This report presents the results of a study by the U.S. Geological Survey, funded by the Virginia Department of Environmental Quality-Division of Intergovernmental Coordination, to monitor and estimate loads of selected nutrients and suspended solids discharged to Chesapeake Bay from two major tributaries in Virginia. Monitoring was conducted previously from 1984 through 1988. The emphasis was on scheduled monitoring during that period and, therefore, most samples were collected at base-flow conditions. Because some constituent concentrations change during stormflow conditions, and because the increased river discharge affects the total loads of all constituents, the monitoring program was revised in 1988 to include stormflow sampling. The revised sampling scheme, including baseflow and stormflow sampling, increased precision in load estimation. From July 1988 through June 1990, monitoring consisted of collecting depth-integrated, cross-sectional samples from the James and Rappahannock Rivers in Virginia during stormflow and at scheduled intervals, which were sometimes during stormflow but were usually base-flow conditions. Water-quality constituents that were monitored for which loads were estimated included total suspended solids (residue, total at 105 "Celsius), dissolved nitrite-plus-nitrate nitrogen, dissolved ammonia nitrogen, total Kjeldahl nitrogen (ammonia plus organic), total nitrogen, total phosphorus, dissolved orthophosphorus, total organic carbon, and dissolved silica. Other selected constituents also were monitored for which loads were not calculated. Daily mean load estimates of each constituent were computed by month using a seven-parameter loglinear-regression model that used variables of time, discharge, and seasonality. Water-quality data and constituent-load estimates are included in the report in tabular and graphic form. Illustrations of load estimates overlain by hydrographs for the same period, showing the magnitude of the increase in loads that occurs during stormflow events, also are included in the report. Water-quality data are included in tabular form in the appendixes. Wide ranges in estimated loads of constituents were observed for both rivers. Monthly loads of total suspended solids ranged from 257,000 to 339,000,000 kg in the James River and from 22,800 to 184,000,000 kg in the Rappahannock River. Estimated monthly loads of total nitrogen ranged from 72,600 to 1,840,000 kg in the James River and from 3,968 to 750,200 kg in the Rappahannock River. Total phosphorus loads ranged from 35,700 to 469,000 kg in the James River and from 558 to 221,030 kg in the Rappahannock River. The greatest monthly load for all constituents monitored was observed at both rivers in May 1989, when a series of storms resulted in 2 to 3 weeks of above-normal streamflow. During that month, the estimated load of suspended solids was more than 30 percent of the total load for the entire 2-year data-collection period at the James River, and more than 50 percent of the total load for the Rappahannock River.
