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BAYS AND ESTUARIES
ASSESSMENT AND IMPAIRMENT
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Source: TCEQ, 2002 Water Quality Inventory, September 2002, Table 10-2.
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Estuaries and bays are threatened by a variety of pollution sources and are among Texas's most
endangered waters. For the most recent water quality inventory, 57 estuaries - covering some 2,004 square miles -- were surveyed, while another 390 square miles of bays and estuaries were not.* Of the bays and estuaries surveyed, sufficient data was available to assess some 86.2 percent, or over 1,725 miles. Some
21 percent of the assessed bays and estuaries did not fully meet their designated uses under the state's water quality standards.* These uses include swimming
(contact recreation), oyster harvesting, fish consumption, aquatic life, and "general" uses.
Most of these water quality problems are related to high levels of fecal coliform bacteria and other
pathogens in Texas's shellfish harvesting areas. To protect public health, the Texas Department of Health administers the National Shellfish Sanitation Program in
Texas and monitors pathogen levels in shellfish. In its 2002 report, the TCEQ reported that, of the 32 segments that have been designated to support oyster
waters, the TDH found that 15 -- including all of Nueces Bay, Cedar Lakes, and Chocolate Bay and major portions of Upper Galveston Bay, Trinity Bay, Lower
Galveston Bay, and Carancahua Bay -- had fecal coliform contamination levels above the water quality standards that determine nonsupport of the use.* In addition to these impairments, since 1990, the TDH has kept a fish consumption
advisory in place for Upper Galveston Bay, Tabbs Bay, San Jacinto Bay, Black Duck Bay, Scott Bay, Burnett Bay, Barbours
Cut and the Bayport Channel due to elevated dioxin levels in catfish and blue crabs because of dioxin contamination
from paper mills. In addition, parts of Lavaca and Cox bays have been closed to fish and blue crab harvesting
(consumption) since 1988 because of elevated levels of mercury related to an industrial point source and mercury spills.* One segment—the Oso Bay -- did not fully meet its aquatic life use due to depressed dissolved oxygen levels,
probably due to reduced freshwater inflows in the summer months, although several other bays were listed as having "concerns" for low levels of oxygen.*
Finally, the TCEQ identified a number of "concerns" in bay and estuary waters, including nutrient loading in Clear Lake
and the Laguna Madre -- leading to high levels of chlorophyll a -- and elevated levels of metals in sediment in the Old Brazos River Channel and Lavaca/Chocolate Bay.*
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USE SUPPORT SUMMARY FOR BAYS AND ESTUARIES, 2002
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USE
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TOTAL MILES ASSESS ED
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MEET USE
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IMPAIRED
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SURVEYED, BUT NOT ASSESSED
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Aquatic Life Support
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971.28
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969.5
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1.78
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1,032.7
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Contact Recreation
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1,518.8
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1,518.8
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0
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480
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Fish Consumption
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281.9
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244.9
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37
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1,722
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Oyster Waters
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1,625.7
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1,084.1
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339.8
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346.1
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Source: Texas Commission on Environmental Quality, 2002 Texas Water
Quality Inventory, (September 2002), Table 10-1, 10-2 and 10-3.
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CAUSES PRESENT IN IMPAIRED BAYS AND ESTUARIES
(% OF IMPAIRED SQUARE MILES), 2002
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Source: Texas Commission on Environmental Quality, 2002 Texas Water
Quality Inventory, (September 2002), 10-5.
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RISKS TO BAYS AND ESTUARIES
- Dams and reservoirs. These structures stem
the regular flow of rivers feeding the estuaries.
- Upstream water use. Diversion of water from
rivers decreases estuary inflow. New surface water use permits sometimes require that a portion of fresh water be set aside to protect the inflow needs of estuaries. But fresh surface
water is not always available because surface water rights in most rivers in Texas have already been fully allocated. Instead, estuaries must often rely on return flows from wastewater
treatment plants.
- Floods. Land development increases the amount
of impervious cover, which in turn increases the rate of surface water runoff that eventually reaches the estuaries. The wetlands surrounding
estuaries act as natural filtering systems for pollutants, and these systems' filtering abilities can be overwhelmed when large volumes of water, some of it contaminated with
non-point-source pollution, rush in after periods of heavy rainfall.
- Drought. In periods of little rainfall, municipalities, agriculture, and industry all use more water.
- Toxic pollution. Toxic contaminants like metals and pesticides can settle into estuaries and bays and remain
there for years. Dredging can stir them back into the water and into the aquatic-life food chain.
- Nutrients. Municipal and industrial wastewater discharges, leaky sewers, and runoff from cities, suburbs, and
farms can all increase the loading of nutrients (nitrogen and phosphorus) to the estuaries. While some level of
nutrients is needed for plant life, too much can lead to an overabundance of algae and eventually to loss of
dissolved oxygen, which reduces animal life and ultimately damages the overall health of the estuary.
- Oil spills and marine pollution. Thousands of oil spills along the coast and offshore, as well as illegal dumping
of trash, impact coastal waters.
- Untreated sewage. The Army Corps of Engineers estimates that 1.2 million gallons per day of partially treated
sewage flows into the Rio Grande from the city of Reynosa, only about 60 miles from the Gulf of Mexico.* The
city of Matamoros discharges an estimated 2.5 million gallons a day of completely untreated wastewater into a
canal that flows into the Gulf of Mexico, about 23 miles south of the international border.* Prevailing southeast
winds drive it up toward the Texas coast. Fortunately, in 2003, both Matamoros and Reynosa were building new wastewater treatment plants, which should help clean up these waters.
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SOURCES PRESENT IN IMPAIRED BAYS AND ESTUARIES, 2002
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SOURCE
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% OF IMPAIRED SQ. MILES
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Unknown Point and Nonpoint Sources
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95%
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Municipal Point Sources
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3%
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Spills
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1%
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Industrial Point Sources
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10%
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Source: Texas Commission on Environmental Quality, 2002 Texas Water
Quality Inventory, (September 2002), 10-5.
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