1918] 



RURAL ENGINEERING. 



187 



cubic feet per second will be WN/62.5. If V represents the mean velocity of 

 the stream and 6 the breadth, then, when the average depth lies between b/10 

 and 3&/10, complete mixture occurs at a distance downstream=66 and at a 

 time when the addition of the chemical has continued at least 246/V seconds. 

 Samples must not be taken more than 6b/V seconds after the addition of the 

 chemical has ceased. These rules do not apply to streams whose averaf,'e depth 

 is less than b/10 ; then the point and time of sampling must be made by trial." 



A bibliography is included. 



Hydraulic conversion tables and convenient equivalents (U. S. Geol. Sur- 

 vey, Water-supply Paper 425-C (1917), pp. 7i-94).— Specially prepared tables 

 are given which afford a ready means of conversion between the terms in 

 common use in hydraulic computations. These should be of material assistance 

 to irrigation engineers. 



Ground water for irrigation in Lodgepole Valley, Wyoming and Nebraska, 

 O. E. Meinzer (U. S. Gcol. Survey, Water-Supply Paper 425-B (1917), pp. 37- 

 69, pis. 3, fig. 1). — This report deals with the underground waters of an area 

 of about 2,200 square miles in southwestern Nebraska and southeastern Wyom- 

 ing. Analyses of the waters are given which show them to be satisfactory for 

 irrigation and domestic use. Data concerning wells in Laramie County, Wyo., 

 and Kimball, Cheyenne, and Deuel Counties, Nebr., are also given. 



" Wells yielding enough water for practical irrigation can be obtained in most 

 parts of Lodgepole Valley and the total irrigated area could be considerably 

 increased by pumping. However, the area now irrigated is very large in com- 

 parison to the size of the stream, because ground water is supplied to the stream 

 during the irrigation season. Extensive pumping of ground water would re- 

 duce the available supply of stream water, although the decrease in stream 

 water would be less than the increase in pumped well water. Pumping on a 

 moderate scale will probably not appreciably reduce the supply of stream water 

 and is doubtless practicable in Lodgepole Valley. Flowing wells could prob- 

 ably be obtained by deep drilling in some parts of the valley, but the prospects 

 are not encouraging for obtaining supplies from deep wells in quantities or at 

 costs practicable for irrigation." 



In an appended article entitled Cost of Pumping for Irrigation in Western 

 Nebraska, data are reported by H. C. Diesem as summarized in the following 

 tables : 



Results of operating certain pumping plants in Nebraska in 191Jf. 



' Centrifugal pumps. Figure indicates number or size. H = 

 40111°— 18— No. 2 7 



horizontal, V= vertical, T— turbine. 



