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Frequently Asked Questions 

Q.  Have you built a prototype?

A.  No, though the oil industry has proven the design of a seaworthy boom with a curtain wall as seen by the image on the reservoir main page.  What needs to be demonstrated is a practical  rainwater catchment system in a river mouth. Also the halocline effect needs to be researched to ensure the sea water dos not diffuse to much into the fresh water.  

Q.   What will this solution cost?

A.     The infrastructure of an off shore reservoir would be much lower cost compared to land based reservoirs.  Land based reservoirs need to hold back tons of water, an off shore reservoir needs only a thin membrane to retain that fresh water. Land based dams cost millions of pounds to build and require large amounts of land to be purchased.   


Q.  Would the boom be affected in storms ?
A.   During severe storms the whole reservoir can be submerged by 5 to 10meters to avoid damage. This would be done by reducing the air pressure in the boom segments which reduces their buoyancy.

The whole system would not touch the sea bed as weights placed at 5 m intervals around the bottom of the curtain wall and 3 M below the bottom of the curtain wall would be allowed to touch the bottom .

 If the depth of water is greater than 50m then these extra weights would not be required.

Q.   Would shipping  be affected by these large reservoirs? 

A.  Chosen sites would need to be away from shipping lanes .

Q.   What is a Halocline?

In oceanography, a Halocline is a strong, vertical salinity gradient. Because salinity (in concert with temperature) affects the density of seawater, it can play a role in its vertical stratification. Increasing salinity by one kg/m3 results in an increase of seawater density of around 0.7 kg/m3.

 In the mid latitudes, an excess of evaporation over precipitation leads to surface waters being saltier than deep waters. In such regions, the vertical stratification is due to surface waters being warmer than deep waters and the halocline is destabilizing. Such regions may be prone to salt fingering, a process which results in the preferential mixing of salinity.

 In certain high latitude regions (such as the Arctic Ocean, Bering Sea, and the Southern Ocean) the surface waters are actually colder than the deep waters and the halocline is responsible for maintaining water column stability- isolating the surface waters from the deep waters. In these regions, the halocline is important in allowing for the formation of sea ice, and limiting the escape of carbon dioxide to the atmosphere. Haloclines are also found in fjords, and poorly mixed estuaries where fresh water is deposited at the ocean surface.

 A halocline can be easily created and observed in a drinking glass or other clear vessel. If fresh water is slowly poured over a quantity of salt water, using a spoon held horizontally at water-level to prevent mixing, a hazy interface layer, the halocline, will soon be visible due to the varying index of refraction across the boundary.

Q.  Can you site these reservoirs at the majority of river mouths?

No but perhaps 1 in 5 river mouths. The criteria being : to allow for vertical tidal range the bottom of the curtain wall should be 5M above the sea bed at low tide.  Thus a minimum 30M depth at low water is advisable.

 To allow for tidal currents, the reservoir should be placed away from currents in excess of 3 knots. 


Q.   How durable will the reservoir  be?

A.   The boom would require 6 monthly checks  but it is envisaged that one section at a time can be replaced when needed without compromising the containment of fresh water. Other parts of the reservoir are very durable. 

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 Last modified: 11th Oct 2007
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