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Seven Texas estuarine areas are described in terms of their dimensions; major vegetation types; geology and geological history; drainage basins and stream discharge records; hydrological, biological, and benthic properties; populations and economic development; pollution; and navigation projects. These areas include the Sabine Lake, Galveston Bay, Matagorda Bay-Brazos River Delta, San Antonio Bay, Copano-Aransas Bay, Corpus Christi Bay, and the Laguna Madre. A list of pertinent literature is also presented. The estuaries cover over 1,532,000 acres (620,460 hectares) of open waters and are surrounded by an additional 1,141,400 acres (462,267 hectares) of marshlands and tidal flats. They are formed from either drowned river mouths or the development of barrier islands and peninsulas, and are late Pleistocene and Recent in age. Approximately three-fourths of the more than 39,000 cubic feet per second entering these waters from gaged streams enters Sabine Lake and Galveston Bay. Water temperatures are generally lower on the upper coast than the lower coast during the winter but are relatively uniform during the summer. Salinities generaUy range from about 5 to 25%o except in the Laguna Madre area where hypersalinity is common. A rich and varied fauna displaying many varied life-history types is supported by these waters. Human populations in Cameron Parish, La. and Texas counties contiguous to the seven estuarine areas increased from 31,751 persons in 1850 to 2,962,125 persons in 1970. A sharp increase resulted when oil production began in 1901, and an economy based on manufacture of petrochemicals, shipping, and other industries expanded. Beef cattle and cotton are the mainstays of Texas coastal agriculture, with rice important on the upper coast while citrus fruits are important to the economy of the lower Laguna Madre area. The Texas coast is also important for its sport and commercial fisheries and for waterfowl hunting. Pollution from domestic and indsutrial sources has forced the closing of about 325,090 acres (131,661 hectares) of open bay waters to shellfishing and an adflitional 16,600 acres (6,723 hectares) closed on a conditional basis. Over 1,050 miles (1,691 km) of Federal navigation channels are situated on the Texas coast, the most important of which is the Gulf Intracoastal Waterway, which extends from the Sabine River to Brownsville. Large areas of open estuarine waters, especially in the Sabine Lake and Galveston Bay areas, have been displaced by large spoil areas. INTRODUCTION There has been a growing need for documentation and classification of the physical and biological characteristics of coastal waters throughout the Gulf of Mexico. Demands upon water resources of Gulf coast estuaries and associated watersheds are producing rapid and marked changes in the estuarine evironment. Increased use of freshwater, much of it for human consumption, is hastening construction of dams and diversion channels, and this reduces flow to Gulf estuaries. Construction of channels and placement of spoil, activities associated with exploitation of mineral resources, and construction for waterborne commercial and recreational facilities are altering water circulation and interchange patterns in the estuaries. Flood control and hurricane protection structures also modify estuarine conditions. Effects of such modifications upon estuarine flora and fauna are noticeable, but these effects have not been cataloged for the northern Gulf. Preparation of reports that evaluate proposed water resource projects is often laborious and time-consuming because background information on coastal areas is not easily available. The Cooperative Gulf of Mexico Estuarine Inventory and Study was designed to provide background information on coastal waters of the states bordering the Gulf. 'Gulf Coastal Fisheries Center, Galveston Laboratory, NMFS, NOAA, Galveston. TX 77550. The planning and organizing of the format were done under the auspices of the Estuarine Technical Coordinating Committee (ETCC) of the Gulf States Marine Fisheries Commission, composed of representatives of the fishing industry and of the State and Federal conservation agencies in Alabama, Florida, Louisiana, Mississippi, and Texas. Partial funding for the study in Alabama, Louisiana, and Mississippi was provided through the Commercial Fisheries Research and Development Act (Public Law 88-309, as amended). The Galveston and St. Petersburg Beach Laboratories of the Gulf Coastal Fisheries Center, National Marine Fisheries Service, NOAA, undertook the Texas and Florida portions of the study largely because other uses were made of Public Law 88-309 funds in those states. Members of the ETCC developed work outlines that all participants agreed to follow so that methods of study would be similar and the results comparable. The material presented here uses the format of the Area Description portion of the report. THE TEXAS COAST The Texas coastline is nearly 370 miles (595 km) long. Climate of coastal Texas ranges from humid in the Sabine Lake area (Port Arthur), where the average annual precipitation exceeds 55 inches (1,397 mm), to semiarid in the Rio Grande Delta (Port Isabel), where annual rainfall slightly exceeds 25 inches (635 mm) (Table V. Temperature likewise exhibits considerable variation along the Texas coast. Port Isabel's average January temperature of 62.2°F a6.7°C) contrasts with the 53.6°F U2.0°C) recorded for the Port Arthur and Houston airports (Table 2). Average rainfall ranges from less than 30 inches l762 mm) in the Rio Grand Delta to over 55 inches (1,397 mm) in the Sabine Lake area. The growing season is usually more than 300 days. Tidal marshes and mud flats border all of the estuaries which, with the exception of the Laguna Madre, are too turbid to support extensive growths of submerged vegetation. The dense salt marshes typical of the humid estuaries of the upper Texas coast are gradually replaced on middle and lower coasts with mud flats and with small marsh plants that tolerate high salinity. Texas estuaries have two basic shapes: 1) simple (oval) and 2) complex (branching or dendritic). All are in the second category except Sabine Lake (Figs. 1-3). Geomorphologically, Texas estuaries are of two types: 1) coastal plain, composed of drowned river mouths, and 2) bar-built, in which an offshore sand bar partially encloses a body of water (Pritchard 1967). The first type is represented by Sabine Lake, Galveston and Trinity bays, Matagorda and Lavaca bays, San Antonio Bay, Copano Bay, Corpus Christi Bay, and Baffin Bay. Estuaries of the Brazos and Colorado rivers and of the Rio Grande have filled. Examples of the second type include East and West (Galveston) bays, eastern Matagorda and East Matagorda bays, Espiritu Santo Bay, Aransas and Redfish bays, and the Laguna Madre. Most Texas estuaries have relatively shallow depths that permit mixing of surface and bottom waters through the action of wind-driven waves and normal flow of tidal currents, thus they were considered to be one-layer systems. Emery and Stevenson (1957) define two types of estuaries based upon tidal and salinity features: 1) normal or "positive" type, and 2) hypersaline or "negative" type. The former is characterized by having upstream salinities lowered by adequate river discharge -and mixing; the latter, found in arid regions, is characterized by poor land runoff, limited tidal influence, and salinities higher than those of the adjacent ocean. The bays of Texas from Sabine Lake to Corpus Christi Bay are examples of the former; the Laguna Madre is representative of the latter. DIMENSIONS Each of the seven Texas estuarine study areas is described by a set of boundaries: seaward, landward, and internal (Figs. 1-3). Seward boundaries were established by custom, by the definition of estuaries by Pritchard (1967), and by procedures established by Pearcy (1959). Pritchard states that an estuary is a semienclosed coastal body of water which has a free connection with the open ocean and within which seawater is measurably diluted with freshwater derived from land drainage. Pearcy described methods for defining the geographical boundaries between bays and the territorial sea, but for purposes of this paper, the method of drawing the coastline between headlands, islands, and peninsulas will suffice. Landward boundaries of the estuarine study areas were determined by limited field observations of the landward penetration of plants characteristic of the coastal marshes and by examination of aerial photographs of the U.S. Soil Conservation Service and topographic maps of the U.S. Geological Survey. Internal boundaries between open waters of estuarine study areas were established arbitrarily except where historical precedent dictated otherwise. Inland, these boundaries approximate established boundaries of river basins, and they are used for the purpose of pollution studies contained in this report. Table 3 lists the area, depth, tidal range, and volume of major waters in the seven estuarine study areas. Areas were measured on maps of the U.S. Geological Survey and charts of the U.S. Coast and Geodetic Survey with a compensating planimeter. The values in Table 3 are averages of the results. Depths are averages of the most recent soundings at mean low water (MLW) exclusive of navigation channels. Average tidal range data are from the U.S. Geological Survey and the U.S. Army Corps of Engineers. The tides are diurnal. The volume at MLW is the product of the area and the average depth; the volume at mean high water (MHW) is the product of the area at MHW and the average depth plus average tidal range. Intertidal volume is the difference between the two volumes. The total open water area major estuaries of the Texas coast at MHW is 1,532,430 acres (620,634 hectares) or 0.74 times the area recorded for Chesapeake Bay, America's largest estuary. VEGETATION The wide variation in climate on the Texas coa

Cooperative Gulf of Mexico estuarine inventory and study, Texas : area description /