LXVIII. R. T. McKAY. 
the run-off represents 26 inches, whereas with a similar 
rainfall on the catchment of the Ovens River at Wanga- 
ratta, the run-off represents 10 inches. 
Monthly Run-off and Rainfall over Murrumbidgee Catch- 
ment at Gundagai for the Years 1900-1904.—For the 
purposes of showing the difficulty in arriving at any definite 
conclusion as to the relation between monthly rainfall and 
monthly run-off, over any extensive gathering ground, the 
author has compiled the following table and diagram— 
Appendix ““G’’—for the years 1900-1904. As previously 
referred to in this paper, the source of the Murrumbidgee 
is many miles away from the gauging site at Gundagai, 
and as the catchment is a very extensive one, the effect of 
precipitation on the mountains is not felt at the gauging 
Station until some weeks later. It is apparent that when 
estimates of run-off are prepared for such a large area, the 
period for the computations should extend over several 
years. By reference to the table, it shows that a higher 
percentage of rainfall is discharged during the months from 
June to November, when the grounds have become satur- 
ated after the winter rains and evaporation is at a minimum, 
A peculiar circumstance occurs in regard to the table for 
the month of October, 1900, wherein the measured discharge 
at Gundagai amounted to 297%, or approximately three 
times the precipitation for that month, over the whole of 
the gathering grounds. This remarkable phenomenon is 
undoubtedly due to the abundant rains during the previous 
four months which completely saturated the soil, and the 
flow of ground water was maintained long after the cessa- 
tion of rain over the catchment. There are also numerous 
instances in this table which amply demonstrate that an 
interval of two weeks or even more may elapse between 
the precipitation and its flow past the gauging station at 
Gundagai. 
