MEASUREMENT OF WATER CIRCULATION IN PONDS WITH GYPSUM BLOCKS

The dissolution rates of gypsum blocks measured as weight loss after an exposure time of a few hours or a few days can be used as an index of water movement in aquaculture ponds. Weight loss from gypsum blocks increased linearly with increasing velocity of water flowing over the blocks. Weight loss was constant for an exposure time of at least 9 or 10 days. Rate of weight loss decreased with decreasing temperature and with increasing salinity. However, for conditions existing for freshwater and brackishwater ponds, the weight loss over an exposure period of 8-24 h can be easily measured. A method for preparing the gypsum blocks is presented and an example of their use is provided.