Autonomous Underwater Vehicle Water-Quality Measurements in Savannah River, Savannah, Georgia, 2018-2019

The Savannah Harbor Expansion Project (SHEP) began in January 2015 with the purpose of deepening the Savannah Harbor federal shipping channel to allow access to larger shipping vessels (U.S. Army Corps of Engineers, 2018a). There are various features and mitigation efforts to the SHEP, one of which is the installation of a dissolved-oxygen (DO) injection system at two locations along the Savannah River to maintain pre-SHEP DO levels in the harbor (U.S. Army Corps of Engineers, 2018b). The injection systems are installed upstream near Georgia Power Plant McIntosh in Effingham County, Georgia and downstream near Hutchinson Island, Chatham County, Georgia. Designed to maintain DO levels in the harbor as they were before deepening, the system will pull water from the river into the Speece cones and inject it with oxygen before returning it to the river (Tetra Tech, 2013).
Water-quality and bathymetric data were measured with an Autonomous Underwater Vehicle (AUV) during a spatial survey in the study area near the Hutchinson Island DO injector site in August 2018. Two AUVs were used for each trip in February, April, and May of 2019. Water-quality and bathymetric data were measured by the AUV and logged at 1-second intervals. Bathymetric data were measured using an on-board depth sounder and pressure transducer. During the August 2018, and April and May 2019 data collection, water-quality data were measured with a YSI 6600 V2 sonde mounted in the nose cone of the IVER2 EcoMapper AUV(s). During the February 2019 data collection period, an IVER3 EcoMapper AUV with an EXO1 multiparameter sonde was substituted for one of the IVER2 AUVs that was temporarily out of service. The sondes were calibrated before, and checked after, each data collection trip per USGS water-quality sampling protocols (YSI, 2012; Wagner and others, 2006; Wilde, variously dated).  See processing steps for additional information related to calibration and checks. Data were measured at various periods of the tide cycle but generally targeted at or near slack tide conditions. The February 2019 trip attempted to monitor high and low tide conditions. However, the trip coincided with a King Tide which produced higher flow and significant debris interfering with the AUVs ability to obtain all waypoints resulting in multiple aborted missions. Those missions were edited in the field based on conditions and low tide monitoring resulted in fully completed missions. Water-quality parameters measured by the AUVs during the survey may include: Specific conductivity (microSiemens per centimeter at 25 degrees Celsius; YSI sensor 6560, 599870 (EXO)), water Temperature (degrees Celsius; YSI sensor 6560, 599870 (EXO)), Salinity (parts per thousand; computed from conductivity), Phycocyanin Fluorescence (estimated as Blue-green Algae cell density in cells per milliliter; YSI sensor 6131), Chlorophyll Fluorescence (estimated in micrograms per liter; YSI sensor 6025,  599103-01 (EXO)), Rhodamine Fluorescence (micrograms per liter; YSI sensor 6130), Dissolved Oxygen (milligrams per liter; YSI optical sensor 6150, 599100-01 (EXO)), pH (standard units; YSI sensor FR 6589), and Turbidity (formazin nephelometric units; YSI sensor 6136, 599101-01 (EXO)) (YSI, 2012 and 2019).
References
Anderson, C.W., 2005, Turbidity: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6.7, https://doi.org/10.3133/twri09A6.7.  
Conrads, P.A., Journey, C.A., Petkewich, M.D., Lanier, T.H., Clark, J.M., 2018, Characterization of water quality in Bushy Park Reservoir, South Carolina, 2013–15: U.S. Geological Survey, https://doi.org/10.3133/sir20185010. 
Gibs, Jacob, Wilde, F.D., and Heckathorn, H.A., 2012, Use of multiparameter instruments for routine field measurements: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6, https://doi.org/10.3133/twri09A6.8. 
Jackson, P.R., 2013, Circulation, mixing, and transport in nearshore Lake Erie in the vicinity of Villa Angela Beach and Euclid Creek, Cleveland, Ohio, September 11–12, 2012, U.S. Geological Survey, http://dx.doi.org/10.3133/sir20135198. 
Ritz, G.F., and Collins, J.A., 2008, pH 6.4 (ver. 2.0, October 2008): U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6.4, https://doi.org/10.3133/twri09A6.4.  
Tetra Tech, Inc. 2010, Oxygen Injection Design Report Savannah Harbor Expansion Project Savannah, Georgia: Tetra Tech, Inc, https://www.sas.usace.army.mil/Portals/61/docs/SHEP/Reports/GRR/4%20Oxygen%20Injection%20Design%20Report%20October%202010.pdf.  
United States Army Corps of Engineers, 2018a, What Is The SHEP: United States Army Corps of Engineers, https://www.sas.usace.army.mil/Missions/Civil-Works/Savannah-Harbor-Expansion/What-is-SHEP/.  
United States Army Corps of Engineers, 2018b, SHEP Progression Chart: United States Army Corps of Engineers, https://www.sas.usace.army.mil/Missions/Civil-Works/Savannah-Harbor-Expansion/.  
U.S. Geological Survey, 2008, Field Measurements, (edited by Wilde, F.D.): U.S. Geological Survey Techniques of Water-Resources Investigations, book 9; chap A6, https://doi.org/10.3133/twri09A6. 
U.S. Geological Survey, 2019, Specific conductance: U.S. Geological Survey Techniques and Methods, book 9, chap. A6.3, 15 p., https://doi.org/10.3133/tm9A6.3. [Supersedes USGS Techniques of Water-Resources Investigations, book 9, chap. A6.3, version 1.2.] 
U.S. Geological Survey, 2020, Dissolved oxygen: U.S. Geological Survey Techniques and Methods, book 9, chap. A6.2, 33 p., https://doi.org/10.3133/tm9A6.2. [Supersedes USGS Techniques of Water-Resources Investigations, book 9, chap. A6.2, version 3.0.]  
Wagner, R.J., Boulger Jr., R.W. Oblinger, C.J. Smith, B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors: Station operation, record computation, and data reporting: U.S. Geological Survey, https://doi.org/10.3133/tm1D3. 
Wilde, F.D., Temperature, 2006: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. 6.1, https://doi.org/10.3133/twri09A6.1. 
Wilde, F.D., 2008, Chapter A6.0, General Information and Guidelines: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6.0, https://doi.org/10.3133/twri09A6.0. 
YSI, Inc., 2012, 6-Series Multiparameter Water Quality Sondes User Manual: YSI, Inc., https://www.ysi.com/File%20Library/Documents/Manuals/069300-YSI-6-Series-Manual-RevJ.pdf.  
YSI, Inc., 2019, EXO User Manual: Advanced Water Quality Monitoring Platform: YSI, Inc., https://www.ysi.com/File%20Library/Documents/Manuals/EXO-User-Manual-Web.pdf. 
Conrads, P.A., Journey, C.A., Petkewich, M.D., Lanier, T.H., Clark, J.M., 2018, Characterization of water quality in Bushy Park Reservoir, South Carolina, 2013–15: U.S. Geological Survey, https://doi.org/10.3133/sir20185010 

Tags: algal-blooms, back-river, chatham-county, dredging, georgia, oxygen-content-water, rivers, savannah-harbor, south-carolina, transportation, usgs-5c8c21cfe4b0938824529ffd, water-chemistry, water-quality
Organization: Department of the Interior