2 - TECHNICAL REQUIREMENTS

The basic requirements, as concern the lay-out and the various topographic and hydraulic levels, are shown in the 2 plans 58 004 and 58 007.

2.1. The water storage pond

It is required in case the water intake is not possible during the whole tide cycle, i.e. for tidal amplitude above 1 metre.

2.2. Grow-out ponds

• The rectangular shape is preferable, as it would increase the water movements from one end to the other, not leaving large areas unaffected by water renewal. Suggested size is 125 m × 80 m;

• There should be a slope of the pond bed, about 3/1000, from the inlet to the outlet structure. If not feasible, a sloping internal drain will have to be dug out, in order to facilitate harvesting. The average depth of water should be one metre;

• It is essential to have opposed water inlet and outlet control structures (one each), allowing water filtration and easy adjustement of level.

  The typical, universally used structure is called “monk sluice”, made of reinforced concrete, with Hume type culverts.

This sluice gate is necessary at the outlet of the pond, for :

• an easy adjustement of the water level in the pond,
• a possibility of “flushing” accumulation of reduced rotten matter,
• easy harvesting, by gravity drainage of the whole content of the pond (water + shrimp) into a net.

It is also very convenient to have such a structure as an inlet gate, for easy handling of water renewal.

For a 1 ha pond, the “Hume” pipe diameter should be :

• 300 mm at the inlet,
• 500 to 600 mm at the outlet.

2.3. Pregrowing ponds

Rectangular shape is to be preferred, for efficiency of water movements.

Suggested size is 80 m × 15 m. A slope of 3/1000 is to be given to the pond bed, for an easy and quick harvest of juveniles.

2.4. Water requirements

For a semi-intensive farm of 20 ponds of 1 ha each, and 5 ponds of 1 200 m², computation of daily water exchange should be :

• 95 % grow out ponds at 10 %/day;
• 5 % grow out ponds at 50 %/day;
• 80 % pregrowing ponds at 10 %/day ;
• 20 % pregrowing ponds at 50 %/day.

Which amounts to 12 % average daily water renewal for the whole farm. Depending on the site topographic and tidal characteristics, the water can be either gravity fed, or pumped.

2.5. Other installations

Besides the ponds, and the water intake structure, or the pumping station, following installations are required, to be within a small, service building :

• a small office,

• a room for storage of feed and equipments (nets, …) ;

• an area for cleaning of the harvest before dispatching…

• a small workshop ;

• if possible an ice-making machine.

POSSIBLE PRE-SELECTED SITES

HS Mean High Water Spring
HN Mean High Water Neap
LN Mean Low Water Neap
LS Mean Low Water Spring