Greg Koltun
Biography
Education:
Master of Science, Civil Engineering, The Ohio State University
Bachelor of Science, Microbiology, The Ohio State University
Professional Affiliations:
Member - American Society of Civil Engineers
Professional Experience:
1980 - Present Hydrologist, U.S. Geological Survey, Columbus, Ohio
1978 - 1980 Environmental Scientist, Ohio E.P.A., Columbus, Ohio
Science and Products
Trends in streamflow and concentrations and flux of nutrients and total suspended solids in the Upper White River at Muncie, near Nora, and near Centerton, Indiana
The U.S. Geological Survey (USGS), in cooperation with The Nature Conservancy, completed a study to estimate and assess trends in streamflow and annual mean concentrations and flux of nutrients (nitrate plus nitrite, total Kjeldahl nitrogen, and total phosphorus) and total suspended solids at three USGS streamgages (hereafter referred to as “...
Koltun, G.F.
Flood-frequency estimates for Ohio streamgages based on data through water year 2015 and techniques for estimating flood-frequency characteristics of rural, unregulated Ohio streams
Estimates of the magnitudes of annual peak streamflows with annual exceedance probabilities of 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, and 0.002 (equivalent to recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years, respectively) were computed for 391 streamgages in Ohio and adjacent states based on data collected through the 2015 water year...
Koltun, G.F.
Geospatial tools effectively estimate nonexceedance probabilities of daily streamflow at ungauged and intermittently gauged locations in Ohio
Study regionThe state of Ohio in the United States, a humid, continental climate.Study focusThe estimation of nonexceedance probabilities of daily streamflows as an alternative means of establishing the relative magnitudes of streamflows associated with hydrologic and water-quality observations.New hydrological insights for the regionSeveral...
Farmer, William H.; Koltun, G.F.
Estimation of upstream water use with Ohio’s StreamStats application
This report describes the analytical methods and results of a pilot study to enhance the Ohio StreamStats application by adding the ability to obtain water-use information for selected areas in the northeast quadrant of Ohio. Water-use estimates are determined in StreamStats through a simple multistep process. Water-use data used to develop...
Koltun, G.F.; Nardi, Mark R.; Shaffer, Kimberly H.
Hydrologic and hydraulic analyses for the Black Fork Mohican River Basin in and near Shelby, Ohio
Hydrologic and hydraulic analyses were done for selected reaches of five streams in and near Shelby, Richland County, Ohio. The U.S. Geological Survey (USGS), in cooperation with the Muskingum Watershed Conservancy District, conducted these analyses on the Black Fork Mohican River and four tributaries: Seltzer Park Creek, Seltzer Park Tributary,...
Huitger, Carrie A.; Ostheimer, Chad J.; Koltun, G.F.
Hydrologic effects of potential changes in climate, water use, and land cover in the Upper Scioto River Basin, Ohio
This report presents the results of a study to provide information on the hydrologic effects of potential 21st-century changes in climate, water use, and land cover in the Upper Scioto River Basin, Ohio (from Circleville, Ohio, to the headwaters). A precipitation-runoff model, calibrated on the basis of historical climate and streamflow data, was...
Ebner, Andrew D.; Koltun, G.F.; Ostheimer, Chad J.
An evaluation of the accuracy of modeled and computed streamflow time-series data for the Ohio River at Hannibal Lock and Dam and at a location upstream from Sardis, Ohio
Between July 2013 and June 2014, the U.S. Geological Survey (USGS) made 10 streamflow measurements on the Ohio River about 1.5 miles (mi) downstream from the Hannibal Lock and Dam (near Hannibal, Ohio) and 11 streamflow measurements near the USGS Sardis gage (station number 03114306) located approximately 2.4 mi upstream from Sardis, Ohio. The...
Koltun, G.F.
An analysis of potential water availability from the Charles Mill, Clendening, Piedmont, Pleasant Hill, Senecaville, and Wills Creek Lakes in the Muskingum River Watershed, Ohio
This report presents the results of a study to assess potential water availability from the Charles Mill, Clendening, Piedmont, Pleasant Hill, Senecaville, and Wills Creek Lakes, located within the Muskingum River Watershed, Ohio. The assessment was based on the criterion that water withdrawals should not appreciably affect maintenance of...
Koltun, G.F.
An analysis of potential water availability from the Atwood, Leesville, and Tappan Lakes in the Muskingum River Watershed, Ohio
This report presents the results of a study to assess potential water availability from the Atwood, Leesville, and Tappan Lakes, located within the Muskingum River Watershed, Ohio. The assessment was based on the criterion that water withdrawals should not appreciably affect maintenance of recreation-season pool levels in current use. To...
Koltun, G.F.
Methods for estimating selected low-flow statistics and development of annual flow-duration statistics for Ohio
This report presents the results of a study to develop methods for estimating selected low-flow statistics and for determining annual flow-duration statistics for Ohio streams. Regression techniques were used to develop equations for estimating 10-year recurrence-interval (10-percent annual-nonexceedance probability) low-flow yields, in cubic feet...
Koltun, G.F.; Kula, Stephanie P.
Application of AFINCH as a tool for evaluating the effects of streamflow-gaging-network size and composition on the accuracy and precision of streamflow estimates at ungaged locations in the southeast Lake Michigan hydrologic subregion
Bootstrapping techniques employing random subsampling were used with the AFINCH (Analysis of Flows In Networks of CHannels) model to gain insights into the effects of variation in streamflow-gaging-network size and composition on the accuracy and precision of streamflow estimates at ungaged locations in the 0405 (Southeast Lake Michigan)...
Koltun, G.F.; Holtschlag, David J. Statistical assessment of DNA extraction reagent lot variability in real-time quantitative PCR
Aims: The aim of this study was to evaluate the variability in lots of a DNA extraction kit using real-time PCR assays for Bacillus anthracis, Francisella tularensis and Vibrio cholerae. Methods and Results: Replicate aliquots of three bacteria were processed in duplicate with three different lots of a commercial DNA extraction kit. This...
Bushon, R.N.; Kephart, C.M.; Koltun, G.F.; Francy, D.S.; Schaefer, F. W.; Lindquist, H.D. Alan
GCLAS (Graphical Constituent Loading Analysis System): A tool for computing loads of constituents transported in rivers
GCLAS is a program designed to compute daily and annual loadings of constituents transported in rivers.