Physical and chemical water-quality data and nitrogen and phosphorus yields for 29 sites sampled in two synoptic surveys of streams within the Lewisville Lake watershed are presented in this report. The two synoptic surveys were conducted in March 1984 and March 1985, as a reconnaissance and assessment of water quality and nitrogen and phosphorus yields throughout the watershed. This work was cooperatively funded by the city of Dallas and the U.S. Geological Survey (USGS) as part of a hydrologic study to quantify nonpoint nutrient loads to Lewisville Lake.