Slug additions are often the most accurate method for determining discharge when traditional current meter or acoustic measurements are unreliable because of high turbulence, rocky streambed, shallow or sheet flow, or the stream is physically inaccessible (e.g., under ice or canyon walls) or unsafe to wade (Zellweger et al., 1989, Kilpatrick and Cobb 1984, Ferranti 2015). The slug addition method for determining discharge requires an injection of a known amount of a single salt and high-frequency downstream measurement of solute concentration to capture the response curve (Kilpatrick and Cobb 1984). A new slug method was developed to determine stream discharge utilizing specific conductance and ionic molal conductivities to quantify the downstream salt concentration. The new method adopts an approach that accurately calculates the specific conductance of natural waters (McCleskey, et al., 2012). The main advantage of the new method is high-frequency measurements of specific conductance are easily obtained and the method does not require collection or analyses of discrete samples, allowing for more rapid and less expensive measurements. Data from twenty-nine slug additions are presented. The data were used to evaluate the performance of the new discharge method by comparing with discharge estimates obtained by other means (Manning et al. 2022; McCleskey et al., 2021; U.S. Geological Survey, 2022). File information: SlugAdditions.csv is a tab separated file containing details of each slug addition including stream location, date and time, type and mass of salt added, and discharge determined by an alternative method are presented. SlugAdditions_SC.csv is a tab separated file containing high-frequency specific conductance data collected from twenty-nine slug addition tests. FourmileWQ.csv is a tab separated file containing water quality data from eight different slug addition tests in Fourmile Creek, CO. Specific conductance was calculated and compared to field measurements to demonstrate the validity of the approach. Discharge.xlsx is an Excel spreadsheet that calculates discharge using high-frequency specific conductance data collected downstream from a slug addition. SaltMass.xlsx is an Excel spreadsheet that calculates the salt mass used in the slug addition. References Cited Ferranti, F., 2015. Validation Of Salt Dilution Method For Discharge Measurements In The Upper Valley Of Aniene River (Central Italy). Recent Advances in Environment, Ecosystems and Development. Kilpatrick, F.A. and Cobb, E.D., 1984. Measurement of discharge using tracers. U. S. Geological Survey Open-File Report 84-136. McCleskey, R.B., Nordstrom, D.K., Ryan, J.N. and Ball, J.W., 2012. A new method of calculating electrical conductivity with applications to natural waters. Geochimica et Cosmochimica Acta, 77(0): 369-382. McCleskey, R.B., Antweiler, R.C., Andrews, E.D., Roth, D.A. and Runkel, R.L., 2021. Streamflow and water chemistry in the Tenaya Lake Basin, Yosemite National Park, California. U.S. Geological Survey data release, https://doi.org/10.5066/P9X3WI80. U.S. Geological Survey, 2022. USGS water data for the Nation: U.S. Geological Survey National Water Information System database. accessed July 28, 2022, at https://doi.org/10.5066/F7P55KJN. Zellweger, G.W., Avanzino, R.J. and Bencala, K.E., 1989. Comparison of tracer-dilution and current-meter discharge measurements in a small gravel-bed stream, Little Lost Man Creek, California. U.S. Geological Survey Water-Resources Investigations Report 89-4150.