Aquatic ecosystems play an important role in biodiversity, the economy and people's livelihoods. Proper management of the reservoirs behind the dams, as one of these important and man-made ecosystems, requires sufficient information about their lithological characteristics. Because, a correct understanding of water quality can lead to sustainable development and protection of the aquatic ecosystem. Knowing the quality of water is essential to adopting appropriate solutions to prevent or improve quality. Raisali Delvari Reservoir Dam, which is almost 10 years old, is one of the young reservoir lakes in the country, which is located in Bushehr province and has not been studied by liminology. Permanent monitoring and study of the process of physical, chemical and biological changes of man-made lakes can be used as a model to illustrate the process of formation of cycles of materials and biological communities of natural lakes. In order to estimate the qualitative indicators of NSFWQI, IRWQI and Shannon-Wiener, Simpson and Margalf diversity indicators regarding the planktonic communities of Raisali Delvari Dam Lake, 5 stations at its level were selected and sampled. It happened once every 45 days. The NSFWQI index was calculated using 9 parameters of soluble oxygen, fecal total, BOD5, pH, nitrate, phosphate, temperature changes, turbidity and soluble solids. The results of calculating the NSFWQI index showed that the lake did not have suitable conditions in terms of water quality and according to this index, the water quality of the lake was in a moderate position during the study period. Similarly, according to the Iranian Water Quality Index (IRWQI), the water quality of the lake was in poor condition. The Shannon-Wiener Diversity Index also placed the water of the Raisali Delvari Dam Lake on a quality floor with moderate pollution. In general, all the calculated indicators assessed the water quality of the lake as moderate to poor. Based on the results of the water o