For our Water Supply. 245 
inches will represent the watershed as accurately as such a 
method of calculation will permit of. 
I think I am warranted, therefore, in concluding, that if 
we must place confidence in any estimate analogically elimi- 
nated from English data, we are not warranted in assuming 
a larger proportion of available rainfall for the Upper Plenty 
district that four inches. 
From Mr. Hodgkinson’s estimate of 11 feet 6°16 inches, 
we must therefore deduct one-fifth, or 2 feet 3°63 inches, 
which is equivalent to supply 62,500 at forty gallons per 
head per day. 
I also object to assuming sixty-two and half square miles 
as the area of the Plenty basin. 
Messrs. Acheson and Christy in their. report thought it 
safer to assume sixty square miles, and I followed their ex- 
ample in my estimate. 
This area has never been thoroughly surveyed, indeed the 
greater portion of the boundary line has never been visited 
‘ by any surveyor, being covered with an impenetrable scrub, 
and many thousand acres, according to Mr. Hodgkinson, 
consist of swampy and undrained lands, which are not only 
useless as affording no watershed, but they evaporate the 
watershed of many more thousand acres which drain into 
them. As it was of great importance to arrive at a safe 
and reliable result in this investigation, I think Mr. Hodg- 
kinson erred in assuming sixty-two and half square miles, 
and for the reasons which I have assigned, I think it will be 
readily admitted that it was much more correct to have as- 
sumed sixty square miles as the area of the Plenty basin. 
On this account, therefore, I have to deduct from Mr. 
Hodgkinson’s estimate 4°60 inches in the reservoir, which is 
equivalent to supply 10,454. 
2. Mr. Hodgkinson only allows 500 gallons per minute for 
the use of the district, and to maintain the flow in the river, 
and this is only equal to eight inches in the reservoir. Messrs. 
Acheson and Christy in their report allow twelve feet four 
inches for the same purpose ; so that they allow eighteen and 
half times the amount that he allows. 
They allowed this amount on the understanding that the 
Commissioners of Sewerage and Water Supply had entered 
into an arrangemeut with the resident population not to ab- 
stract more than one-half of the river, which was to be allowed 
to flow for twelve hours out of twenty-four. 
What will they say to the small amount accorded them by 
Mr. Hodgkinson? If his estimate of the discharge of the 
