Assisted management of water exchange in traditional semi-intensive aquaculture ponds

•A support system for the water exchange management in aquaculture has been developed.•Discharge capacity of grid gates has been investigated using a scaled model.•Five approaches were used to obtain the relationship for the discharge coefficient.•A generalized linear model provided the best fit with two non-dimensional parameters.•This model and the aquaculturist knowledge were integrated in a computer program.

Grid gates with multiple sharp-crested rectangular orifices are used to control manually water discharge from branch channels to semi-intensive aquaculture ponds. Experimental and analytical analysis related to the discharge characteristics of these grid gates under submerged flow conditions have been presented in this paper with the objective to integrate the results in an support system to control the water exchange management. Experimental analysis was carried out in the laboratory using a scaled model. Steady-state hydraulic data were measured and collected for each tested grid gate considering different orifices number and flow rates. Multiple linear regression (MLR), factorial regression (FR), polynomial regression (PR), hybrid model (PR + FR) and generalized linear model (GLM) were evaluated to determine the relationship between the coefficient of discharge Cd   and the non-dimensional parameters ω/h12, b/h1 and h3/h1 (ω is the total cross section of discharge; h1 is the upstream water level of the grid gate; h3 is the downstream water level of the grid gate; and b is the width of the channel) which were obtained by the analysis dimensional. Of all these approaches, the best fits were obtained using a FR + PR hybrid model and a GLM model with only two non-dimensional parameters ω/h12 and h3/h1 as independent variables. These models produced errors not higher than ±3%. The best GLM model and the aquaculturist knowledge in relation to the management of water exchange were integrated in a computer program namely ‘Gate management’ which was implemented in the ACUIGES system.