1. Light-scattering Features of Turbidity-causing Particles in Interconnected Reservoir Basins and a Connecting Stream Upstate Freshwater Inst. Feng Peng and Steven W. Effler Upstate Freshwater Institute, Syracuse, New York Donald C. Pierson NYC Department of Environmental Protection David G. Smith National Institute of Water and Atmosphere, New Zealand

2. Study System  turbidity as a water quality issue

3. Character of Light-scattering (Turbidity-causing) Particles within the Catskill System Related questions  What are the light-scattering characters of particles (size distributions, composition, shape) in the Catskill system?  Are there differences in the light scattering characteristics of particles in different parts of the Catskill System?  Does the potential difference cause disproportionate contributions of the source particles to turbidity (T n ) within the system?

4. Turbidity (T n ): A Measure of Light Scattering (light scattering coefficient, b; m  1 ) T n measured at acceptance angle centered at 90  (“side-scattering”) Tn  bTn  b 0º0º 90º

5. Light scattering coefficient (b) depends on four features of particle population 1.particle number concentration (N) 2.particle size distribution (PSD) 3.particle composition (i.e., refractive index) 4.particle shape Particle characterizations bulk measurements of mass (TSS) and mass fractions; disconnect with light scattering PSDs  counters; size limitations, no chemical composition SAX §  individual particle analysis; N, PSD, composition, and shape Particles and Light Scattering : Dependencies and Analytical Support § scanning electron microscopy interfaced with automated image and X-ray analyses

6. Individual Particle Analysis (IPA)  by Scanning electron microscopy interfaced with Automated image and X-ray analyses (SAX) Detailed compositional and morphological analyses

7. SAX Characterizations § Chemical (elemental X-rays)  5 inorganic particle types, including clay minerals, quartz Morphological  rotating chord algorithm PA i  sum of all triangular areas d i  area equivalent diameter shape  “nonsphericity”, ASP (aspect ratio) = D max /D perp >1,000 particles analyzed in each sample § Peng and Effler (2007) Limnol. Oceangr. 52: 204  216. Peng et al. (2009) Water Res. 43: 2280  2292.

8. V  sample volume N  number of particles per unit volume of water Q b,i  light scattering efficiency of particle i; Mie theory m i  (complex) relative refractive index of particle i (n i  in); depending on composition  wavelength d i  size of particle i PA i  projected area of particle i Calculation of b from SAX Measurements  according to light scattering theory light

9. System Configuration, and Sampling (2005) for SAX Characterizations Sites (n = 9) Schoharie  site 3 and withdrawal Esopus  AP (above portal), E16i Ashokan  sites 3 and 1 (W. basin), site 4 (E. basin) Kensico  sites 4.2 and 4.1 Runoff Conditions (Q) low Q and T n ; high Q and T n Tunnel Operations on/off Schoharie Res. Ashokan Res. Kensico Res. Esopus Creek Shandaken Tunnel Catskill Aqueduct

10. Dependency of b on Size (calculated from SAX results) Particle Size Distribution (SAX observation) Esopus Creek, E16i 13 Apr 2005 T n 66.7 NTU 50% d 50 = 2.70  m d 25 d 75

11. Scenarios of Interest in the Catskill System  related to the relative contribution of Schoharie Reservoir (diversions, Shandaken Tunnel) Evaluating the potential for T n from Schoharie Reservoir (T n/SCH ) making a disproportionately large contribution to T n leaving the east basin of Ashokan (T n/ASH ) to Kensico 2. shape: ASP SCH >> ASP Esop ?? i.e., greater deviation from sphericity 3. size: d 50/SCH << d 50/Esop ?? Systematically smaller particles would settle more slowly (i.e., persistence) 1. composition (i.e., refractive index): ??

12. Particle Composition for Sites throughout the Catskill Systems Sites No. of Samples T n range b(660) Range % of b (mean ± std. dev.) (NTU)(m  1 )ClayQuartzSi-richFe/MnMisc. SCH R. 200253 4.2  812.4  46.4 82.5 ± 3.18.3 ± 2.73.8 ± 1.21.7 ± 0.83.6 ± 1.6 20059 2.2  4400.8  203.7 86.1 ± 7.58.1 ± 5.82.8 ± 1.31.0 ± 0.51.9 ± 0.6 AP 20056 1.5  760.7  44.4 76.6 ± 2.912.5 ± 2.84.9 ± 2.21.2 ± 0.44.6 ± 3.4 E16i 20054 2.7  671.0  44.9 77.6 ± 4.613.4 ± 4.45.0 ± 1.21.0 ± 0.73.0 ± 0.9 ASH W. 20056 1.6  4640.7  336.2 76.8 ± 2.214.8 ± 2.65.0 ± 1.51.1 ± 0.42.3 ± 0.6 ASH. E. 20052 2.6  31.81.0  15.9 78.0 ± --13.4 ± --4.9 ± --1.0 ± --2.7 ± -- Kensico 20052 1.6  220.8  14.3 79.5 ± --11.8 ± --4.9 ± --1.5 ± --2.3 ± -- Answer to question 1: compositionally uniform

13. Particle Shapes (ASP Values) for Sites throughout the Catskill Systems SitesSamples ASP nmean ± std. dev. Schoharie R. 2002531.75 ± 0.09* 200592.16 ± 0.2 Esopus AP 200561.90 ± 0.08 Esopus E16i 200541.90 ± 0.03 Ashokan R. W. 200562.03 ± 0.2 Ashokan R. E. 200521.98 ± -- Kensico R. 200522.35 ± -- * ‘Clay’-type particles only (Peng and Effler, 2007. Limnol. Oceanogr.) Answer to question 2: similar morphology (ASP SCH  ASP Esop )

14. Uniformity of Particle Size Distributions in the Catskill System in the Context of Light Scattering (i.e., T n ) Apr 2005, wet conditionsRelatively minor variations in sizes regulating b and therefore, T n Quartile Sizes (μm) d 25 d 50 d 75 SCH R.1.712.544.17 Intake1.672.433.88 AP1.842.744.69 E16i1.782.664.52

15. Comparison of Particle Size Contributions to b (T n )  Esopus Creek example Very similar particle size dependencies over stream length

16. Comparison of Particle Size Contributions to b (T n )  Esopus Creek example, tunnel on/off T n AP, 18.8 E16i, 23.0 AP, 76.1 E16i, 66.7

17. Quartile Sizes of Scattering for Sites throughout the Catskill Systems ( Wet Conditions, Apr 2005) Schoharie Res. Ashokan Res. Kensico Res. Esopus Creek Shandaken Tunnel Catskill Aqueduct

18. Answer to question 3: The analyses of PSDs and the size dependency patterns of b indicate that –particles from Schoharie Intake were not noticeably smaller than those from the Esopus watershed.

19. SAX-based Estimate as Strong Predictor of Turbidity  technique credibility Significance: SAX provides representative specifications of T n -causing attributes of particles in the Catskill System SAX can be used to address the issue of potential heterogeneity in light scattering and settling within this system Good closure

20. Summary Highly uniform light-scattering (thus turbidity-causing) properties of the suspended particles throughout the Catskill system over a wide range of turbidity –composition (clay minerals dominating) –size distribution –shape Similar potencies of particle populations in upstream vs. downstream turbidity sources Findings support –direct incorporation of T n measurements into loading calculations to evaluate source impacts –parameterization of mechanistic turbidity models; e.g., representations of particles in the turbidity models for Schoharie, Ashokan, and Kensico Published manuscript Peng, F., S.W. Effler, D. C. Pierson, and D. G. Smith. 2009. Light-scattering features of turbidity-causing particles in interconnected reservoir basins and a connecting stream. Water Research 43(8): 2280–2292.