Director Ambekar E. Eknath, Ph. D Head, APED J.K. Jena, Ph. D ...

Pond Depth
.Depth of a pond has an important bearing on the physical and chemical
parameter of water. It is established that below 3-4 m water, there IS not
much photosynthetic activity to keep the deeper water oxygenated and
water temperature is low containing less plankton.
.As per the present state of culture practices, suitable pond depths excluding
free board are suggested below:
Ponds
Small oonds
Depth of pond (m)
Water loaqedlirriqated areas Rain fed (plains and hills)
Free Board
.Free board IS the additional height of the pond dyke above maximum water
level. It is generally provided as safety factor to prevent overtopping from
wave action, heavy ra~nfall and for other causes. It is the vertical distance
between the elevation of the water surface in the pond at deslgned depth
and the elevation of dyke1 embankment after dyke settlement. A free-board
of 0.5-1.0m is usually necessary to keep the carps1 prawns safe from water
management point of view. Therefore, in culture ponds at maximum water
level an ovefflow or outlet arrangement is provided.
Pond Dyke
.The design of the dyke should be strong enough to hold the water upto the
maximum level and be safe against hydraulic pressure. The stability of the
dyke should be checked by drawing the hydraulic gradient line (slope of
seepage line). The base should be sufficiently wide, so that the seepage
line do not appear above the toe on the downstream side of dyke. It is
desirable to have earth of about 0.3-1.0m above at downstream of the dyke
to guard against any percolation through the dyke. The base width at bottom
of dyke on the depth of water in pond and top width depends on the type of
soil.
Tvoe of soil Slope of seepaae line (hlv 1
Clav soil 3.1
sandy loam soil 5.1
Sandy soil 6.1