In England, where supplies of Water depend on Storage Capacity in Impounding Reservoirs ... this Capacity is provided for not less than 200 days and up to 300 days and even with the largest provision several dry years following will starve the district - that is, the water stored may become Exhausted.
For Hong Kong to have 300 Days storage of water there should be 450 Millions of Gallons of Storage room to supply 15 Millions of Gallons per Day.
But the Meteorological Conditions of Hong-Kong may require even double this Storage Capacity, or 900 Millions of Gallons:
Some new Impounding Reservoirs in India both for Bombay and for Madras, though very large, prove, in use, to be much too small.
For a full and abundant supply of Water, by Storing there must be Capacity - To provide this most cheaply, nature must have arranged favorable sites for short Embankments, as long and deep Embankments, made of Earth, are necessarily very Costly to Construct: and, in a Country subjected to occasional violent falls of rain may be very dangerous, there must, in such cases, be ample overflow Byewash space constructed in and down the Solid ground, The fall being in vertical steps of about 4 Feet, In no case should a sloping Byewash be made.
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Full information is required from Hong Kong as to the Capacity of the Reservoir recently constructed, and its Cost.
As to the Area of Gathering Ground above it, and the dry Weather volume of any Stream or Spring flowing into it.
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Information required as to Rainfall.
1. Heaviest in shortest time.
2. Longest periods of drought.
3. Longest periods small Streams remain dry.
4. Least volume of Water in Streams in driest Season.
5. Greatest volumes in wettest Seasons.
6. Vertical height to which the water rises in streams from the driest State to the most extreme flood.
Effects of violent Floods - in the district & Areas inundated.
This information, if properly obtained and sent over to England, will enable reliable advice to be given; as to the Existing works, and as to future works.
If there is any river source available, but where Steam Engine pumping power and filtration would be necessary, such source may be indicated... as Pumping may be more economical than the Construction of Impounding Reservoirs, At Calcutta water is drawn from the Hooghly river - is filtered - pumped by Steam Engine power and so supplied to the City and Suburbs of Calcutta.
In England it is frequently found to be cheaper to use Steam Engine power to pump water from Rivers nearer to the Population.
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