This paper is concerned with the actual comparison analysis for the freshening process in the two selected experimental reservoirs. At the deep freshening reservoir, salinity and depth of the freshwater layer were estimated by simulation technique using the quantitative equation for the two layered flow structures. First of all, it is shown that the effects of underdraiange conduit in the lower layer were reported more effective for the control of upper layer salinity comparing with the case of no underdraiange conduit. Further the results of computation were later compared with the real observed values and the relating parameters of the salt balance equation are conformed even though approximately. Finally it was represented that the salinity of upper layer is easily diluted not only by the tidal gate but also by the underdraiange conduit in the lower layer of the freshening reservoir.