232 Bulletin 37. 



water they needed was evidently available. The total loss dur- 

 ing the season equaled a depth of about 20 inches of water over 

 the orchard, of which about 80 per cent was lost during the first 

 three months, about 16 per cent the next three months, and only 

 about 4 per cent the last three months. 



It seems to be a warrantable conclusion from the facts dis- 

 cussed above that the loss of water from the leaves of orchard 

 trees is comparatively light after the trees have made their 

 growth, the amount exhaled (and consequently the amount need- 

 ed) gradually diminishing as the summer season advances. As 

 indicated by the investigation of underground conditions (men- 

 tioned on page 219) deciduous orchard trees in our climate begin 

 using water early in February. From this date until about the 

 end of June the amount used evidently gradually increases, and 

 after the latter date evidently gradually diminishes. These facts 

 indicate plainly that much of the water should be applied as soon 

 after the first of January as possible. 



Effects of Changes in Level of Ground Water. 



It will be observed by referring to Table I that during the 

 summer of 1899 the stratum below the 25th foot lost considerable 

 moisture, notwithstanding the fact that the 5-foot stratum above 

 gained moisture during the same period. This was evidently 

 due to the lowering of the level of the ground water, as the wa- 

 ter in all of the wells of the region fell during this season. The 

 comparatively light rainfall both in the valleys and in the moun- 

 tains during the preceding one and one-half years was undoubt- 

 edly the cause of this fall in the level of the ground water. On 

 account of the coarse gravel encountered in the 34th foot, it was 

 impracticable to bore to ground water after June, 1899. But if 

 this could have been done, it would probably have been ascer- 

 tained that at the same distance from the water level the condi- 

 tions would have been practically the same at the end of the 

 season as at the beginning, the water of the stratum above hav- 

 ing simply settled and adjusted itself to the changing position of 

 the ground water. During the winter of 1899-0 the lower eight 

 feet gained a little in moisture as the water level raised slightly, 

 and lost a little again during the succeeding summer, as the wa- 



