You don't list your Location or Country, which you can easily do in your Profile, and would be especially helpful to people replying to a Question such as yours.
If the water tower is built of reinforced concrete, it is very important to fit a proper lightning arrester system.
I have not seen the design of water tower you are thinking of, or are building, and a diagram or plan/picture here, with some dimensions would be helpful.
The Ground resistance at the base of the tower is important that this be lowered as much as possible, and, once again, I do not know the nature of the ground where you are writing about, but this is normally done by an Earth Mat, with a ring of circumferentially connected and driven Earth Rods..
Thus I can only give general advice, until some missing details are supplied.
General:
The "early Streamer" device emits streams of charged ions from the upwards facing pointed electrode tips.
Before the main discharge of lightning, the charged cloud emits a ground-seeking streamer of voltage which may exist for several minutes, extending itself towards the ground, or any object which is higher, even though a poor conductor, helped by rain, should that be falling at the time.
The downwards travelling streamer eventually makes near contact with the ground, ionising the air during that travel downwards.
This is why at times, people have had the hair stand up on their head, because of the higher than normal Voltage field (Normal Planetary electrostatic field is approximately 1000 Volts per Metre, vertically for some 20,000 feet) - and if you ever have your hair stand on end, with a large cloud overhead, you may have less than a second to fall flat, to minimise a lightning shock to yourself.
When that downwards travelling streamer makes full contact with the ground, or grounded object, because the ionised air is conductive, the main discharge happens immediately, perhaps several million Amperes at 20,000,000 Volts or more = Huge energy transport in a few seconds.
The air outside the discharge cloud is instantly heated to plasma state, perhaps 1,000,000 Degrees Celsius or more, and the rapid expansion causes the Thunder sound.
If you are very close to a lightning strike, a few Metres away, and are not injured, you find that you never heard the thunder, but you heard the discharge, which has the typical sound of "tearing calico", and having been in that situation several times during a dry thunderstorm, before the heavy raindrops started falling, it is rather a frightening sound.
Induced charges are minimised, by all reinforcing steel having welded joints, and being properly bonded to the Earth Mat, at Tower base.
Building Protection (Your Water Tower).
The Earth Mat is welded copper conductors, in a 600mm x 600mm square grid form, cross-sectional area of conductors being 1 inch diameter or equivalent, with driven hot dip galvanised/copper/stainless steel electrodes, dependent on local soil corrosiveness.
All joints are welded and crimped/bolted/riveted, dependent on the type of mat conductor being used.
The Earth Mat distance extended outwards from the tower base is determined by:
Annual number of Lightning days in the area
Height of Tower
Resistance of soil
Whether other buildings are located in the vicinity.
Other factors as advised
Flat electrical busbar grade Copper strip 100mm wide x 6mm thick is run around 4 sides of the tower, upwards all joints welded using "Silfos" or similar welding wire. Each joint is also bolted or riveted before welding.
The vertical strips run to the top of the tower, as straight as possible, with no sharp corners, and if there is a single point higher than any other, all go there and are connected together, welded + riveted/bolted.
The "Streamer device" normally fits at the tower top, to radiate upwards the ionised streamers.
The energy contained in the average lightning strike may be enough (if carefully and instantly capable of being safely stored), to meet the demands of a large city for several months.
That's a short summary, and trust it assists you.
Should you wish further please
Kind Regards....
__________________
"The number of inventions increases faster than the need for them at the time" - SparkY
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