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SUMMARY OF MAJOR ISSUES AND FINDINGS IN THE TRINITY RIVER BASIN

| Contents | Environmental Setting |

Nutrients in streams

Nutrients in tributary streams rarely are at concentrations unacceptable for drinking water.

Pesticides in streams

Pesticides are in most streams. Much of the streamflow is captured by reservoirs, which are sources of drinking water.

Determining water-quality trends using sediment cores

Lead, DDT, and polychlorinated biphenyl (PCB) concentrations have decreased, but chlordane, polycyclic aromatic hydrocarbon (PAH), and zinc concentrations have increased in sediments from urban streams since the mid-1960s.

Organochlorines in streambed sediments and aquatic biota

Concentrations of some toxic compounds in sediments commonly exceed Texas Natural Resource Conservation Commission screening concentrations.

Stream-habitat characteristics and fish-community degradation

Fish communities are affected by characteristics of streamflow and the structure of physical habitats in the stream channel, in addition to water chemistry. In streams where historical patterns of streamflow have been altered by channelization, degradation in the fish community has occurred.

Use of a new method, semipermeable membrane device (SPMD), to assess the occurrence of water-borne PAHs in streams

The SPMD is an effective tool to detect trace organic compounds in water. The small concentrations of many compounds in streams might not be detected by more traditional water-sampling techniques.

Fish-community changes reflect water-quality improvements

Improvements in the treatment of wastewater in the Dallas-Fort Worth area from the early 1970s through the mid-1990s have been beneficial to the water quality of the Trinity River.

Quality of ground water in aquifer outcrops

Pesticide, volatile organic compound (VOC), and elevated nutrient concentrations were present in some shallow (outcrop) water wells in urban and agricultural areas; however, most samples did not exceed drinking-water standards.




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