Observations of pond hydrodynamics

This paper provides a detailed observation of pond hydrodynamics. Bathymetr y and aerator deployment largely control the hydrodynamic regime. Aerators drive pond circulation, which is resisted by bottom and bank friction. Hydr odynamic friction is characterized by sediment grain size. One particular p ond is offered as a proxy representative of Australian mariculture ponds in general: Pond X. The pond had been stocked with P. monodon at densities in the range 25-35 m(-2) about ten times, during the period from 1989 to 1995 . Observations were made in the year 1996. The site was on the east coast o f Australia at 18 degrees south latitude. The location was sheltered by a m ountainous offshore island, such that winds effecting the pond averaged 2.3 m s(-1). Water exchange occurred at a rate of about 8.3% of pond capacity per day. Pond X was found to be rectangular, 120 m long and 87 m wide. The banks were found to slope between 1:1.5 and 1.7.6, with an average slope ne ar 1:3. The pond was shallowest in one corner, where depth was 834 mm, and drained diagonally with 1872-mm maximum water depth. Aeration was provided by a total of I;ix 1.5-kW machines, comprised of two of the paddlewheel typ e and four of the propeller-aspirator type. Each machine was found to deliv er 200 N of horizontal thrust into the pond water column. The combined effe ct of the aerators created a circulation current averaging about 11 cm s(-1 ) around the pond periphery. The central region of the pond was found to ha ve a fluctuating velocity of less than 1 cm s(-1). The mass-average size of pond soil and sediment was found to vary from 25 mu m in the central regio n to 250 mu m at the banks and where the bottom was swept by paddlewheels. (C) 2000 Elsevier Science B.V. All rights reserved.