To cite wq in publications use:

Alan D. Jassby and James E. Cloern (2015). wq: Some tools for exploring water quality monitoring data. R package version 0.4.3. http://cran.r-project.org/package=wq

Corresponding BibTeX entry:

  @Manual{jassby2015wq,
    title = {wq: Exploring water quality monitoring data},
    author = {Alan D. Jassby and James E. Cloern},
    year = {2015},
    note = {R package version 0.4.3},
    url = {http://CRAN.R-project.org/package=wq},
  }