Apalachicola River-Quality Assessment The Apalachicola was one of the rivers EXPLANATION 85° Drainage basin of the Chattahoochee, Flint, and Apalachicola Rivers Subbasin boundary ALABAMA GEORGIA River Lake Harding Columbus Walter F. George Lake Chattahoochee River Basin 50 MILES 83° The quality of water in a river is affected by two factors: the unique hydrology of a river basin and man's development and use of the land and the water resources. In the broadest context, the river-quality assessments carried out by the Geological Survey are problem-oriented approaches for obtaining the needed information. The Apalachicola River meanders 106 miles through northwestern Florida to Apalachicola Bay on the Gulf of Mexico. It is a good example of a multiuse waterway system. The area's principal commercial activities, barge traffic, timber harvest, land development, and commercial fishing in the Apalachicola Bay, often require different management practices for optimum returns in this river basin. A flood-plain forest of 175 square miles borders the Apalachicola River in Florida. It has sustained a viable timber industry since the early 1800's. The bottom-land hardwood forest contains over 40 species of trees in a largely undisturbed wetland. This forest was an integral part of the broad interdisciplinary scientific investigation conducted as part of the Geological Survey's assessment. Statistical surveys of tree abundance and distribution were coupled with measurements of leaf production to provide estimates of total production of organic litter in the flood-plain environment. Annual flooding overflows the natural levees and covers the flood plain. In many areas, the water velocities are sufficient to transport the decaying leaf litter into the river and ultimately to Apalachicola Bay. The nutrients and litter material form the basis for one of the most productive estuarine systems in North America. Oysters, shrimp, blue crab, and fish depend on the seasonal materials transported by the floods coming out of the Apalachicola River wetland system. The Apalachicola RiverQuality Assessment developed methods and techniques to quantify the flood-plain contribution to the 1980-81 annual load of nutrients and detritus (organic particulate material) to the bay. Results obtained in the river were compared with estimates of litterfall transported in the flood plain. Such estimates were based on new methods developed during the study. During a 1-year period, approximately 30,000 tons of organic carbon entered the river from the flood plain. This Landsat image, which is a false-color composite obtained on February 11, 1977, shows the extent of the flood plain in the Apalachicola River basin, Florida. The dark color of the flood plain is caused by the low reflectance from flood waters. The 656-footwide river is barely visible in the center of the 2- to 5-mile-wide flood plain. The Apalachicola River flows from Lake Seminole (at the top), 106 miles south, to Apalachicola Bay (near the bottom of the scene). The numerous white squares near the top of the scene are agricultural fields in Florida and Alabama. The large red area east of the river is pine forest (Apalachicola National Forest). The faint brown color on the bird's-foot delta at the river mouth is marsh. The light blue colors near the beaches at the bottom of the scene are a combination of shallow areas and areas with high suspended sediments caused by ocean currents. Research vessel Rockfish. Potomac River Estuary Study Estuaries are potentially the most productive as well as the most fragile and endangered areas of our Nation's coastal environment. Because they are the meeting place of saltwater and freshwater, estuaries are complex hydrodynamic, chemical, and biological environments. The fact that they are sinks for sediments further complicates the picture because nutrients, metals, and organic pollutants are often associated with sediments. These substances may become permanently or temporarily stored in the bottom sediments promoting eutrophication (enrichment of the food supply) and, in the case of metals and organics, sometimes concentrating in the life forms. Partly because of their complexity and partly because it is difficult, dangerous, and expensive to study them, estuarine environments are poorly understood. In light of increasing awareness of their importance and fragility, it becomes more and more imperative to make the extra effort to collect and interpret the data necessary to understand estuarine resources. It was in this vein that, in October 1977, the U.S. Geological Survey began its 5-year Interdisciplinary Potomac Estuary Study. Acceleration of the natural filling process by increased sediment loads from upstream farms and the Washington, D.C., urban area is probably the most visible water-quality problem in the tidal Potomac River and marginal embayments. This process has been so rapid that the Lincoln and Jefferson Memorials now stand on what was described in 1711 as a harbor suitable for great merchant vessels. Another persistent water-quality problem in the tidal river is the depletion of dissolved-oxygen associated with the disposal of municipal sewage and storm runoff from the Washington, D.C., metropolitan area. Following the installation of a water supply system for the District of Columbia in 1859, the problem of effluents and runoff was first apparent when large quantities of domestic sewage began entering the river by way of the storm sewers. Soon the loading was beyond the capacity of the river in the waterfront area of the city, and, by 1899, the river had become so obnoxious that President Benjamin Harrison appointed a board of sanitary engineers to find an outfall location where dilution was adequate and tidal action did not return the sewage to the edge of the city. The development of waterquality problems near the District of Columbia coincided with the growth of population. Improvements in water quality paralleled installation of and improvements in waterpollution-control technology used in the Blue Plains sewage treatment plant, the major treatment facility in the metropolitan area. Some of the worst observed dissolvedoxygen conditions occurred in the mid- to late 1950's when carbonaceous biochemical oxygen demand loadings were at their peak. Today, the major problem has shifted from that of dissolved-oxygen depletion due to carbonaceous biochemical oxygen demand to one of eutrophication caused, at least in part, by the heavy nutrient loadings from the Washington, D.C., area municipal sewage treatment plants. Because 72 percent of the 3.9 million people in the Potomac River basin are concentrated in a metropolitan area and because the primary business is government, the Potomac River, unlike many east coast estuaries and tidal rivers, is relatively free from the pollution problems associated with manufacturing and chemical industries. Therefore, the effects of sedimentation and eutrophication can be studied in the tidal Potomac River and Estuary independent of complications from those of other types of pollutants. The Potomac Estuary Study is one of seven pilot River-Quality Assessments and the only one to concentrate on estuarine problems. Others have concentrated on problems in upland streams such as dissolved oxygen and excessive nutrient enrichment in the Willamette River-Quality Assessment or those associated with energy development and irrigation as in the Yampa Study. The general objectives of the Potomac Study are (1) to conduct research into the physical, chemical, and biological mechanisms governing life cycles of phytoplankton, submerged vegetation, and benthic fauna in tidal rivers and estuaries, (2) to develop mathematical models necessary to support ecological models suitable for predicting the influence of phytoplankton on dissolved oxygen and nutrient levels (these models are designed to expedite water-quality management decisionmaking for the tidal Potomac River and Estuary), and (3) to develop, refine, and standardize efficient techniques for studying water quality of the Potomac and other tidal rivers and estuaries. Examples of some of the many findings of the Potomac Estuary Study are summarized in the paragraphs below. Low-Flow Dissolved-Oxygen Nutrients associated with sediment discharged by the Potomac River during periods of high flow settle to the bottom. They become a major source of dissolved and particulate nutrients in the water column of the freshwater tidal river and estuarine transition zone (see fig. 4 for definition of these zones) during critical periods when river flow is low. During such periods, nutrients released through the 390-million-gallon-per-day discharge from the regional secondary sewage treatment plant cause a dissolved-oxygen sag for approximately 8 nautical miles in the upstream part of the tidal river. In the remainder of the tidal river and in the transition zone, the oxygen regime is dominated by biologic reactions fed by nutrients exchanged with the bottom. During extreme flood events, some of this material is moved to the transition zone. Therefore, the magnitude, frequency, and duration of flood events which transport most of the annual upland nutrient loads may be a major determinant of lowflow water quality in the downstream reaches of the tidal river and transition zone. Tributary Loads A sampling program was begun in 1979 to acquire data on monthly and major-storm Percentage of material supplied during 1980 and 1981 water years and trapped in the various zones of the tidal Potomac River and Estuary. [Negative numbers in parentheses indicate a net outflow of dissolved silica from the transition zone. This is included in the material trapped in the estuary and is, therefore, not subtracted from the total percentage. The percentage of material supplied to the Chesapeake Bay is 100 minus the number shown on the line labeled "Total percentage" ] |