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CAUSES FOUND IN IMPAIRED RIVERS AND STREAMS
(% OF IMPAIRED MILES), 2002
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Source: TCEQ, Draft 2002 Texas Water Quality Inventory, 2002, 8-5.
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The major causes of pollution in surface water in Texas
are elevated levels of bacteria, low dissolved oxygen, metals or other toxics such as organics in water and fish and elevated concentrations of dissolved solids,
salinity or sulfates. Overall, in Texas, at least part of over 190 water body segments have been impacted enough by high bacteria levels in water or shellfish to
be considered "impaired," while depressed dissolved oxygen levels have impacted portions of 103 segments. Other causes of impairment include high metal content
in fish or shellfish (18 segments), high concentrations of organics -- such as PCBs or Dioxins -- in fish (19), and elevated concentrations of dissolved solids (12),
chlorides (8 segments), metals (7 segments) in water.*
However, each type of water body is impacted by different types of impairment. Major contributors to
nonsupport of uses in bays included elevated bacteria and organics in shellfish and depressed dissolved oxygen contents. In the streams and rivers, the most
frequently violated water quality standards were those for pathogens (high levels of fecal coliform or other bacteria), depressed dissolved oxygen levels, and, in some areas,
toxics such as metals and pesticides. Excess plant nutrients (nitrogen and phosphorus among others) also were
identified as a concern in some waters of the state, although specific standards have yet to be developed. In reservoirs,
impairment of use was related to elevated levels of metals --mainly mercury -- in fish, high levels of dissolved solids and pH imbalance, where the water is either too acidic or too basic.*
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CAUSES FOUND IN IMPAIRED LAKES AND RESERVOIRS
(% OF IMPAIRED ACRES), 2002
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Source: TCEQ, Draft 2002 Texas Water Quality Inventory, September 2002, 9-5.
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According to the 2002 Water Quality Inventory and data drawn from the state's limited monitoring of
toxics, five stream and river water bodies -- covering approximately 200 miles -- have toxicity levels so high they do not meet their use for aquatic
life. In addition, the TCEQ has identified 16 segments of concern for toxic substances --mainly metals -- in ambient water where further testing is
needed, as well as 8 segments where at least two tests evidenced in-stream toxic effects from water or sediment. Ambient water toxicity is due to metals
such as cadmium, zinc, lead, silver, and aluminum, while malathion, an organic substance, has exceeded chronic screening levels in the Neches River Tidal.*
The sources of water pollution typically fall into one of two categories: point-source pollution and non-point-source pollution. The term point-source pollution refers to pollutants discharged from one
discrete location or point, such as an industry or municipal wastewater treatment plant. Pollutants
discharged in this way might include, for example, fecal coliform bacteria and nutrients from sewage, and toxics such
as heavy metals, or synthetic organic contaminants.
The term non-point-source pollution refers to pollutants that cannot be identified as coming from one discrete location
or point. Examples are oil and grease that enter the water with runoff from urban streets, nitrogen from fertilizers and
pesticides, and animal wastes that wash into surface waters from agricultural lands. Natural and unknown causes of
pollutants also can impact water quality and may be related to human activities. For example, highway or housing
construction may help precipitate the runoff of natural pollution sources, such as sediment. According to the most
recent Water Quality Inventory, however, the source of most pollution in Texas' impaired water bodies is unknown.
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SOURCES PRESENT IN IMPAIRED SURFACE WATERS, 2002
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RIVERS AND STREAMS
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LAKES AND RESERVOIRS
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SOURCE
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% OF
IMPAIRED MILES
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SOURCE
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% OF
IMPAIRED ACRES
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Unknown Source
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52%
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Atmospheric Deposition
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72%
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Unknown Nonpoint Source
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51%
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Unknown Source
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16%
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Unknown Point Source
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33%
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Unknown Nonpoint Source
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16%
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Municipal Point Souces
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23%
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Unknown Point Source
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12%
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Agriculture
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17%
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Natural Source
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3%
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Urban Runoff / Storm Sewers
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17%
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Industrial Point Source
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2.5%
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Natural Sources
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13%
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Urban Runoff / Storm Sewers
|
2%
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Industrial Point Sources
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10%
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Source Outside State Borders
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9%
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Confined Animal Feeding Operations Non-Point Source
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7%
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CAFO Point Source
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7%
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Crop-Related Source
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7%
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Hydromodification
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7%
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Irrigated Crop Production
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6%
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Flow Regulation
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6%
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Source: TCEQ, Draft 2002 Texas Water Quality Inventory, 2002, 8-5 and 9-5.
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