The Virginia Mainstem Monitoring Program is conducted by ODU and consists of 27 sites located from the mouth of the Chesapeake Bay to the Eastern Shore’s Pocomoke Sound.

The objectives of the Mainstem Water Quality Monitoring Program are:

• To determine if water quality conditions satisfy the requirements necessary to protect living resources from nutrient and sediment impacts,
• To diagnose the likely causes of non-attainment and assess progress toward improvements still needed, and
• To support continued refinement, calibration and validation of the Chesapeake Bay Water Quality Model and multi-species management models.

Sampling occurs monthly throughout the year except in June and August, when sampling occurs twice monthly. Whenever possible, sampling is coordinated with the Maryland mainstem monitoring schedule to provide a synoptic picture of the Bay.

Physical measurements (temperature, pH, salinity, specific conductance and dissolved oxygen) are obtained by probe every meter to a depth of 15 meters, then every 2 meters to a depth of 1 meter above the bottom and light penetration measurements are made via Secchi Disk and Incident Radiation. Chemical parameters are obtained from surface and bottom at all sites and from above and below the pycnocline at a few select sites. Chemical parameters at each site consist of: Silicate (filtered), Particulate Carbon, Total Suspended Solids, Chlorophyll a and Phaeophytin, Particulate Nitrogen, Dissolved Persulfate Nitrogen, Nitrate + Nitrite (filtered), Nitrite (filtered), Ammonia (filtered), Particulate Phosphorus, Dissolved Phosphorus and Dissolved Orthophosphate.

At each station, a vertical profile of in vivo fluorescence (IVF) is also collected. IVF readings are taken at 1 meter, 2 meter, and 3 meter, and at 3 meter intervals thereafter to 1 meter above the bottom. As appropriate, water from the discharge hose of the fluorometer will be collected for calibration purposes. Vertical profiling will be conducted only when the vessel used is capable of performing vertical profiles.

This program is currently completed by DEQ. Water quality conditions are monitored at 32 stations in major tributaries to the Bay Mainstem and 12 stations on the Elizabeth River.

The objectives of the Tributary Water Quality Monitoring Program are:

• To determine if water quality conditions meet requirements necessary to protect living resources from nutrient and sediment impacts
• To diagnose the likely causes of non-attainment and assess progress toward improvements still needed
• To support continued refinement, calibration and validation of the Chesapeake Bay Water Quality Model and multi-species management models. The program also provides information necessary to measure effectiveness of point and non-point source programs in reducing nutrient input to the Bay.

All stations are sampled once each month. Sampling is coordinated by the regional offices to attempt to sample entire tributaries on the same day. Weather permitting, sampling occurs on consecutive Tuesdays with the James River run conducted on the first Tuesday of the month, followed by the Rappahannock (Piedmont and Northern Virginia regional offices) and Elizabeth Rivers (DEQ Tidewater Regional Office) and then the York River.

The field measurements obtained include the following:

1. Secchi disk.
2. A vertical profile of temperature, dissolved oxygen, pH, specific conductance and salinity. The vertical profile starts at 1 meter above the bottom sediment (depth rounded to the nearest whole meter) and continues at 1-meter intervals toward the surface.

Light Attenuation: An initial underwater light reading is just below the surface (approximately 0.1 meter) and with the deck sensor. Subsequent readings are taken in 0.5-meter increments. Rough sea conditions, strong tidal currents and light reflection off the side of the boat adversely affect the determination of precise depths. As such, when conditions have become too rough, light attenuation measurements are not recorded.

Chemical parameters are obtained from surface and bottom at all sites. Chemical parameters at each site consist of: Silicate (filtered), Particulate Carbon, Total Suspended Solids, Chlorophyll a and Phaeophytin, Particulate Nitrogen, Dissolved Persulfate Nitrogen, Nitrate + Nitrite (filtered), Nitrite (filtered), Ammonia (filtered), Particulate Phosphorus, Dissolved Phosphorus, and Dissolved Orthophosphate.

The River Input Monitoring Program (RIM) was initiated in Virginia in 1988 to characterize the status and trends of nutrients and sediment loads to the Bay from the non-tidal watersheds of the major Bay tributaries. The program initially consisted of routine, monthly monitoring and storm events at one site at each of the Fall Lines of the James, Rappahannock, Appomattox, Mattaponi and Pamunkey rivers. Since that time, the non-tidal monitoring program has been expanded to include sites beyond just the fall-line stations in the North and South Forks of the Shenandoah River, the North Anna River, the Chickahominy River, the Rapidan River, the Smith River and the Rivanna River. In 2012, USGS began targeted storm sampling at sites already monitored routinely on the Appomattox, Rappahannock and Mattaponi rivers and implemented a new site for routine and storm sampling on Polecat Creek for a total of 36 sites in Virginia.

Site selection for the non-tidal network are based on:

1. Location to the outlet of rivers draining the Tributary Strategy Basin
2. Locations delivering the largest amounts of nutrients and sediment to the Chesapeake Bay or its tributaries
3. Importance to watershed modeling efforts for closing areas of large data gaps, such as in the area of the Coastal Plain.

The frequency of data collection is as follows:

Discharge: At each monitoring station, a stream gage is maintained to provide a record of daily stream flow. Although continuous stream flow is usually available, the minimum data requirement is a daily time-step.

Routine water-quality monitoring: Monthly water quality samples are to be collected from all sites. Storm Samples: A minimum of eight water-quality samples also will be collected during storm events at each site; the eight storm samples will be collected during no fewer than four independent storm flow periods.

Continuous Monitors:  The in-situ continuous water-quality monitors will be serviced approximately monthly to clean the instruments and check calibration. Additional servicing of the continuous monitors will be performed as needed due to instrument fouling and malfunctioning.

Field parameters are collected at all sites and include water temperature, air temperature, barometric pressure, dissolved oxygen, specific conductance, pH and turbidity. (Note: DEQ does not collect Barometric Pressure or Turbidity field measurements, but is reviewing the resource needs for possibly including these measurements in the future).

The Virginia Division of Consolidated Laboratory Services (DCLS) analyzes each composite water sample for several parameters at six sites on the James, Appomattox, Mattaponi, Pamunkey and Rappahannock River sites. The parameters include Total Dissolved Nitrogen, Particulate Phosphorus, Total Dissolved Phosphorus, Total Suspended Solids, Dissolved Nitrite, Fixed Suspended Solids, Dissolved Ammonia, Sand/Silt/Clay (quarterly samples only), Dissolved Nitrate, Volatile Suspended Solids, Total Phosphorus, Dissolved Orthophosphate, Particulate Inorganic Carbon, Particulate Inorganic Phosphorus, Dissolved Silica, Dissolved Organic Carbon, Particulate Carbon, Chlorophyll and Phaeophytin, Particulate Nitrogen, and Suspended Sediment (analyzed at USGS sediment Lab in Kentucky).

DCLS analyzes each composite water sample for the following parameters at all remaining sites: Total Nitrogen, Total Suspended Solids, Total Phosphorus, Total Suspended Sediment, Total Nitrite plus Nitrate, Dissolved Orthophosphate and Total Ammonia.

USGS utilizes these data to run status and trends through a Weighted Regression on Time, Discharge, and Season as developed by Hirsch et al. and Moyer et al.¹ Since its inception, time the non-tidal monitoring program has been expanded to a total of 36 sites in Virginia.

^[1] Hirsh, R.M., Moyer, D.L., and Archfield, S.A., 2010, Weighted regression on time, discharge, and season; and,  Moyer, D.L. Hirsh, R.M. and Hyer, K.E. 2012, Comparison of two regression-based approaches for determining nutrient and sediment fluxes and trends in the Chesapeake Bay watershed: U.S. Geological Survey Scientific Investigations Report 2012-5233, 118p.

The near shore monitoring component was initiated as a cooperative agreement with VIMS in 2003 and consists of the deployment of continuous monitoring devices and data flow cruises that track throughout a select tributary or Bay segment in the polyhaline, oligohaline and mesohaline portions of Virginia’s Chesapeake Bay tributaries or segments of the mainstem from April through September of each year. The program was designed to rotate through Virginia’s major tributaries and Bay mainstem segments on a three year basis. The York and James systems were sampled 2006 - 2008, the Rappahannock and Potomac systems 2007 - 2009, the upper mainstem segments 2010-2015, the polyhaline segments of the Eastern Shore and tributaries 2016-2018, and the Lynnhaven River, Thalia Creek and the lower Chesapeake Bay polyhaline segment CB8PH were sampled in 2019- 2021.

All data collected for the Virginia Shallow Water Monitoring Program may be found on the VIMS Virginia Estuarine and Coastal Observing website: http://vecos.vims.edu/.

Some aspects of continuous monitoring and dataflow are conducted through other non-CBP efforts (e.g., by Hampton Roads Sanitation District and National Estuarine Research Reserve) not described here. The data generated by these efforts is also available on the VECOS website and used by DEQ for assessment when available.

The Mainstem Monitoring also contains a living resource component that monitors phytoplankton and benthic organisms, conducted by Old Dominion University. Currently, Virginia only assesses the benthic component of the living resource program. Benthic organisms are important secondary producers, providing key linkages between primary producers (phytoplankton) and higher trophic levels (crabs, bottom-feeding fish and water birds).

Benthic invertebrates are among the most important components of estuarine ecosystems, and may represent the largest standing stock of organic carbon in the Chesapeake Bay. Some benthic organisms, such as hard clams and soft-shell clams, are economically important. Others, such as polychaete worms and shrimp-like crustaceans, contribute significantly to the diets of economically important blue crabs and bottom-feeding juvenile and adult fish such as spot, croaker, striped bass and white perch. In Virginia, 21 fixed‑point stations are sampled for benthos one time per year (September) and 100 probabilistic sites are sampled once per year over the course of the summer.

The objectives of the Chesapeake Bay Estuarine Benthic Macroinvertebrate Monitoring Program are:

1. To characterize the health of regional areas of the lower Chesapeake Bay as indicated by the structure of the benthic community.
2. To conduct trend analyses on long‑term data, at fixed‑point stations, to relate temporal trends in the benthic communities to changes in water and/or sediment quality. The trend analyses will be updated annually as new data are available.
3. To warn of environmental degradation by producing a historical data base that will allow annual evaluations of biotic impacts by comparing trends in status within probability-based strata and trends at fixed‑point stations to changes in water and/or sediment quality.