abstracts: geology and engineering 451 



has a steadily expanding field in the collection of stream-flow data, 

 both for statistical purposes and as a basis for the design of various 

 kinds of hydraulic works, in drainage investigations, in the operation 

 of irrigation systems in the arid regions, in the determination of hydrau- 

 lic constants and coefficients, in the testing and operation of water- 

 power plants, and in other directions. 



Ground water in Big Smoky Valley, Nevada. O. E. Meinzer. Big 

 Smoky Valley is a typical desert valley occupying a closed basin of 

 3250 square miles. Numerous beach ridges and embankments, 50 feet 

 in maximum height, show that in the Pleistocene epoch this valley 

 contained two lakes — Lake Toyabe, which covered 225 square miles, 

 and Lake Tonopah, which covered 85 square miles. The alluvial 

 slopes are broken by fault scarps, indicating maximum displacements of 

 more than 100 feet. Nearly 50 small mountain streams discharge into 

 the valley, 10 of which, according to measurements made in October, 

 1914, contribute 7000 acre-feet a year to the ground-water supply. 

 Ground water is discharged into the atmosphere from two areas which 

 together cover about 205 square miles. These areas were mapped on 

 the basis of (1) soil moisture and position of the water table, (2) soluble 

 salts at the surface and in the soil, and (3) native plants that feed on 

 ground water. 



A method of correcting river discharge for a changing stage. B. E. 

 Jones. When a river is rising fast it has a greater velocity and a 

 greater discharge than it has at the same height when its stage is con- 

 stant. This is caused by the increase in slope due to the rising stage. 

 Likewise, when it is falling fast it has a lower velocity and a lower 

 discharge. A formula is obtained for comparing the discharge under 

 changing stage conditions with that under constant stage conditions, 

 as follows: 



The change in slope is assumed equal to the change in stage per 

 second divided by the distance the water travels per second. Then 

 as the discharge varies as the square root of the slope, the relation 

 of the discharge under constant stage conditions (Qi) to the discharge 

 under changing stage conditions (Q 2 ) would be 



^ 2 ^ / c u ra ^ e °f cnan 9 e °f s ^ a Q e 



^S 1 



velocity 

 Si in the equation is the surface slope under constant stage conditions. 



