Pahuj Reservoir, situated at north east part of district Jhansi, is the sole source of drinking water for the local people. The geochemical water quality of the reservoir was found under the influence of seasonal variation due to phosphate carbonate rock weathering and atmospheric precipitation. Hence, a detailed and systematic study was carried out to assess the concentration of major ions like HCO3-, Cl-, SO42-, PO43-, NO3-, Ca2+, Mg2+, Na+ and K+ in reservoir for pre-monsoon, monsoon and post-monsoon in 2010. Through the statistical analysis it was observed that concentration of major ions in reservoir was found higher in pre-monsoon followed by post-monsoon and monsoon.