Sediment-water column exchanges of nutrients and oxygen in the tidal James and Appomattox Rivers

Fluxes between the sediments and overlying water of ammonium, nitrate, total phosphorus, ortho phosphorus, and dissolved oxygen have been measured in the tidal James and Appomattox Rivers, Va. A total of 68 nutrient flux measures, 203 oxygen flux measures, and 18 control measures were collected in the summer months, 1983 and 1984. Ammonium is predominantly released from the sediments at a mean rate of 9.82 mg/m /hr. Nitrate is predominantly taken up by the sediments at a mean rate of 1.53 mg/m /hr. Total phosphorus is taken up by the sediments at a mean rate of 1.67 mg/m /hr. Ortho phosphorus may be taken up or released. Mean flux is an uptake of 0.75 mg/m /hr. Dissolved oxygen is taken up at a mean rate of 44 mg/m /hr. The primary implication of this st udy for management is that the occurrence and rate of nitrification in the water column are obscured by the simultaneous sediment release of ammonium and uptake of nitrate. It is recommended that nitrification rates in an existing water-quality model of the James River be recalibrated following inclusion of the benthic nitrogen fluxes

Two-dimensional, intratidal model study of salinity intrusion structure and motion in partially-mixed estuaries (Virginia)

A two-dimensional, longitudinal-vertical model for partially-mixed estuaries has been developed. The model provides intratidal predictions of surface level, velocity, and salinity through a semi-implicit finite-difference solution to the continuity and momentum equations and an explicit finite-difference solution to the salinity equation. The model was verified through comparison with analytical solutions, laboratory data, and prototype data. Following verification, the model was used to simulate the destratification-stratification cycle which occurs in the James River Estuary, Virginia, coincident with the spring-neap tidal cycle. In a second application to the James, a simulation of the movement of the salinity intrusion following a storm-generated freshwater flow pulse was conducted. Investigations were conducted into the reaction of a hypothetical estuary to step-like and pulse-like alterations in wind stress, tide range, boundary conditions and flow. It was noted that the reaction time-scale of the estuary was much longer than the time-scale of alterations in the forcing functions. Thus, in prototype estuaries in which forcing functions are periodic and/or randomly superimposed, truly steady-state conditions are never attained

Sediment oxygen demand in Hunting Creek and the Potomac River

Sediment oxygen demand measures were conducted in Hunting Creek during the period June 17 to August 19, 1986

Water Quality in a Small Tidal Creek: Parker Creek, Virginia

Parker Creek is a branched tidal creek located on the Eastern Shore of Virginia. In its southern branch, the creek receives waste inputs from a poultry processing plant. A study has been conducted to determine the effects of these inputs and to formulate a mathematical model of the creek system suitable for water quality planning. The model and field studies show the creek may be divided into two zones, an upstream zone dominated by freshwater flows and waste inputs, and a downstream zone dominated by conditions in adjacent Metomkin Bay. In the upstream zone of the waste-receiving branch, conditions of elevated nutrient and depressed dissolved oxygen concentrations exist. In the downstream zone, conditions are close to natural. For purposes of comparison, surveys were conducted in three similar non-impacted tidal creeks and in Metornkin Bay. From a planning standpoint, the most significant result of these surveys is that violations of minimum dissolved oxygen standards may occur as a natural condition in tidal creeks

Influence of Reservoir Infill on Coastal Deep Water Hypoxia

Ecological restoration of the Chesapeake through the Chesapeake Bay total maximum daily load (TMDL) requires the reduction of nitrogen, phosphorus, and sediment loads in the Chesapeake watershed because of the tidal water quality impairments and damage to living resources they cause. Within the Chesapeake watershed, the Conowingo Reservoir has been filling in with sediment for almost a century and is now in a state of near‐full capacity called dynamic equilibrium. The development of the Chesapeake TMDL in 2010 was with the assumption that the Conowingo Reservoir was still effectively trapping sediment and nutrients. This is now known not to be the case. In a TMDL, pollutant loads beyond the TMDL allocation, which are brought about by growth or other conditions, must be offset. Using the analysis tools of the Chesapeake TMDL for assessing the degree of water quality standard attainment, the estimated nutrient and sediment loads from a simulated dynamic equilibrium infill condition of the Conowingo Reservoir were determined. The influence on Chesapeake water quality by a large storm and scour event of January 1996 on the Susquehanna River was estimated, and the same storm and scour events were also evaluated in the more critical living resource period of June. An analysis was also made on the estimated influence of more moderate high flow events. The infill of the Conowingo reservoir had estimated impairments of water quality, primarily on deep‐water and deep‐channel dissolved oxygen, because of increased discharge and transport of organic and particulate inorganic nutrients from the Conowingo Reservoir