akqdecay, Many distributional statistics of USGS daily streamflow hydrographs and other powerful utilities

The akqdecay package in the R language provides for computation of distributional statistics of hydrograph recession (decay) based on N-day-over-day changes of daily-mean streamflows for an arbitrary number of U.S. Geological Survey streamgages. Computations are oriented around what are termed AKQ discharge decay analyses. The analyses are focused on the distributional properties of the N-day-over-day changes, and such changes are defined herein as the inverse of the difference in base-10 logarithms of daily-mean streamflow and hence have units of days per log-cycle change. Linear combinations of order statistics (l-moments) are computed to summarize distributional geometry of these changes, and so-called gfactors (geologic factors) are computed as percentiles of the changes. Hydrograph rises or no change periods can also be considered. Considerable flow-duration curve computations can also be made, and many powerful utilities for annual and decadal data computation and manipulation are implemented including daily streamflow separation with aggregation to monthly values. Features for exploring fixed-interval bias corrections on N-day flood volumes from daily values and unit values of streamflow are also provided.