Water quality monitoring is one of the important function of State Pollution Control Board. It helps in evaluating the nature & extent of water contamination, assess the water quality trends, evaluate the success of pollution control measures taken & prioritization of efforts to be initiated. Maharashtra Pollution Control Board is monitoring water quality under National Water Monitoring Programme (NWMP) and State Water Monitoring Programme (SWMP) at various locations as per the Uniform Monitoring Protocol of CPCB/MoEF, New Delhi. This document contains compilation and statistical analysis of Water Quality Monitoring data observed at 250 monitoring stations during the period 2011 to 2012.