To cite wq in publications use:

Alan D. Jassby and James E. Cloern (2013). wq: Some tools for exploring water quality monitoring data. R package version 0.3-11. http://cran.r-project.org/package=wq

Corresponding BibTeX entry:

  @Manual{jassby2013wq,
    title = {wq: Exploring water quality monitoring data},
    author = {Alan D. Jassby and James E. Cloern},
    year = {2013},
    note = {R package version 0.3-11},
    url = {http://CRAN.R-project.org/package=wq},
  }