226 GEOLOGICAL HISTORY OF LAKE LAHONTAN. 



Commencing with the simplest instance, we have in the case of Walker 

 Lake an inclosed water-body which receives its entire supply from the 

 Walker River. The total quantity of saline matter contained in the lake 

 water is 13.89 times as great as in an equal volume of river water. It fol- 

 lows, therefore, that nearly fourteen times the present volume of Walker 

 Lake has been evaporated in order to bring the waters to their present 

 degree of salinity. If we know the average annual influx, we can deter- 

 mine the length of time required to bring the lake to its present density. 

 From the very few measurements available, we have assumed 200 cubic 

 feet per second, or 700,000,000 cubic yards per annum, as the average dis- 

 charge of the Walker River at the present time (see page 44). The vol- 

 ume of the lake, as determined from the data given on Plate XV, is 

 13,159,000,000 cubic yards. It would therefore require between eighteen 

 and nineteen years for the river to supply water enough to fill the lake 

 basin to its present extent. As the total saline content of the lake amounts 

 to about fourteen times what would be contained in an equal bulk of 

 river water, it would require 260 years for the river, with its present vol- 

 ume, to supply the amount of saline matter now dissolved in the lake, 

 provided there had been no loss of the salts contributed. Observations 

 have shown, however, that calcium carbonate is being deposited from the 

 waters of the lake. A comparison of the analyses of the lake and river 

 waters given on pages 46 and 70, shows that there is even less of this 

 salt in the lake than in an equal volume of the river watei\ All of the 

 calcium now contributed is apparently at once precipitated. The remain- 

 ing salts occurring in the lake are more soluble than calcium carbonate, 

 and we have no reason to suppose that any of them are being precipitated 

 Dropping calcium carbonate from the analyses, and considering the re- 

 maining salts only, we learn that in these the lake is 19.66 times as rich as 

 the river waters. Making the computation as before, but using the last 

 mentioned value for the relative salinity of the lake and river, we find that 

 it would require 343 years for the river to supply the amount of salt now 

 contained in the lake. 



Approaching the question in another manner, it is evident that we may 

 determine the annual inflow, providing the annual evaporation is known, 



