In Summer, 1974, an intensive field survey was conducted in the Nansemond River estuary from Suffolk to Pig Point. Temporal and spatial distributions of the parameters dissolved oxygen, salinity and temperature were obtained from the survey. Additional slack water runs were conducted in 1974 and 1975. The hydrographic and water quality data, combined with measured bathymetric profiles, were used to construct, calibrate and verify a one-dimensional, time-dependent mathematical model. Modeling of the Nansemond River estuary is part of the continuing program of the Cooperative State Agencies (Virginia State Water Control Board and the Virginia Institute of Marine Science) to develop water quality models of Virginia\u27s estuaries. The Nansemond River is located 14.5 kilometers (9 statute miles) from the mouth of the James River. The river receives industrial and domestic wastes from packing plants, sewage treatment plants, and housing developments. In the river reach around Suffolk, low values of dissolved oxygen (less than 4 mg/1) have been observed. The implicit numerical mathematical model predicts the intra-tidal distribution of dissolved oxygen, biochemical oxygen demand, and salinity. The model accurately predicts the region of low dissolved oxygen