Statistical analyses were conducted for six water-quality constituents measured at 371 surface-water-quality stations during water years 1998-2009 to determine changes in concentrations over time. This study examined year-round concentrations of total dissolved solids, dissolved nitrite plus nitrate, dissolved phosphorus, total phosphorus, and total nitrogen; concentrations of dissolved chloride were measured only from January to March. All the water-quality data ana-lyzed were collected by the New Jersey Department of Envi-ronmental Protection and the U.S. Geological Survey as part of the cooperative Ambient Surface-Water-Quality Monitoring Network.