<PAGE>   1
                                                                   Exhibit 10.15

                       AMENDMENT OF ENGAGEMENT AGREEMENT

THIS AGREEMENT is made this 26th day of October , 1999.

BETWEEN:       CONSOLIDATED WATER LTD., a Cayman Islands company having its
               registered office at Trafalgar Place, West Bay Road, P.O. Box 11
               14GT, Grand Cayman, B.W.I. (the "Company")


AND:           JEFFREY M. PARKER of 81 Drake Quay,
               Governor's Harbour, P.O. Box 1782, Grand
               Cayman, B.W.I. (the "Chairman")


WHEREAS:




A.   The Company and the Chairman entered into an engagement agreement dated the
     30th of December 1998 (the "Engagement Agreement").

B.   The parties are desirous of amending the same in accordance with the terms
     of this Agreement.

NOW IN CONSIDERATION of the mutual covenants contained herein the parties agree
that the Engagement Agreement shall be amended and/or rectified as follows:

1.       Clause 8 shall be amended by deleting the same and substituting the
         following:

                  "FURTHER, SUBJECT TO ANY APPROVALS OF GOVERNMENT WHICH MAY BE
                  NECESSARY AT THE TIME AT WHICH THE OPTION IS EXERCISED, FOR
                  EACH OF THE THREE FINANCIAL YEARS ENDING DECEMBER 31, 1999,
                  DECEMBER 31, 2000 AND DECEMBER 31, 2001 RESPECTIVELY, PROVIDED
                  (SUBJECT TO PARAGRAPH 21 OF THIS AGREEMENT) THAT THE CHAIRMAN
                  SERVES IN THE CAPACITIES FOR THE ENTIRETY OF SUCH YEAR, ON
                  DECEMBER 31 OF SUCH YEAR, THE CHAIRMAN SHALL BE GRANTED AN
                  OPTION TO PURCHASE, AT A PRICE PER SHARE of US$6.00, PAYABLE
                  IN CASH IN FULL ON THE EXERCISE OF THE OPTION, A NUMBER OF
                  ORDINARY SHARES EQUAL TO THE NUMBER OF US$ WHICH REPRESENTS
                  1% OF THE NET PROFIT OF THE COMPANY CALCULATED AS AFORESAID
                  FOR THAT FINANCIAL YEAR. "

2.       By amending CLAUSE 9 by re-labelling the existing clause 9(a) and
         adding the following sentence:

                  "PROVIDED THAT THE OPTIONS GRANTED PURSUANT TO CLAUSE 8 MAY
                  NOT BE EXERCISED IF OR TO THE EXTENT THAT, IMMEDIATELY
                  FOLLOWING THE EXERCISE, THE CHAIRMAN WOULD BENEFICIALLY OWN
                  MORE THAN 6% OF ALL ORDINARY SHARES THEN ISSUED BY THE
                  COMPANY. "

3.       By adding the following as clause 9(b):

                  "THE OPTIONS GRANTED PURSUANT TO CLAUSE 8 MAY NOT BE ASSIGNED,
                  TRANSFERRED OR OTHERWISE DISPOSED OF BY THE CHAIRMAN WITHOUT
                  THE PRIOR WRITTEN CONSENT OF the COMPANY."


<PAGE>   2




4.       The parties have acknowledged that the Engagement Agreement shall
         remain binding and effective in accordance with its terms except as
         expressly amended hereby.

THE PARTIES HERETO have hereunto set their hands and seals the day and date
first above written.

SIGNED AND SEALED in the presence of: )        CONSOLIDATED WATER
                                      )        LTD.
                                      )
                                      )        /s/ Wilmer Pergande
                                      )        ---------------------------------
                                      )
/s/ Peter D. Ribbins                  )        /s/ Aledander Stephen Bodden
--------------------------------------)        ---------------------------------
witness                               )

SIGNED AND SEALED in the presence of: )
                                      )
                                      )
                                      )
                                      )
/s/ C.B. Flowers                      )        /s/ Jeffrey M. Parker
--------------------------------------)        ---------------------------------
witness                                        Jeffrey M. Parker