VAIN WY KCS 2 DEY. 
By Mr. GaAarRwoop ALSTON. 
[READ 28TH OCTOBER, 1891.] 
Tue large dam at Van Wyk’s Vley was designed and constructed 
by and under our late Hydraulic Engineer, J. G. Gamble, Esq., and 
was completed in 1883, the distributing furrow was made in the 
summer of 1884-5, and the arable lands were first put under culti- 
vation in 1885. 
Van Wyk’s Vley is situated about fifty miles north of Uarnarvon, 
being about one hundred and twenty miles from Victoria West, and 
the main road to Kenhardt and Upington runs over the farm. The 
dam is placed on an affluent of the main river draining the Carnarvon 
Division and about seven miles above the junction of the two streams. 
The cultivated lands are in the triangle formed by the two streams 
and the available area is very great, probably two thousand morgen 
within the triangle and another two thousand on the right bank of 
the main stream and away below the junction. : 
The “ supply furrow,” of which I hand in photographs, connects 
the main stream with the dam and is run at such a level as to 
discharge into the dam at a little below high water mark. For the 
lower two miles of its course it runs almost parallel to the main 
distributing channel but of course the waters flow in opposite directions. 
The dam wall is 33 feet in height and I think 980 feet 
in length, about 10 feet broad on top and 175 feet at the base. For 
accurate dimensions I refer you to one of Mr. Gamble’s reports 
where excellent plans and sections of the work are given. It is 
calculated that if filled to the depth of 27 feet (measuring to 
the sill of the discharge pipe) the reservoir will contain 35,090,000,000 
gallons—thirty-five thousand millions! say seven hundred times as 
much as can be stored by all the Cape Town reservoirs together, or 
eighty times as much as the Beaufort West dam can contain. 
The water service is regulated from a tower similar to that in 
the Molteno reservoir, the main distributing furrow is upwards of 
six miles in length, the branch fuirow serving the village is two 
