BemarTcs on the Beport of the Water Commission. 71 



gallons per day. They also examined the upper part of the 

 George's River, and found it delivering nearly two million gallons 

 per day, " the period being rather dry." We may conclude from 

 this, that even in dry seasons there would always be some contri- 

 butions going on to the George's Eiver reservoir, as the streams 

 examined were only two out of several. 



Secondly, if even the George's Eiver should become dry, we 

 may be quite sure, that in the same season the reservoir at 

 Prospect would have been dry much sooner, and therefore, on a 

 comparison of the two schemes, the Prospect reservoir would not 

 show to advantage. Thirdly, the present delivery at Sydney does 

 not exceed four million gallons per day, and though it was quite 

 proper in the Commissioners to make provision for a future 

 delivery of 12,000,000 gallons, still it would only be gradually 

 that such a demand would arise. At 4,000,000 gallons per day, 

 the George's Eiver reservoir would hold out for 2000 days 

 (assuming of course my calculation that it would hold 8,000 

 million gallons is not excessive, and leaving out of count loss by 

 evaporation) without any addition being made to its supply. 

 This is provision for a contingency such as the history of the 

 colony has never yet known, and such as the Upper Nepean 

 scheme would not be better able to weather. It must be remem- 

 bered too, that even in what is called a drought there are 

 occasional showers, especially on the sea coast. The Commis- 

 sioners' figures show that the flow down the ISTepean at the 

 Cataract was equal to more than one-third of the estimated 

 rainfall, and if the George's Eiver reservoir would catch one-third 

 of all that fell on its watershed it would be replenished at every 

 rainfall, even though some extra allowance should be made in a 

 dry season for absorption. 



And lastly, before any such contingency could arise, or even 

 before the reservoir could be reduced materially below the level 

 of neap low tides, I think we may safely assume that the dam 

 would become so thoroughly consolidated as to be impermeable^ 



Even if the George's Eiver reservoir should become empty 

 and the last drop be pumped out, its bed would only be in the 

 same relative position as Lake Haarlem and a large part of 

 Holland, which is below the sea level, and protected only by 

 embankments. It may be urged however, that in such a state of 

 things, even if the dam should be impermeable, the boundary 

 rocks might not be so, and that through the fissures of the sand- 

 stone salt water might ooze. It is said that at Botany, when the 

 engine-pond has been very low, sea-water has thus percolated 

 through the barrier of sand and rock that separates the pond 

 from the sea, although Mr. Bell, the City Engineer, denies that 

 this has been the case. 



