Zooplankton is a microscopic organism that forms the basis of food chains and food networks in all aquatic ecosystems. All secondary production in aquatic ecosystems is based directly or indirectly on plankton. They also play an essential role in recycling nutrients and energy in their respective environments. They located in the pelagic area of ponds, lakes, rivers and oceans, where light enters. Plankton releases large amounts of organic matter, which dissolve and integrate into the biomass of various bacteria. Zooplankton is an essential food for omnivores and carnivore fish. In the present study, seasonal fluctuations, correlation coefficients were established from Harsool dam in Aurangabad, India. A total of 25 zooplankton species were recorded, belonging to the orders Cladocera (8 species), Copepoda (5 species), Rotifera (10 species), and Ostracoda (2 species). The present study found that a total of 19220 (organisms/liter) zooplankton noticed in Harsool dam in summer 8120 (organisms/liter), in monsoon 6310 (organisms/liter) and winter 4790 (organisms/liter) that constituted 29.76% of Cladocera, 30.28% of Copepoda, 37.04% of Rotifera and 2.91% Ostracoda were recorded during the current study period. The study showed that the most critical factors for the growth of zooplankton are calcium and free CO₂. A high value of biodiversity, in summer, shows a longer food chain than other seasons. According to the Shannon index, the values show that the waters of the Harsool dam are contaminated. Evenness indices indicate whether all species are equally common in a sample.