XL. T. W. KEELE. 
of increase in the population for 10 years from 1896-7 to 
1906-7, viz., from 418,512 to 603,910, be taken, it will have 
increased in 1912-13 to 715,000; but the rate of increase 
for four years from 1902-3 to 1906-7 has been more rapid, 
viz., from 523,000 to 603,910, and if this be continued, the 
population supplied with water in 1912-13 will have in- 
creased to 725,000. The present rate of consumption per 
head per day is about 40 gallons, which is low, owing to 
the necessity for economy in the use of water during the 
long drought, but the restrictions having been removed 
there can be little doubt that the consumption will increase 
very rapidly, and at the end of the good seasons in 1912-13, 
it would not be unreasonable to assume that it will have 
increased to at least 60 gallons per head per day. The 
population then being probably 725,000 will require an 
average supply daily of 433 million gallons. If there is 
anything in periodicity of rainfall, and I think most people 
will now admit that there is something in it, then the year 
1913-14 will mark the first year of a long period of declining 
rainfall, and the diagram shows that the first year is usually 
exceedingly low. The supply would then depend almost 
wholly upon the storage in the reservoirs. 
Behaviour of Reservoirs during Wet and Dry Seasons.— 
Let us see how they will be likely to stand the drain 
about to be made upon them. Assuming the rate of 
increase in the population to be maintained, and the con- 
sumption to be 60 gallons per head, the figures will be, 
population 745,000 and consumption 44} million gallons per 
day in 1913-14. To the latter must be added the loss by 
evaporation from the surface of the two reservoirs which 
will cause the draft upon them to amount to 52% million 
gallons per day. If we assume for the moment that no | 
addition to the storage is made, the entire quantity of 
21,000 million gallons in Cataract and 11,000 million gallons 
in Prospect reservoirs or a total of 32,000 million gallons 
