Karen R Ryberg, Ph.D.
Research Statistician for the Dakota Water Science Center
Expertise/Projects/Research Interests
- Statistical analysis of hydrologic data, including parametric and nonparametric trend analysis and cluster analysis
- Trend analysis for pesticide concentrations in surface water
- Research related to the impact of climate variability on surface water
- Data mining including automated data retrieval and analysis, outlier detection, and data cleaning
- Machine learning
- Graphical presentation of scientific data
- R - Open Source Statistical Software
- waterData package - Retrieval, analysis, and anomaly calculation of daily hydrologic time series data
- seawaveQ package - A model and utilities for analyzing trends in chemical concentrations in streams with a seasonal wave (seawave) and adjustment for streamflow (Q) and other ancillary variables
- Associate Editor, Hydrological Sciences Journal
- Course Coordinator and member of team teaching Statistical Methods for Environmental Data Analysis at USGS National Training Center
Publications
Ryberg, K.R., 2021, The role of the U.S. Geological Survey in monitoring North Dakota’s environmental conditions: North Dakota Climate Bulletin, v. 15, no. 1, p. 11–14, https://www.ndsu.edu/ndsco/climatesummaries/quarterlyclimatebulletin/.
Helsel, D.R., Hirsch, R.M., Ryberg, K.R., Archfield, S.A., and Gilroy, E.J., 2020, Statistical methods in water resources: U.S. Geological Survey Techniques and Methods, book 4, chapter A3, 458 p., https://doi.org/10.3133/tm4a3. [Supersedes USGS Techniques of Water-Resources Investigat
Education and Certifications
Doctorate of Philosophy, Environmental and Conservation Sciences - Environmental Science Track, 2015 North Dakota State University, Fargo, North Dakota
Dissertation: The impact of climate variability
Master of Science, Statistics, 2006, Colorado State University, Fort Collins, Colorado
Masters Project: Water-quality trend analysis for the Devils Lake Basin, North Dakota, January 1965 through Sept
Associate of Applied Science, Computer Support Specialist, 2003 Bismarck State College, Bismarck, North Dakota
Bachelor of Arts, Mathematics, 1995 Luther College, Decorah, Iowa
Mathematics for Machine Learning Specialization Certificate— Imperial College London on Coursera, 2020
Facilitator Training—Learning to Lead Reflective Conversations, an educational program of Humanities North Dakota and Bismarck State College, Bismarck, ND., 2018
Specialization Certificate in Executive Data Science— Johns Hopkins University on Coursera, 2018
Graduate Certificate, Data Mining and Applications, 2008, Stanford University, Stanford, California
Management, 1996, University of Mary, Bismarck, North Dakota
Science and Products
Flood-frequency estimation for very low annual exceedance probabilities using historical, paleoflood, and regional information with consideration of nonstationarity
seawaveQ—An R package providing a model and utilities for analyzing trends in chemical concentrations in streams with a seasonal wave (seawave) and adjustment for streamflow (Q) and other ancillary variables, version 2.0.0
Landscape drivers of dynamic change in water quality of US rivers
Causal effect of impervious cover on annual flood magnitude for the United States
Causal factors for pesticide trends in streams of the United States: Atrazine and deethylatrazine
Change points in annual peak streamflows: Method comparisons and historical change points in the United States
Modeling drivers of phosphorus loads in Chesapeake Bay tributaries and inferences about long-term change
The U.S. Geological Survey Peak-Flow File Data Verification Project, 2008–16
Structural equation model of total phosphorus loads in the Red River of the North Basin, USA and Canada
Water-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results
2011 Souris River flood—Will it happen again?
Tree-ring-based estimates of long-term seasonal precipitation in the Souris River Region of Saskatchewan, North Dakota and Manitoba
Science and Products
- Publications
Filter Total Items: 49
Flood-frequency estimation for very low annual exceedance probabilities using historical, paleoflood, and regional information with consideration of nonstationarity
Streamflow estimates for floods with an annual exceedance probability of 0.001 or lower are needed to accurately portray risks to critical infrastructure, such as nuclear powerplants and large dams. However, extrapolating flood-frequency curves developed from at-site systematic streamflow records to very low annual exceedance probabilities (less than 0.001) results in large uncertainties in the stAuthorsKaren R. Ryberg, Kelsey A. Kolars, Julie E. Kiang, Meredith L. CarrseawaveQ—An R package providing a model and utilities for analyzing trends in chemical concentrations in streams with a seasonal wave (seawave) and adjustment for streamflow (Q) and other ancillary variables, version 2.0.0
The seawaveQ R package provides functionality and help to fit a parametric regression model, SEAWAVE-Q, to pesticide concentration data from stream-water samples to assess trends. The model incorporates the strong seasonality and high degree of censoring common in pesticide data, and users can incorporate numerous ancillary variables such as streamflow anomalies. The model is fitted to pesticide dAuthorsKaren R. Ryberg, Benjamin C. YorkLandscape drivers of dynamic change in water quality of US rivers
Water security is a top concern for social well-being and dramatic changes in the availability of freshwater have occurred as a result of human uses and landscape management. Elevated nutrient loading and perturbations to major ion composition have resulted from human activities and have degraded freshwater resources. This study addresses the emerging nature of stream water quality in the 21st ceAuthorsEdward G. Stets, Lori A. Sprague, Gretchen P. Oelsner, Henry M. Johnson, Jennifer C. Murphy, Karen R. Ryberg, Aldo V. Vecchia, Robert E. Zuellig, James A. Falcone, Melissa L. RiskinCausal effect of impervious cover on annual flood magnitude for the United States
Despite consensus that impervious surfaces increase flooding, the magnitude of the increase remains uncertain. This uncertainty largely stems from the challenge of isolating the effect of changes in impervious cover separate from other factors that also affect flooding. To control for these factors, prior study designs rely on either temporal or spatial variation in impervious cover. We leverage bAuthorsAnnalise G. Blum, Paul J. Ferraro, Stacey A. Archfield, Karen R. RybergCausal factors for pesticide trends in streams of the United States: Atrazine and deethylatrazine
Pesticides are important for agriculture in the United States, and atrazine is one of the most widely used and widely detected pesticides in surface water. A better understanding of the mechanisms by which atrazine and its degradation product, deethylatrazine, increase and decrease in surface waters can help inform future decisions for water-quality improvement. This study considers causal factorsAuthorsKaren R. Ryberg, Wesley W. Stone, Nancy T. BakerChange points in annual peak streamflows: Method comparisons and historical change points in the United States
Change-point, or step-trend, detection is an active area of research in statistics and an area of great interest in hydrology because change points may be evidence of natural or anthropogenic changes in climatic, hydrologic, or landscape processes. A common change-point technique is the Pettitt test; however, many change-point methods are now available and testing of methods has been limited. ThisAuthorsKaren R. Ryberg, Glenn A. Hodgkins, Robert W. DudleyModeling drivers of phosphorus loads in Chesapeake Bay tributaries and inferences about long-term change
Causal attribution of changes in water quality often consists of correlation, qualitative reasoning, listing references to the work of others, or speculation. To better support statements of attribution for water-quality trends, structural equation modeling was used to model the causal factors of total phosphorus loads in the Chesapeake Bay watershed. By transforming, scaling, and standardizing vaAuthorsKaren R. Ryberg, Joel D. Blomquist, Lori A. Sprague, Andrew J. Sekellick, Jennifer L. KeismanThe U.S. Geological Survey Peak-Flow File Data Verification Project, 2008–16
Annual peak streamflow (peak flow) at a streamgage is defined as the maximum instantaneous flow in a water year. A water year begins on October 1 and continues through September 30 of the following year; for example, water year 2015 extends from October 1, 2014, through September 30, 2015. The accuracy, characterization, and completeness of the peak streamflow data are critical in determining flooAuthorsKaren R. Ryberg, Burl B. Goree, Tara Williams-Sether, Robert R. Mason,Structural equation model of total phosphorus loads in the Red River of the North Basin, USA and Canada
Attribution of the causes of trends in nutrient loading is often limited to correlation, qualitative reasoning, or references to the work of others. This paper represents efforts to improve causal attribution of water-quality changes. The Red River of the North basin provides a regional test case because of international interest in the reduction of total phosphorus loads and the availability of lAuthorsKaren R. RybergWater-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results
Since passage of the Clean Water Act in 1972, Federal, State, and local governments have invested billions of dollars to reduce pollution entering rivers and streams. To understand the return on these investments and to effectively manage and protect the Nation’s water resources in the future, we need to know how and why water quality has been changing over time. As part of the National Water-QualAuthorsGretchen P. Oelsner, Lori A. Sprague, Jennifer C. Murphy, Robert E. Zuellig, Henry M. Johnson, Karen R. Ryberg, James A. Falcone, Edward G. Stets, Aldo V. Vecchia, Melissa L. Riskin, Laura A. De Cicco, Taylor J. Mills, William H. Farmer2011 Souris River flood—Will it happen again?
The Souris River Basin is a 61,000 square kilometer basin in the provinces of Saskatchewan and Manitoba and the state of North Dakota. Record setting rains in May and June of 2011 led to record flooding with peak annual streamflow values (762 cubic meters per second [m3/s]) more than twice that of any previously recorded peak streamflow and more than five times the estimated 100 year postregulatioAuthorsRochelle A. Nustad, Kelsey A. Kolars, Aldo V. Vecchia, Karen R. RybergTree-ring-based estimates of long-term seasonal precipitation in the Souris River Region of Saskatchewan, North Dakota and Manitoba
Historically unprecedented flooding occurred in the Souris River Basin of Saskatchewan, North Dakota and Manitoba in 2011, during a longer term period of wet conditions in the basin. In order to develop a model of future flows, there is a need to evaluate effects of past multidecadal climate variability and/or possible climate change on precipitation. In this study, tree-ring chronologies and histAuthorsKaren R. Ryberg, Aldo V. Vecchia, F. Adnan Akyüz, Wei Lin - Science
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