Benthic algae play a significant role in food webs and also used for observing long term trends in community changes that can occur because of nonpoint source of pollution. Diatoms which occur in large numbers and are well preserved due to the presence of frustules Their distinctive characteristic feature is the possession of siliceous cell walls, used to define and classify species conformity. Since silica resists against degradation, diatoms are well preserved in fresh water as well as marine sediments. The persistence of diatom frustules in the reservoir environment enables prehistoric conditions to be constructed based on the narrow ecological preferences of most species. The present study reveals the distribution and abundance of diatom community of Krishnagiri reservoir utilize for agricultural purposes along with domestic needs. Surface water and sediment samples were collected through PVC pipe and the sediment samples were sliced into 3 sections with the 5 cm intervals. Each section was sieved into 2 fractions using 50 µm and 120 µm sieve. Water quality parameters were also analyzed using standard methods. Sediment diatom samples were preserved in 4% formalin. Specimens were identified with the help of authentic literature. Totally 24 diatom species were identified. Morphometric measurements were taken. Abundance and distribution of sediment diatoms at different locations of Krishnagiri reservoir were estimated. Our data provide valuable information about the distribution and abundance of diatoms present in KRP dam. The regulation of the inflow and outflow of this dam influences various physicochemical variables in turn shaping the diatom community structure.