82 On the Botany Watershed. 



its waters into the sea near Bunnerong. These waters may 

 easily be brought to the pumping station at Botany by a main 

 which should be laid for the purpose. 50 inches of rain falling 

 annually upon 1224 acres, will give on the average 3,804,041 

 gallons for every day during the last eleven years. Therefore 

 the average daily quantity of water falling on the Lachlan and 

 Botany Swamps being 13,205,368 gallons, and that on Long 

 Swamp, 3,804,041 gallons, we have had from the rainfall on the 

 Botany watershed a supply at the rate of 17,009,409 gallons on 

 the average for every day during the last eleven years. A 

 quantity, if conserved, that would supply nearly 35 gallons per 

 head per diem to a population of 486,000. We have used as 

 much per diem as six and a half millions of this quantity for 

 the present population, the remainder has necessarily run into 

 the sea to waste, because we have not had sufficient accommoda- 

 tion to conserve it. Having shown the average daily quantity 

 of water with which Pro^ddence has supplied us in the Botany 

 Avatershed during the last eleven years, and having had nearly 

 the same quantity this year to the 31st August, I think we may 

 fairly reckon on a similar quantity of rainfall in years to come. 



The next point to be shown is by what means we are to conserve 

 this quantity of water that now runs into the sea and make it 

 available for the use of the city and suburbs in the event of 

 drought, and also to meet the wants of an increasing population. 

 I will commence with that part of the Botany watershed north 

 of the Eandwick Koad, known as the Lachlan Reserve or Swamp. 

 There is already an embankment extending across the higher 

 part of this swamp which diverts the head waters of about 900 

 acres from their natural course, and leads them into Busby's 

 tunnel, through which they pass by gravitation into the city — 

 as before stated this quantity has lately been ascertained to 

 amount to 1,200,000 gallons daily. There are two places near 

 the eastern end of the tunnel, which undulates so that the 

 crown dips below the general level of the bed of tunnel, which 

 places are liable to become choked with the sand which drifts 

 through -the masonry of the shafts, so much so as to impede the 

 flow of water, and on one occasion to stop it entirely for several 

 days. These dips in the crown or soffit of the tunnel must be 

 cut away, and the crown so straightened as to admit a free 

 current at all times ; this, together with other necessary works 

 which should be done in the city to facilitate distribution and 

 increase consumption, from this source, would raise the flow 

 through the tunnel to two and half or three millions of gallons 

 per day, or 1095 millions of gallons per annum. For the supply 

 of the tunnel with this quantity at all seasons, it will be 

 necessary to construct an embankment along the northern side 



