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Research about Potomac River

Source-linked reports with geographic coverage including Potomac River.

28 records · Page 2Linked to original sources
USGS1986

Effect of discharge on the chlorophyll a distribution in the tidally-influenced Potomac River

In the tidal Potomac River, high river discharges during the spring are associated with high chlorophyll a concentrations in the following in the following summer, assuming that summertime light and temperature conditions are favorable. Spring floods deliver large loads of particulate N and P to the tidal river. This particulate N and P could be mineralized by bacteria to inorganic N and P and released to the water column where it is available for phytoplankton use during summertime. However, during the study period relatively low concentrations of chlorophyll a (less than 50 μg l −1 occurred in the tidal river if average monthly discharge during July or August exceeded 200 m 3 s −1 . Discharge and other conditions combined to produce conditions favorable for nuisance levels of chlorophyll a (greater than 100 μg l −1 approximately one year out of four. Chlorophyll a maxima occurred in the Potomac River transition zone and estuary during late winter (dinoflagellates) and spring (diatoms). Typical seasonal peak concentrations were achieved at discharges as high as 970 m 3 s −1 , but sustained discharges greater than 1,100 m 3 s −1 retarded development. Optimum growth conditions occurred following runoff events of 10 to 15 d duration which produced transit times to the transition zone of 7 to 10 d. Wet years with numerous moderate-sized runoff events, such as 1980, tend to produce greater biomass in the transition zone and estuary than do dry years such as 1981.

Potomac River↗
USGS1985

The effects of grazers and light penetration on the survival of transplants of Vallisneria americana Michs in the tidal Potomac River, Maryland

Poor light penetration and grazing are among the factors potentially responsible for the lack of submersed aquatic macrophytes in the tidal Potomac River. Between 1980 and 1983, plugs, springs and tubers of Vallisneria americana Michx were transplanted from the oligohaline Potomac Estuary to six sites in the freshwater tidal Potomac River. Transplants made in 1980 and 1981 were generally successful only when protected by full exclosures which prevented grazing. Grazing resulted in the removal of whole plants or clipping off of plant leaves in unprotected plots. Plants protected in the first year were permanently established, despite the occurrence of grazing in subsequent years, at Elodea Cove and Rosier Bluff, where light penetration was high (average 1% light level was 1.6–1.7 m). Plants were not permanent;y established at Goose Island, where light penetration was lower (average 1% light level was 1.4 m) and grazing occurred, or Neabsco Bay where light penetration was very low (average 1% light level was 1.0 m) and grazing may not have occurred. In 1983, Secchi depth transparencies in the upper tidal river were improved significantly compared to 1978–1981. Both protected and unprotected transplants thrived in 1983.

Maryland↗
USGS1985

Controls on phosphorus mobility in the Potomac River near the Blue Plains wastewater treatment plant

The Blue Plains wastewater treatment plant is the largest point source of phosphorus in the Potomac River basin, discharging an average of 2 metric tons of phosphorus into the river each day in 1980. An intensive study of the water and sediments in the vicinity of the treatment plant was conducted in 1979-80 in order to characterize the major factors controlling the mobility of effluent-derived phosphorus in the area. The transport of phosphorus near the treatment plant was found to be affected by the circulation regime, by inorganic adsorption reactions with sediments, and by metabolic uptake and release by phytoplankton. The effect of river discharge on the convective transport of phosphorus near the outfall is significantly reduced by a mid-river shoal area, which confines the flow path of the effluent to an embayment on the eastern side of the river for a distance of 4 kilometers below the outfall. This embayment appears to serve as a sediment trap, where protection from bottom scour during high-flow events has permitted fine-grained sediments to accumulate. Measurements of mean residence time indicate that the effluent leaves the embayment area 21? days after being discharged from the outfall. Measurements of the linear decay constant for the removal of dissolved phosphorus from the water column reveal a diurnal cycle corresponding to the metabolic utilization of phosphorus by phytoplankton. This cyclic removal is superimposed on a constant and noncyclic adsorption of phosphorus by inorganic phases. Forty-eight hour average values of the linear decay constant for dissolved phosphorus in the area range from 0.4 to 1.1 per day. Analyses of bottom sediments indicate that approximately 13 percent of the phosphorus discharged between September 1977 and August 1980 has been retained in the embayment. The primary inorganic phase responsible for phosphorus adsorption is amorphous iron (ferric oxy-hydroxides); amorphous aluminum and clay minerals appear to play secondary roles. The accumulation of sorbed phosphorus in the embayment has been promoted by the deposition of fine-grained sediments enriched in ferric oxy-hydroxides. Conversely, the absence of ferric oxy-hydroxides in coarse-grained sediments near the outfall has facilitated the precipitation of the ferrous phosphate mineral vivianite.

District of Columbia, Maryland, Virginia↗
USGS1982

Downstream effects of reservoir releases to the Potomac River from Luke, Maryland, to Washington, D.C.

A digital computer flow-routing model was developed for the Potomac River in order to determine the downstream effects of flow releases from the Bloomington and Savage River Reservoirs. Both reservoirs are located above Luke, Maryland approximately 230 miles upstream from Washington, D. C. The downstream effects of reservoir releases were determined by using the unit-response method of flow routing implemented by a diffusion analogy. Results are in the form of unit response coefficients which are used to route flows downstream from Luke. A 24-hour sustained reservoir release input at Luke will result in 35 percent of the flow arriving at Washington, D.C., during the 4th day after the beginning of the release, followed by 61 percent and 4 percent arriving on the 5th and 6th days, respectively. For a 7-day sustained reservoir release, 47 percent of the flow will arrive during the 1st week, and 53 percent will arrive the 2d week. Two methods were used to estimate the amount of water that goes into channel storage between Luke and Washington, D.C., during sustained reservoir releases. Analysis of the flow-routing results indicates channel storage is equivalent to the volume of water releases over a 3.7-day period. Using channel geometry relationships, that volume is equal to 3.2 days ' release. (USGS)

Maryland, Washington D.C.↗
USGS1980

Physical and chemical properties of the Potomac River and environs, April-May 1978

Basic data on the physical and chemical properties measured over the period 24 April through 4 May 1978 on the tidally influenced Potomac River and estuary are presented herein. One 28-hour time series, 45 vertical profiles, and approximately 170 surface observations were made of the distributions of salinity, temperature, light transmission, chlorophyll-a fluorescence, dissolved oxygen, partial pressure of CO2, orthophosphate, nitrate+nitrite, nitrite, ammonia, and silicate. Additional analyses were performed on discrete samples collected for particulate organic carbon, alkalinity, pH, suspended particulate matter, total phosphate, total nitrogen, total dissolved phosphate, and total dissolved nitrogen.

Maryland, Virginia, West Virginia↗
USGS1980

Physical and chemical properties of the Potomac River and environs, August 1978

Basic data on the physical and chemical properties measured over the period 21 August through 31 August 1978 on the tidally influenced Potomac River and estuary are presented herein. Forty-two vertical profiles, and approximately 170 surface observations were made of the distributions of salinity, temperature, light transmission, chlorophyll-a fluorescence, dissolved oxygen, partial pressure of CO2, orthophosphate, nitrate+nitrite, nitrite, ammonia, and silicate. Additional analyses were performed on discrete samples collected for particulate organic carbon, alkalinity, pH, suspended particulate matter, total phosphate, total nitrogen, total dissolved phosphate, and total dissolved nitrogen.

Maryland, Virginia, West Virginia↗
USGS1976

Relations among surficial materials, light intensity, and sycamore-seed germination along the Potomac River near Washington, D.C.

Seed of sycamore, a common tree on river flood plains, germinate in mineral soil exposed to high light intensities. Germination rates are low on surfaces covered with leaf litter, and seedlings die when shaded by closely spaced herbaceous plants. All germination rates were higher when seed were kept moist. Surflcial materials and light values in this study are similar to those on flood plains. Results were derived from counting seedlings after planting 1,000 seeds in each of several flats filled with different kinds of flood-plain and upland soils.

District of Columbia, Virginia↗
USGS1942

Observations on the natural and artificial propagation of the smallmouth black bass, Micropterus dolomieu

Counts of smallmouth black bass nests in the same sections of the South Branch of the Potomac, the Cacapon, and the Shenandoah Rivers are reported over a period of several seasons. The 4‐year record for the South Branch of the Potomac indicates little change in the smallmouth black bass population. The number of nests varied between 50.7 and 73.2 and averaged 58.1 for each mile of stream. The results of fry counts from wild nests showed an average of 2,159 fry in each nest in the South Branch of the Potomac, 2,210 in the Cacapon River, and 1,998 in the Shenandoah River. One important characteristic of natural propagation in these rivers is the simultaneous occurrence of spawning in any section of stream having similar conditions. Evidence is supplied to support the theory that a long, drawn‐out spawning season in artificial ponds is due to annoyance of the brood fish. The importance of attendance by the male fish at the nest is pointed out. Examples in pond culture are given to demonstrate that there are other factors involved in the spawning of smallmouth black bass besides temperature. These factors are annoyance, over‐crowding of the brood fish, and lack of provision for greater individual privacy among the brood bass during their spawning season. In general, productivity of fry apparently increases with age and size of the brood fish.

Maryland↗