1879. ] Discharge of large Rivers in Assam. 15 
portion, the extreme flood of the Brahmaputra at the Brahmakund would 
_ be not less than 200,000 cubic feet per second. 
Before closing work at Tengapani-muk I thought it well to make a mea- 
surement of the united stream of the Tengapani and Noa Dihing rivers. 
This I did on the 6th April 1878 at a site 200 yards below the junction 
of the Tengapaéni and Noa Dihing rivers. At the time of measurement the 
water was fully 3 feet above mean low level of the year, and more than half 
of it came from the Noa Dihing river. 
For the section 18 soundings were made, observations for velocity 
were taken at 2 stations and there were 19 recorded passages of the floating 
instruments. 
The measured discharge was found to be 6,807 cubic feet per second, 
sectional area 2,203 superficial feet, mean velocity 3°1 feet per second. 
At the time of measurement the river was 3 feet above minimum level 
of the year ; it is computed that for the low level of the year the discharge 
is 3,000 cubic feet, area of section 900 superficial feet, and velocity 3°3 feet 
per second; and of this 3,000 cubic feet, 2,500 cubic feet comes from the 
Tengapani river. 
For an ordinary high flood rise of 15 feet, the discharge is computed 
to be 53,000 cubic feet per second, sectional area 10,400 superficial feet and 
mean velocity 5:1 feet per second. 
For an extreme flood rise of 18 feet, the discharge is 65,000 cubic feet, 
sectional area 12,800 superficial feet and mean velocity 5:1 feet per second. 
From the Synopsis Table attached, it will be seen how closely the sum 
of the volumes &c. observed, for the two great streams which form the 
Brahmaputra River, agree with the observed volume of the river at 
Dibrugarh. , The river at Dibrugarh should be of greater volume than the 
combined Dihang and Sadiya streams, because of the Lali channel of the 
Dihang which joins in just below the place where the section of the Dihang 
and Dibang wastaken. During the cold season, and at time of observations 
it was a small and fordable stream 100 yards wide, but during floods the 
channel brings down a very large volume of water. 
During the floods a considerable volume of water passes down the 
Buri Suti, the mouth of which is on the north bank and between Dibrugarh 
and the mouth of the Dihang river. 
The Buri Suti falls into the Brahmaputra near the mouth of the Dihing 
river, south of Dibrugarh. 
I have endeavoured to be as moderate as possible in my estimates of 
the flood discharges, but I think it may fairly be stated that at Poba, a 
few miles above the mouth of the Buri Suti, there is every season a 
flood when 1} million cubic feet per second passes down the Brahmaputra. 
The rise of the flood I have calculated at 15 to 18 feet. The rise at 
Gauhati is 28 to 30 feet. 
