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Effects of Precipitation Events on the Movement of the Lateral Mixing Zone of the North and West Branches of the Susquehanna River at the shady Nook site Abstract The North and West branches of the Susquehanna River converge at Sunbury, Pennsylvania to create a Lateral Mixing Zone (LMZ) that extends all the way downstream from Selinsgrove after which islands help facilitate mixing. In this study, the movement of the LMZ was observed in accordance with multiple precipitation events. YSI 556 Multimeter and a boat were used to continuously take data samples across the river between sites 1, 2, 3, and 4. Site 1 is located on the West branch of the Susquehanna River while Sites 2 and 3 are located on opposite sides of Byer Island, while Site 4 is on the East bank (Figure 1). A GPS was used to track movement and help identify the location of LMZ along with the data associated with each data point of the transit. Data was collected after various periods of precipitation and discharge rates. Four Hydrolab sondes were also deployed at each site to support the identification of the water of the two branches. Water chemistry was analyzed using an Ion Chromatography System (ICS). The machine simultaneously scanned cations and anions and plotted the samples against standard curves. The anions analyzed were fluoride, chloride, nitrite, bromide, sulfate, nitrate, and phosphate. The cations analyzed were sodium, ammonium, potassium, magnesium, and calcium. Among all the measured parameters including water chemistry, physical properties from both the YSI multimeter and the sondes have demonstrated that specific conductivity produced the clearest trends of LMZ between the two branches. Compared to previous data, it was determined that as the discharge increases due to precipitation events, the LMZ moves away from the West branch and towards the North branch up until a threshold point and then slightly shifts back to the West branch. Methods Four sites along the Susquehanna River were selected to study the LMZ. Sites 1 and 2 are between the Shady Nook shore and the west shore of Byer Island, site 3 is on the opposite side of Byer Island and site 4 is on the Eastern bank of the river. YSI 556 Multimeter and a boat were used to take data samples along the transect of sites 1 and 2 as well as between sites 3 and 4. Four Hyrdolab-multimeter water quality sondes were deployed at sites 1, 2, 3, and 4 and were left for 5 days before and during various precipitation events. A GPS was used to track movement and the data was later used to help find the location of the LMZ along with the data collected from the YSI transects. Water chemistry data has been collected since 2009 and was used during this project to help determine the shifting of the LMZ. The water chemistry data that was taken included temperature, specific conductivity, pH, salinity, dissolved oxygen, saturated dissolved oxygen, and oxidation reduction potential. Discharge data was obtained from the United States Geological Survey (USGS) from sites 01554000, 01540500, and 01553500 and precipitation data was obtained from Weather Underground. Figure 1: Location of Sites 1-4. Figure 3: Movement of LMZ between sites 1 and 2. Tyler Menz 1 , Ahmed Lachhab 1 and Brian Zuidervliet 2 1 Susquehanna University, Earth & Environmental Sciences, Selinsgrove PA, 17870. 2 Bucknell University, Environmental Engineering, Lewisburg, PA 17837 Figure 4: Transect between sites 3 and 4. Results Specific conductivity has produced the clearest trends of LMZ between the two branches (Figure 2). As the discharge increases due to precipitation events, the LMZ moves away from the West branch and towards the North Branch. Acknowledgements: The Degenstein Foundation for funding this project T(C) 22 23 24 25 pH 8.1 8.2 8.3 8.4 8.5 ORP 100 150 200 K 180 200 220 240 Sal 0.08 0.09 0.1 0.11 0.12 TDS 0.1 0.15 0.2 h(m) 0 1 2 DO 7.4 7.6 7.8 8 CHL 1.5 2 2.5 3 3.5 Turb 0 1 2 pH 6.8 6.85 6.9 6.95 7 ORP 220 240 260 280 k 200 220 240 260 Sal 3 3.5 4 TDS 0.1 0.15 0.2 T 23 23.5 24 24.5 25 h(m) 2.4 2.5 2.6 Turb -0.2 0 0.2 0.4 0.6 DO 0.22 0.24 0.26 0.28 CHL 0 2 4 6 T 21 22 23 24 25 pH 7.8 8 8.2 8.4 ORP 150 200 250 K 200 300 400 500 600 Sal 0.1 0.15 0.2 0.25 0.3 TDS 0.1 0.2 0.3 0.4 h 1.5 2 2.5 3 Turb 0 50 100 DO 6.5 7 7.5 CHL -0.5 0 0.5 T 21 22 23 24 25 pH 8 10 12 14 ORP -1000 -500 0 K 0 200 400 600 Sal 0 0.1 0.2 0.3 TDS 0 0.1 0.2 0.3 0.4 h 1.5 2 2.5 Turb -0.5 0 0.5 DO 6.5 7 7.5 8 CHL -0.5 0 0.5 The LMZ will move towards the North branch up until a threshold point after which it shifts slightly back towards the West branch. Data from the ICS was averaged across all four sites to produce a chemical analysis of the river as a whole (Figure 5). We are also considering tracking the LMZ at its merging point in Lake Augusta near Sunbury, PA. Figure 5: Cation and anion data from the ICS 0 5 10 15 20 1 2 3 4 Na 0 10 20 30 1 2 3 4 Ca 0 5 10 1 2 3 4 Mg 1 1.5 2 2.5 1 2 3 4 K 0 0.2 0.4 1 2 3 4 NH4 25 30 35 40 1 2 3 4 Br 0.05 0.06 0.07 0.08 1 2 3 4 F 0 1 2 3 1 2 3 4 PO4 0.05 0.1 0.15 0.2 1 2 3 4 NO2 0 50 100 1 2 3 4 NO3 0.1 0.12 0.14 0.16 1 2 3 4 Sites SO4 0 10 20 30 1 2 3 4 Sites CHL Susquehanna Valley Undergraduate Research Symposium
