Robert M Hirsch is a Research Hydrologist Emeritus for the USGS Water Resources Mission Area.
EGRET Software
Exploration and Graphics for RivEr Trends (EGRET) is an R package for evaluating long-term changes in river conditions (water quality and discharge). The EGRET user guide provides guidance on installation and use of the software, documentation of the analysis methods used, as well as information about the kinds of questions and approaches that the software can facilitate.
Statistical Methods in Water Resources
An applied statistics textbook for hydrology, environmental science, environmental engineering, geology, or biology that addresses distinctive features of environmental data. The text utilizes R, a programming language and open-source software environment, for all exercises and most graphics, and the R code used to generate figures and examples is provided for download.
My main interest is improving the analysis of hydrologic data, with a focus on the topic of trends in streamflow and trends in surface water quality. My research on this has resulted in the development of the EGRET software (Exploration and Graphics for RivEr Trends) written in R and available freely online.
The focus of my research is the description and understanding of long-term variability and change in surface-water quality and streamflow. I develop and apply new statistical tools to help characterize these changes to gain the best possible understanding of the nature of the change and its implications from a policy perspective (related to water quality improvement, flood hazard mitigation, water supply planning). This work has resulted in the development of the statistical method Weighted Regressions on Time, Discharge, and Season (WRTDS), which I have applied to the study of water quality trends in a variety of watersheds including Chesapeake Bay, the Mississippi River, Lake Erie, and Lake Champlain. This technique is a central feature of the EGRET R package. That package is designed to be a “toolbox” for analysis of daily streamflow data and surface water quality data.
My other major recent contribution is the publication of "Statistical Methods in Water Resources" the 2020 edition published as USGS Techniques and Methods (tm4A3). In addition to the pdf and the printed book, the text has on-line resources which include all of the data sets used as examples in the book, all of the R code used in the analysis of those data, and all of the R code used to produce the graphics in the book.
I hold a B.A. in Geology from Earlham College, an M.S. in Geology from the University of Washington, and a Ph.D. in Geography and Environmental Engineering at the Johns Hopkins University. I began my USGS career in 1976 and conducted research on water supply, water quality, pollutant transport, and flood frequency analysis. In 1993-1994 I was Acting Director of the USGS, and from 1994-2008 I was the Chief Hydrologist of the USGS. In 2008 I returned to research and since that time I have focused efforts on describing long-term changes in streamflow and water quality. I retired from the USGS in 2018 but continue to collaborate with colleagues inside and outside the USGS. I am a member of the Water Science and Technology Board of the NASEM and have served on four expert committees of that Board.
Science and Products
Evaluating chloride trends due to road-salt use and its impacts on water quality and aquatic organisms
Transport of dissolved organic matter by river networks from mountains to the sea: a re-examination of the role of flow across temporal and spatial scales
Flux of Nitrogen, Phosphorous, and Suspended Sediment from the Susquehanna River Basin to the Chesapeake Bay During Tropical Storm Lee, September 2011, as in Indicator of the Effects of Reservoir Sedimentation on Water Quality
Science and Products
- Science
Evaluating chloride trends due to road-salt use and its impacts on water quality and aquatic organisms
Chloride, a key component of road salt, is soluble, highly mobile in water, and, at high concentrations, can be toxic to aquatic vegetation and wildlife. USGS scientists have been analyzing temporal, seasonal, and environmental trends in chloride concentrations across the U.S. to determine the effects that road salt may be having on water quality and aquatic organisms.Transport of dissolved organic matter by river networks from mountains to the sea: a re-examination of the role of flow across temporal and spatial scales
The transport of dissolved organic matter (DOM) by rivers is an important component of the global carbon cycle, affects ecosystems and water quality, and reflects biogeochemical and hydrological processes in watersheds. Understanding the fundamental relationships between discharge and DOM concentration and composition reveals important information about watershed flow paths, soil flushing, connectFlux of Nitrogen, Phosphorous, and Suspended Sediment from the Susquehanna River Basin to the Chesapeake Bay During Tropical Storm Lee, September 2011, as in Indicator of the Effects of Reservoir Sedimentation on Water Quality
Concentrations of nitrogen, phosphorus, and suspended sediment are measured at the U.S. Geological Survey streamgage at Conowingo Dam at the downstream end of the Susquehanna River Basin in Maryland, where the river flows into the Chesapeake Bay. During the period September 7–15, 2011, in the aftermath of Tropical Storm Lee, concentrations of these three constituents were among the highest ever... - Data
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- Software