To cite package 'FlowRegEnvCost' in publications use:

  García de Jalón S, González del Tánago M, Alonso C, García de Jalón D
  (2017). The environmental costs of water flow regulation: an
  innovative approach based on the 'polluter pays' principle. Water
  Resources Management, 31(9), 2809-2822.
  doi:10.1007/s11269-017-1663-0.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {The Environmental Costs of Water Flow Regulation: an Innovative Approach Based on the 'Polluter Pays' Principle},
    author = {Silvestre {García de Jalón} and Marta {González del Tánago} and Carlos Alonso and Diego {García de Jalón}},
    journal = {Water Resources Management},
    year = {2017},
    month = {jul},
    volume = {31},
    number = {9},
    pages = {2809--2822},
    issn = {1573-1650},
    doi = {10.1007/s11269-017-1663-0},
  }