Measures of Environmental Performance and Ecosystem Condition (1999) / Chapter Skim
Currently Skimming:
TVA's Approach to Ecological Health Assessment in Streams and Reservoirs
TVA's Approach to Ecological Health Assessment in Streams and Reservoirs
Pages 260-284
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From page 260... ...
The TVA also carries out additional periodic monitoring of toxic contaminant levels in fish and bacteriological sampling at recreation areas to assess whether people can safely fish and swim in the Tennessee Valley waters. The ecological integrity of streams and reservoirs is evaluated as part of an activity called Vital Signs monitoring that is based on annual examinations of key physical, chemical, and biological indicators.
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From page 261... ...
With these fundamental premises in mind, TVA's challenge has been to develop a sustainable monitoring effort that collects the right kinds of data at a minimum number of locations and frequencies, yet still provides enough information to reliably characterize ecological health. The four main activities of the program focus on physical and chemical characteristics of water; acute toxicity and physical and chemical characteristics of sediment; benthic macroinvertebrate community sampling; and fish assemblage sampling.
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From page 262... ...
Consequently, Vital Signs monitoring includes only four large embayments with drainage areas greater than 500 square miles and surface areas greater than 4,500 acres. Locations for stream monitoring stations are chosen to sample as large a portion of each tributary watershed as possible.
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From page 263... ...
For reservoirs where aerial photography is not carried out, standard field surveys and historical information are used to estimate aquatic plant community structure and coverage. Submersed aquatic plant populations generally are rare in tributary reservoirs because of the wide fluctuations of water surface elevations associated with their operation for floodwater storage.
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From page 264... ...
264 NC NEIL E CARRIKER FIGURE 2 Reservoir Vital Signs monitoring locations, 1994.
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From page 265... ...
WV VA 1 Clarks River North Fork 15 Holston River KENTUCKY 13 Powell River 12 Clinch River 14 Holston River 16 Nolichucky River TENNESSEE 11 Emory River 17 French Broad River 2 Duck River 18 Pigeon River NC 3 Buffalo River 10 Tuckasegee River 6 Sequatchie River Little Tennessee 8 Hiwawsee River 9 River 5 Elk River 7 Ocoee River SOUTH CAROLINA TVA'S ECOLOGICAL ASSESSMENT OF STREAMS AND RESERVOIRS 4 Bear Creek MISS ALABAMA GEORGIA 265 FIGURE 3 Stream Vital Signs monitoring locations, 1994.
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From page 266... ...
Of the many variables it collects, TVA has selected five indicators for evaluating reservoir health: dissolved oxygen, chlorophyll-a, sediment quality, benthic macroinvertebrates, and fish community. Stream evaluation is based on four aquatic ecosystem indicators: nutrient concentrations, sediment quality, benthic macroinvertebrates, and fish community.
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From page 267... ...
If this phenomenon persists long enough, these chemicals can cause chronic or acute toxicity to bottom-dwelling animals. Historic information for reservoirs in the Tennessee Valley reveals that the burrowing mayfly (Hexagenia sp.)
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From page 268... ...
268 Elevation (ft above mean sea level) Distance across Reservoir (ft)
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From page 269... ...
, and BDO is a 6-month average of the percent of reservoir cross-sectional bottom length at the sampling location that has a DO concentration less than 2.0 mg/l. The overall DO rating is the average of the DO ratings of water column and the bottom.
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From page 270... ...
is compared with these criteria and rated accordingly. Sediment Quality Contaminated bottom sediments can have direct adverse impacts on bottom fauna and can often be long-term sources of toxic substances in the aquatic environment.
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From page 271... ...
TVA's approach combines two assessment methods, one biological and one chemical, to evaluate reservoir sediment quality. TVA's scoring criterion is based on ratings for the toxicity of sediment pore water (STOX)
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From page 272... ...
, with scoring criteria specific to either run-of-the-river or storage reservoirs, are used to evaluate the ecological health of the benthic macroinvertebrate community: • Taxa richness, or the number of different taxa present. More taxa indicate better conditions.
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From page 273... ...
Because of the distinct habitat differences among reservoirs and sampling locations (and the differences in the fish assemblages that they support) , different scoring criteria are used according to reservoir type (runof-the-river or tributary storage reservoirs)
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From page 274... ...
is not yet enough information for inflow sampling locations on tributary reservoirs to establish criteria for fish community metrics at those sites. The average of the sum of the electrofishing scores and the sum of the gill netting scores results in a RFAI for each station.
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From page 275... ...
• Percentage insectivores -- Due to the special dietary requirements of this group of species and the limitations of their food source in de graded environments, the proportion of insectivores increases with environmental quality. Reservoir Fish Reproductive Composition Metric • Number of lithophilic spawning species -- Lithophilic broadcast spawn ers are sensitive to siltation.
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From page 276... ...
Particular emphasis is given to the relationship between conditions at stream stations and their potential impact on downstream reservoirs. The evaluations consider four indicators: total phosphorus, a measure of nutrient enrichment and potential for excessive algal productivity; sediment quality; benthic community; and fish community.
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From page 277... ...
The scoring criterion is based on a rating for the acute toxicity of sediment pore water to both the rotifer Brachionus calyciflorus and the daphnid Ceriodaphnia dubia, and a rating for the sediment concentrations of heavy metals, PCBs, organochlorine pesticides, and un-ionized ammonia. The final sediment quality rating is the average of these two ratings.
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From page 278... ...
All other metrics applied to individual quantitative samples and resultant scores averaged. Benthic Community A modified version of the Benthic Index of Biotic Integrity (Kerans et al., 1992)
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From page 279... ...
against values that would be expected at reference sites. The 12 metric scores are summed to produce an index ranging from 12 to 60, and the fish community at the stream sampling location is rated as poor (index <36)
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From page 280... ...
100 280 Ecological Health Indicators Sediment Benthos Fish Community DO Chlorophyll Good 80 Fair 60 Rating Poor 40 20 0 ky k n r ille ck a r un ico ky tuc k wic lso e ele sv aja aug Ba do ell tuc n Wi r k tts ou ll T en Ke Pic Wh nte Nic am Wa Hi K Gu ick rt L Ch Fo on M elt FIGURE 5 Overall ecological health of run-of-the-river reservoirs in the Tennessee Valley in 1993.
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From page 281... ...
Three, the Clinch, Powell, and Little Tennessee Rivers, had the highest possible scores for all four ecological health indicators (nutrients, sediment, benthic macroinvertebrates, and fish community)
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From page 282... ...
as other reservoirs to facilitate comparisons. than five indicators; indicator and overall scores are shown on the same scale FIGURE 6 Overall ecological health of tributary reservoirs in the Tennessee Valley in 1993.
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From page 283... ...
1992. Reservoir Vital Signs Monitoring -- 1991: Summary of Vital Signs and Use Impairment Monitoring on Tennessee Valley Reservoirs.
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