Probabilistic Monitoring of Streams Below Small Impoundments in Tennessee

1. Probabilistic Monitoring of Streams Below Small Impoundments in Tennessee Debbie Arnwine Water Pollution Control 615-532-0703 Debbie.Arnwine@tn.gov

2. 2003 probabilistic study of 75 streams downstream of small impoundments • Macroinvertebrates • Nutrients • Dissolved Oxygen • Temperature • pH • Suspended Solids • Iron and manganese • Habitat • Flow and morphology • Periphyton Density

3. Over 195,000 small man-made lakes and ponds in Tennessee 1,302 recorded in databases Potential for public access (safe dams) Built after 1992 (ARAP)

4. Site Selection Random Selection 75 impounded streams < 250 acres

5. Perennial stream with sufficient flow (during recon) to provide macroinver-tebrate habitat.

6. Suitable habitat to use TDEC’s semi-quantitative protocols Rooted Bank Habitat Riffle Kicks

7. Comparable bioregion and size to existing reference streams or project-specific reference

8. Upstream Reference not Feasible • Impoundment flooded entire headwaters • Second impoundment immediately upstream • Drainage area upstream not 80% within same bioregion. • Stream size too small upstream of impoundment.

9. One upstream site was suitable.

10. Minimum observable impacts not associated with impoundment

11. Impoundments built for agricultural purposes were included. Livestock pens built on dam.

12. Accessible

13. Site reconnaissance(200 recons to get 75 sites)

14. Site Characterization • Impounded 1960 - 1980 (50%) • Surface Discharge (69%) • Forested Drainage Area (77%) • 2nd Order Stream (53%) • < 50 acres (70%)

15. Macroinvertebrate Samples Semi-quantitative Single Habitat Spring and Fall Tennessee Macroinvertebrate Index (TMI) • Taxa Richness • EPT Richness • %EPT • %OC • NCBI • %Dominant • %Clingers • Ky % Nutrient Tolerant

16. 95% Failed to Meet Biocriteria

17. Individual Biometrics

18. Dominant taxa indicative of nutrients and/or sluggish flow Fall: Dominant = Cheumatopsyche and Glyptotendipes spp. Spring: Dominant = Lirceus, Parametriocnemus and Polypedilum spp.

19. Example of biological data pre and post impoundment

20. FLOW 52% insufficient flow to sustain aquatic life at least one season (25% dry).

21. Precipitation generally at or above 25 year average

22. Headwater reference sites had adequate flow every season.

23. Comparison of discharge types

24. Geomorphology 49% relative stable channels typical of ecoregion 24% “G-type” –deeply entrenched, unstable banks, heavy sediment loads

25. 20% E-Type in response to lack of flow. Small channel cut within original stream bed.

26. Dominant bed material becomes smaller below impoundments

27. HABITAT70% of sites failed overall habitat

28. Dissolved Oxygen Based on instantaneous day time measurement

29. DO Measurements do not tell the whole story. • Instantaneous measurement during daylight hours. • Presence of algae at most sites indicates possible large diurnal swings. • 17% of sites supersaturated. • Percent saturation at 77% of sites below 10th percentile of reference data.

30. TEMPERATURE11% of sites exceeded criteria.72% above fall reference temps.

31. pH 5% of sites had low pH

32. Suspended Solids 50% of sites had elevated suspended solids. Land use associated with small impoundments contributes to the problem.

33. Iron and Manganese 61% of sites above recommended iron criterion of 1000 ug/L 93% of sites above reference levels for manganese

34. Nutrients 41% exceeded NO2+NO3 criteria at least one season. 75% exceeded total phosphorus criteria at least one season.

35. Periphyton

36. Detailed Report http://www.tn.gov/environment/wpc/publications/ (or at the back of the room!) Probabilistic Monitoring of Streams Below Small Impoundments in Tennessee

37. QUESTIONS? www.tn.gov/environment/wpc/publications/ Debbie Arnwine Water Pollution Control 615-532-0703 Debbie.Arnwine@tn.gov