46 On the Supply of Water 



supply into the Wormbete reservoir by way of Western 

 Creek (see map). By securing this additional quantity, I 

 ■would add upwards of ten thousand acres to the already 

 large gathering ground, thus making assurance doubly sure, 

 considering that in our variable climate, it is but prudent to 

 put beyond hazard, or even doubt, the question of supply, 

 by embracing all available sources within compass. 



Every attention has also been paid to the principal point 

 in reservoir construction, i.e. the natural impermeability of the 

 bottom, and which I have thoroughly ascertained by numerous 

 trial pits, which I ordered the chain and staff bearers to sink 

 to an average depth, whilst my assistants were otherwise em- 

 ployed in camp duties, plotting their field-work. 



Care has also been taken in selecting the site for an embank- 

 ment, within certain limits of deviation, — the foundation of 

 which must either be solid or capable of being made so,) — 

 having good natural abutments on either side of the valley, 

 at the shortest possible span, the height sufficient to impound 

 forty feet of clear water at centre of embankment, exclusive 

 of a subsiding depth of ten feet additional, considering, as 

 I do, that the great value of a reservoir, more particularly 

 in these latitudes, depends principally on its greatest cubical 

 contents with the least possible superficial evaporating 

 surface. 



To make this a certainty, and the more palpable to the ready 

 understanding of the commission, and that such may not be 

 altogether depending on the mere assertion of my verbal 

 opinion, I have had an accurate surface survey, longitudinal, 

 and numerous transverse sections, taken at every five chains, 

 across the valley, showing its converging sides, and giving at 

 same^ time the area of each cross section, and the means of 

 plotting accurate contour lines on the map, describing the 

 tortuous perimeter of the water levels at the three several 

 depths of forty, thirty, and twenty feet at embankment, 

 above the eduction pipe, thereby enabling me to come to as 

 close an approximation as may be of the separate cubical 

 quantities of water retained for use by each proposition. See 

 Table No. III. 



