Suggested citation for smwrData:

  Lorenz, D.L., 2015, smwrData--An R Package of Example Hydrologic
  Data, Version 1.1.1: U.S. Geological Survey Open-File Report
  2015-1103, 5 p.

A BibTeX entry for LaTeX users is

  @TechReport{,
    title = {smwrData--An R Package of Example Hydrologic Data, Version 1.1.1},
    author = {David L. Lorenz},
    institution = {U.S. Geological Survey},
    series = {Open-File Report},
    year = {2015-1103},
    pages = {5},
    url = {https://pubs.er.usgs.gov/publication/ofr20151103},
  }