616 "Proceedings of Royal Society of Edinburgh. [suss. 
Note on the Rainfall on the Drainage Area of the 
Talla Reservoir. By B. Hall Blyth and W. A. Tait. 
(With a Map.) 
(MS. received January 28, 1905. Read May 1, 1905.) 
In 1895 the Edinburgh and District Water Trustees obtained 
an Act of Parliament for the introduction of a new water supply 
to the city of Edinburgh drawn from the Talla Water, one of the 
upper tributaries of the river Tweed. 
The Bill as originally introduced contained provisions for giving 
off 4,000,000 gallons a day as compensation to the stream, and for 
appropriating the remainder of the water. 
The Tweed Salmon Fisheries Commissioners and other pro- 
prietors interested were advised that the proposed amount of com- 
pensation was too small, and after various negotiations a clause was 
ultimately adjusted providing that rain gaugings should be taken 
over the drainage area for a period of seven years from the 1st Janu- 
ary 1 896 by the authors of this note (Mr Tait having been appointed 
in lieu of his predecessor), and that thereafter they should fix — tak- 
ing all the circumstances into consideration — what was the avail- 
able annual rainfall of the district. One-third of this ascertained 
quantity was then to be given as compensation to the stream, the 
remaining two-thirds being appropriated for the supply of the city. 
To carry out these provisions, seven gauges were placed on the 
drainage area at varying altitudes. 
The drainage area and the positions of these gauges are shown 
on the accompanying Ordnance Map, and the heights above 
Ordnance datum are as under — 
The top water level of the reservoir is 950 feet above Ordnance 
datum. 
Monthly readings were taken at all the gauges for seven years 
from January 1896, and in addition, at the three last-named 
stations, which were easily accessible, daily readings were taken 
from independent gauges. 
The results of these are given in the following table : — 
1496*05 feet. 
2627-34 „ 
2258-28 „ 
1859-92 „ 
No. 5 . 
„ 6 . 
1537-59 feet. 
966-03 „ 
1196-48 „ 
