Historical water quality data from about 100 sampling stations on streams, canals and lakes in central and southern Florida were analyzed for areal and temporal variations in water quality, statistical measures of the data, relationships between water quality variables, and long term changes or trends in water quality. Included in the analysis were data on the major inorganic chemical constituents, temperature, nitrogen and phosphorus species, trace metals, pesticides, organic carbon and biochemical oxygen demand. Based on the results of the analysis, a network was designed which would provide data to meet six specific objectives: (1) water quality accounting, (2) areal assessments (3) detection of gross long-term trends, (4) detection of toxic and deleterious substances, (5) establish a limnological data base on lakes and (6) furnish data on chemical inputs from the atmosphere.