152 



FLOODS AT THK MANCHESTER WATERWOEKS 



through the pipes, I believe to be very near the truth — 

 rather under than over ; but the Woodhead Reservoir afforded 

 means for still more accurate observation. Here nearly 

 all the water which reached the reservoir was impounded ; 

 and, as the capacity of each reservoir had been previously 

 ascertained by careful survey and measurement, for every 

 foot in depth, there can be no doubt as to the quantity 

 of water received. 



From eleven o'clock on the morning of the 4th till twelve 

 o'clock at midnight on the 5th, a period of 37 hours, the 

 quantity of water impounded in the reservoir was 75,720,000 

 cubic feet, and the quantity discharged 12,168,000, — making 

 the total quantity received 87,888,000 cubic feet = 3| inches 

 of rain over the drainage ground of the reservoir. 



From eleven o'clock on the morning of the 4th to the same 

 hour on the morning of the 5th, the quantity impounded was 

 02,000,000 cubic feet, and the quantity discharged 3,528,000, 

 making the total quantity received in 24 hours, from 7,500 

 acres of ground, 65,528,000 cubic feet, being equal to 2y^ 

 inches of rain. The rain at Crowden during this period 

 appears to have been S^V To allow for the water which 

 still remained to flow off the ground before the streams 

 would regain their usual volume, we must add -^g of an inch, 

 (after allowing for the natural flow,) making the total quantity 

 of rain which fell in 24 hours, as measured by the Woodhead 

 Reservoir, 2-^-^ inches. 



The rain which was discharged at Rhodes Wood, or im- 

 pounded in that reservoir and Torside in the same time, 

 exclusive of what was received from Woodhead, amounted 

 to about 66,000,000 cubic feet of water from 7,900 acres, 

 being, as nearly as may be, the same quantity per acre as that 

 received at Woodhead. The calculations may, therefore, 

 be taken to show accurately the quantity of water which 

 flowed down the river during this extraordinary rain ; show- 

 ing also, that the average rain over the district, taking the 



