THE RAISIN INDUSTRY. 81 



ditches should run out at right angles if possible, or if the ground 

 is very uneven they may follow the highest parts. The ground 

 between these ditches should be properly leveled into checks. 

 With checks the irrigator simply measures a piece of ground of 

 any size which is surrounded by a levee or bank. This bank must 

 be high enough to allow the water to cover all of the ground as soon 

 as the check is filled with water from the ditch. 



To make the ground level enough, it is generally necessary to 

 level it with scrapers. The more level is the surface the better, 

 cheaper and quicker will be the irrigation, and no small amount of 

 trouble will be avoided if this work is properly done before the vines 

 are planted. Too little of this leveling is done in some places, and I 

 have seen thousands of acres planted in Muscat vines which were so 

 improperly leveled that the profits of the vineyard in after years would 

 be seriously interfered with. To understand how this can be possible, 

 we must remember what takes place when we irrigate and after we 

 have irrigated. The gate in the ditch is opened, the water flows out 

 and runs immediately down to the lowest part of the check. When 

 this part is reached, the check begins to fill up. If the ground is 

 very uneven, it may take days to fill the check, and the lower part 

 will require to be covered several feet with water before it will reach 

 the higher parts, which always need irrigation the most. To back it 

 up so high requires also a correspondingly high levee, which again is 

 more apt to break and cause trouble and expense the higher it is. After 

 the water has reached the highest possible point, the flow is shut off, 

 and the water begins to subside. The highest part of the land becomes 

 dry the first, and quickly, while it may take days or even weeks to dry 

 up the lowest part of the check. When at last the check is all dry it 

 may be found that the lowest vines have been injured or entirely 

 drowned out. When summer irrigation is used, it is absolutely neces- 

 sary to have the ground level, so that when it is flooded the water will 

 not reach up to the grapes, as they spoil when coming in contact with 

 the water. 



The time when flooding should be. used must depend upon circum- 

 stances. As a rule, flooding is especially adapted to winter irrigation, 

 as, when the vines are entirely dormant, they may be submerged for 

 months without suffering any harm. Young vineyards may also be 

 flooded in summer time, but, when the grapes begin to appear, flooding 

 can only be done in the winter or when the land is absolutely level, 

 but even under the most favorable circumstances many grapes are 

 always lost. Some have so prepared their vineyards that a check, 

 when flooded, can be drained into a lower check or into a ditch. This 

 is a very good arrangement where the land is not entirely level, as it 

 will cause the low places to dry up as quickly as possible. But a 

 better way is to have the ground so level that the water will sink 

 evenly and leave no sinks nor any high and prematurely dry places. 

 There are, however, soils so composed that the water cannot sink 

 through them in any reasonably short time. Such heavy soils must be 

 surface drained after every flooding, or perhaps had best be given up 

 to some other method of irrigation. But such hard or impervious 



