Pattern of Discharge and Mass Loading during Drainage of Excavated Ponds Used for Food Fish Production of Channel Catfish

Abstract

AbstractWe evaluated the temporal pattern of solids, organic matter, and nutrient concentrations in the discharge effluent of three commercial‐size excavated ponds with two types of drainage structures used in catfish production in Mississippi. Measurements of effluent water quality and pond stage elevation were used to calculate solids, organic matter, and nutrient mass loading when ponds were drained. Solids, organic matter, and nutrient concentrations in effluent from ponds with fixed internal drains were very high during the first 10– 30 min of pond draining. Thereafter, effluent solids and nutrient concentrations were similar to those of the bulk pond water. The initial flush of effluent contained solids that settle easily. Mass discharge was directly proportional to volume discharged in two ponds. In the third pond, mass discharge increased as a function of pond volume because poorly consolidated pond sediment exposed during draining was eroded by rainfall and wind‐generated waves. Average mass discharge (kg/ha) from draining the three ponds was as follows: total suspended solids = 976, 5‐d biochemical oxygen demand = 84, total nitrogen = 46, and total phosphorus = 3.5. These mass loading values can be annualized by dividing by the interval between pond drainings. Total annual mass loading can be calculated by adding annualized mass discharge from pond draining to mass discharge from pond overflow.