IRRIGATION IN FIELD AND GARDEN. 



BY PROFESSOR E. J. WICKSON. 



(Reprinted from Farmer,,' Bulletin No. 133, issued by U.S. Dopt. of Agriculture. 

 DEVELOPMENT OF WATER IN DRY STREAM BEDS. 



Development of water in dry stream beds is a frequent recourse 

 where the bed is largely composed of sand, gravel, or rock debris of 

 various kinds. In the arid region especially the visible stream is 

 often only a fraction of the water moving along a stream bed, and 

 when no water is in sight there is frequently considerable underflow 

 during the dry season. On large streams water enough has been in- 

 tercepted to supply large irrigation enterprises, and in many cages a 

 small stream will yield a valuable farm supply. 



The first thing is to determine by a prospect in the dry season 

 whether an underflow exists when the surface flow has ceased. Select 

 a point in the stream bed where it seems to be confined to a deep, nar- 

 row channel, as well as can be judged by the steep, rocky banks, and 

 excavate a hole or well down to water and open out the bottom so as 

 to obtain a water surface like that in a well. By observing this it can 

 be determined whether a water pocket or an underground stream has 

 been struck. In case of a stream the movement can be detected by the 

 collection of light litter, etc., on the downstream side, or, in case of 

 a considerable movement, the flow of the water can be detected by the 

 action of the lighter sediment. If no movement can be detected, the 

 effect of pumping from the hole will give an idea of the amount of 

 water available by the length of time the hole will stand pumping. 



Supposing the prospect is promising by the tests applied, the 

 stoppage of underflow by a submerged dam is the next step. To con- 

 struct this an excavation must be made across the stream bed to rock 

 or hard clay on the banks, and must be carried down to bed rock or 

 hardpan at the bottom of the channel. Ordinary precautions against 

 caving of the sides of this wide trench must be taken according to the 

 nature of the material found. The water must be temporarily dammed 

 and forced to flow through a pipe or box. Then the closest possible 

 contact must be secured by effecting a lodgment in impervious mate- 

 rial at the sides and bottom, and the dam should be constructed of 

 concrete rich in cement, the upstream face being well plastered with 

 cement or with a coating of asphaltum if available. When the work 

 has set well the temporary escape of the water may be stopped and 

 the loose material replaced on both sides of the dam. The top of the 

 dam usually rises sufficiently above the stream bed to hold back a cer- 

 tain depth of visible water (fig. 6), and to deliver it at a level where it 



