Aquaculture Engineering

Design of ponds - Bottom slope of pond

Unit 4- Layout planning of fish ponds

Design of ponds

Bottom slope of pond
For intensive and semi-intensive culture system, regular flat bottom pond bed with uniform slope is preferred. In case of extensive farming, pond bed maybe designed with trenches which cover usually 20 to 25 percent of the total pond area. Trenches are designed to have a total water depth of normally 1m while, the rest of the pond area may have approximately 0.6 to 0.75 m of water depth. Trenches provide protection against birds and shelter from high temperature during the day. During pond construction, soils from these trenches are utilized in dike construction. This reduces the cost of dike construction because of reduced lead in soil movement, as well as avoids the loss of more fertile top soil which otherwise is used in construction of pond dike. The depth of excavation for those trenches and their width are decided taking into consideration the requirement of volume of soil in dyke construction. The bed level of those trenches should be designed so as to drain off the water completely from them during the pond drying. The pond bottom is provided a slope between 1000:1 to 1000:5 towards the drain to facilitate the water flow during harvest and pond drainage. The pond bottom should be designed so as to remain above the ground water table which is necessary for effective drying of pond bottom during pond preparation. A coastal aquaculture pond is normally designed for a water depth of 1 to 1.5m depending upon the species of fish to be cultured, location and various other factors.