EflowStats: An R package to compute ecologically-relevant streamflow statistics

Critical aspects to understanding the ecological health of a river are quantifying the amount of streamflow needed to sustain ecological function and determining how changes in the landscape and climate alter streamflow processes. The natural flow regime concept defines five components of streamflow derived from the daily streamflow time series that have been found to be strongly linked to the ecological health of river systems: 1) magnitude, 2) frequency, 3) duration, 4) timing, and 5) rate of change of streamflow. Streamflow statistics representing these 5 properties have been broadly applied in the literature and the number of ecologically-relevant streamflow statistics (ERSS) available from various software packages is now in the hundreds. Although useful to compute subsets of the ERSS, some of these software packages have limitations, which could include the inability to compute ERSS for many rivers at once, difficulty integrating with other ecological analysis packages, and proprietary licensing. To address these limitations, the U.S. Geological Survey (USGS) National Water Census, in collaboration with the Center for Integrated Data Analytics, has developed EflowStats. The EflowStats package includes the ability to compute a comprehensive set of ERSS using the open source R software environment and provides batch capabilities that allow a user to develop ERSS for multiple sites simultaneously. The EflowStats package will be publicly available and directly integrated into the USGS National Water Census Data Platform. EflowStats will enable easy, transparent, and repeatable calculation of many of the most utilized ERSS for the large number of scientists working in R. In addition, the open-source nature of the R environment will allow for modification or further development of the EflowStats source code.