Objectives:The present work deals with the study of physico-chemical parameters along with diversity and abundance of zooplanktons to analyse the trophic status of Gopalaswamy tank, Chitradurga, Karnataka, India. Methods: A total of 18 physico-chemical parameters were analysed for a period of two years from July 2019 to June 2021 using EuTech PCS multi-parameter testing probe, secchi disc, hygrometer and titration methods. Zooplanktons were identified and counted under Sedge Wick Rafter counting cell, which holds 01ml of zooplanktons sample spread over one thousand cells. Findings: The water body exhibits low transparency because of the algal bloom and the water is more alkaline with excess nutrient load due to high value of phosphate, sulphate and nitrates. Three groups of zooplanktons comprising 18 species were recorded. Almost 50% of the zooplanktons observed were eutrophic indicators. Cladocera was the species rich group with 09 species, followed by Copepoda having 05 species and Rotifera with 04 species. However, Copepoda was the most abundant group with 993 individuals (47%), followed by Rotifera with 579 individuals and Cladocera with 545 individuals (26%). Out of these 18 species, Diaphanosoma sarsi, Diaphanosoma excisum, Bosmina longirostris, Ceriodaphnia cornuta, Ceriodaphnia reticulata, Simocephalus vetulus, Brachionus falcatus, Brachionus forficula and Lecane ludwigi were indicator species. The variations in the physico-chemical characters, zooplanktons and their inter-relation depict the deterioration of the water body and the need of conservation as the water body harbors eutrophic indicator species. Novelty: The study is the first report on water quality parameters and zooplanktons diversity of the historic and scientifically built water body that never dried though it is situated in arid zone between the rocky terrains. The investigation has revealed the increased nutrient load which supported the abundance of indicator species and responsible for the process of eutrophication. The study suggests that, conservation strategies are essential to revive and protect the https://www.indjst.org/