and 

 thus collect the water rapidly from the fields and discharge it into 

 the ditch system. These latter are made new each year and they 

 vary in arrangement and size to meet the individual re(|uirements. 



Although subject to variation, the main reservoir canals range in 

 width from 30 to 60 feet and usually have a depth of from 5 to 8 

 feet. The deeper the canal the greater storage capacity it possesses 

 and the better outlet it furnishes for the collecting ditches or laterals, 

 as the case may be, and it is also less liable to water-growth obstruc- 

 tions. As shown in the following table, the reservoirs of the three 

 plantations under investigation have varying capacities, equivalent 

 to a rainfall on the tributary lands of from 0.1 inch to 0.4 inch. 

 It would seem preferable to construct reservoirs having even greater 

 capacity than the larger amount mentioned, as, by so doing, the 

 size of the pumping plant can be decreased. This table from Mr. 

 Shaw's report, besides showing the reservoir capacity, also gives the 

 length of the various ditches and area occupied by them and gives, 

 as well, the normal capacity of the pumping plant in inches of water 

 depth per twenty-four hours. It will be noticed that the ditch 

 systems of these three plantations only occupy from 3 to 6 per cent of 

 the area, which is a decided decrease from the 10 and 20 per cent 

 under the old ditching system, as previously mentioned. 



Data of ditch systems. 



The arrangement of the collecting ditches largely depends upon the 

 shape of the fields and the natural topography of the land, and also 

 upon the method and kind of cultivation that is desired. The endeavor 

 is to arrange them, however, so that they may get the water from the 

 fields into the reservoir canals as promptly as possible. They vary 

 from 4 to 10 feet in width and are usually maintained at a depth of 

 from 4 to 5 feet. 



