STATISTICAL CHARACTERISTICS OF SURFACE WATER QUALITY IN EASTERN MASSACHUSETTS

The USGS National Water-Quality Assessment (NAWQA) Program provides long-term measurements on streams, rivers, ground water, and aquatic systems. Using data from Eastern Massachusetts streams, we present a characterization of current state of surface water, changes in time and dependence on land use, precipitation regime, and possible other natural and human influences. Time series analysis is used to detect changes and relationship with discharge and precipitation regime. Bivariate and multivariate statistics are employed to analyze relationships among multiple chemical variable monitored. The principal component analysis provides a description of data and interpretation of observed variability due to the main influences. About 80 % of the total variance in data is explained by three principal components. Geographic Information Systems (GIS) tools are applied to assess the land use and distinguish urban and rural influences. A combination of GIS and statistical analysis can provide a valuable framework to address complex hydrological systems, and the problem of water quality management based on data sampled during NAWQA. Particularly the increase in salt concentration in groundwater and surface waters, with impact on drinking water quality is illustrated. Notably, salt concentration increase in water can be linked to road salt usage during winters with heavy snowfall and other factors. The maximum Chloride concentration varied between 8.4 mg/L in Kennebec River and 673 mg/L in Aberjona River. Natural factors can also cause higher salt concentration values in rivers. Drought conditions can increase the salt concentrations in a waterbody in two ways: (a) drought can cause inflowing waters to have higher salt concentrations, and (b) heat and low humidity can increase the rate of evaporation in open water, leaving the waterbody with a higher concentration of salt.