<PAGE>
                                                                   Exhibit 10.50


                                 CAYMAN ISLANDS

                     The Registered Land Law (1995 Revision)
                    The Registered Land Rules (2000 Revision)

                                 Third Schedule

              SECOND COLLATERAL CHARGE TO A VARIATION OF DEBENTURE

                           DATED 22ND OF FEBRUARY 2002

  REGISTRATION SECTION                     BLOCK                       PARCEL
  WEST BAY BEACH NORTH                      11D                           8
----------------------------------         -----                       ------
WE, CONSOLIDATED WATER CO. LTD.
    (hereinafter called " the Chargor")

of P.O. Box 1114 GT, Grand Cayman

HEREBY CHARGE our interest in the above mentioned title to secure the payment

To ROYAL BANK OF CANADA

Of P.O. Box 245 GT, Grand Cayman

Of the principal sum of US$3,000,000.00

With interest at the rate as set our in the attached Schedule,

Payable as set within the attached schedule, subject to Section 67 of the above
Law, save as negatived, modified or added to , in the manner as set out in the
attached Schedule. The Chargee reserves the right to tack and/or consolidate
Charges as set out in the attached Schedule.

         The principle sum shall be repaid on demand together with any interest
or any other monies then due in accordance with attached Schedule.

         And We the above named Chargor hereby acknowledge that We understand
the effect of Section 72 of the Registered Land Law, (1995 Revision).

         Dated this 22nd day of February 2002

                           CONSOLIDATED WATER CO. LTD.

Signed by the Chargor /s/ Frederick Mctaggart       /s/ Peter Ribbins
                     ----------------------------   ----------------------------
                          Director                  Secretary

In the presence of:-
                     -----------------------------------------------------------

Signed by the Chargee            /s/ G. Plamondon
                     -----------------------------------------------------------
                               ROYAL BANK OF CANADA

In the presence of:-            /s/ Denise Ebanks
                     -----------------------------------------------------------

<PAGE>
--------------------------------------------------------------------------------

                              FOR OFFICIAL USE ONLY

    I, the Registrar of Lands in the Cayman Islands hereby certify that this
  document was Received by me for registration on the 6TH day of MARCH 2002 And
    that stamp duty assessed/adjudicated by me/Treasury at CI$ 30.00 and Land
           Registry fees at CI$ 50.00 relating thereto have been paid.

                      REGISTERED this 8TH day of MARCH 2002

                                /s/ illegible
                        ---------------------------------
                             ASST REGISTRAR OF LANDS
                                 CAYMAN ISLANDS

                          CERTIFICATE OF IDENTIFICATION

                           CONSOLIDATED WATER CO. LTD.

                  Name: Frederick W. McTaggart             Director

I HEREBY CERTIFY that the above-named person appeared before me on the...15...
Of ...February, 2002, and being known to me acknowledged the above signature or
mark to be his and that he had freely and voluntarily executed this instrument
and understood its contents.

                               /s/ Jeffrey Parker
               --------------------------------------------------
               Signature and designation of the person certifying


                          CERTIFICATE OF IDENTIFICATION

                           CONSOLIDATED WATER CO. LTD.

                  Name: Peter D. Ribbins                   Secretary

I HEREBY CERTIFY that the above-named person appeared before me on the...15...
Of ......February, 2002, and being known to me acknowledged the above signature
or mark to be his and that he had freely and voluntarily executed this
instrument and understood its contents.

                               /s/ Jeffrey Parker
               --------------------------------------------------
               Signature and designation of the person certifying


<PAGE>



                                 CAYMAN ISLANDS

                     The Registered Land Law (1995 Revision)
                    The Registered Land Rules (2000 Revision)

                                 Third Schedule
              SECOND COLLATERAL CHARGE TO A VARIATION OF DEBENTURE
                           Dated 22nd of February 2002

  REGISTRATION SECTION                     BLOCK                       PARCEL
  WEST BAY BEACH NORTH                      11D                          40
---------------------------                ------                      ------
WE, CONSOLIDATED WATER CO. LTD.
    (hereinafter called " the Chargor")

of P.O. Box 1114 GT, Grand Cayman

HEREBY CHARGE our interest in the above mentioned title to secure the payment

To ROYAL BANK OF CANADA

Of P.O. Box 245 GT, Grand Cayman

Of the principal sum of US$3,000,000.00

With interest at the rate as set our in the attached Schedule,

Payable as set within the attached schedule, subject to Section 67 of the above
Law, save as negatived, modified or added to , in the manner as set out in the
attached Schedule. The Chargee reserves the right to tack and/or consolidate
Charges as set out in the attached Schedule.

         The principle sum shall be repaid on demand together with any interest
or any other monies then due in accordance with attached Schedule.

         And We the above named Chargor hereby acknowledge that We understand
the effect of Section 72 of the Registered Land Law, (1995 Revision).

         Dated this 22nd day of February 2002

                           CONSOLIDATED WATER CO. LTD.

Signed by the Chargor  /s/ Frederick Mctaggart        /s/ Peter Ribbins
                       ----------------------------   --------------------------
                       Director                       Secretary

In the presence of:-
                     -----------------------------------------------------------

Signed by the Chargee                     /s/ G. Plamondon
                      ----------------------------------------------------------
                                        ROYAL BANK OF CANADA

In the presence of:-                      /s/ Denise Ebanks
                     -----------------------------------------------------------

<PAGE>

--------------------------------------------------------------------------------

                              FOR OFFICIAL USE ONLY

    I, the Registrar of Lands in the Cayman Islands hereby certify that this
   document was Received by me for registration on the 6TH day of MARCH 2002
             And that stamp duty assessed/adjudicated by me/Treasury
                at CI$ 30.00 and Land Registry fees at CI$ 50.00
                        relating thereto have been paid.

                      Registered This 8th Day of March 2002

                                  /s/ illegible
                        ---------------------------------
                             ASST REGISTRAR OF LANDS
                                 CAYMAN ISLANDS

                          CERTIFICATE OF IDENTIFICATION

                           CONSOLIDATED WATER CO. LTD.

                Name: Frederick W. McTaggart          Director

I HEREBY CERTIFY that the above-named person appeared before me on the...15...
Of ...February, 2002, and being known to me acknowledged the above signature or
mark to be his and that he had freely and voluntarily executed this instrument
and understood its contents.

                               /s/ Jeffrey Parker
               --------------------------------------------------
               Signature and designation of the person certifying


                          CERTIFICATE OF IDENTIFICATION

                           CONSOLIDATED WATER CO. LTD.

                  Name:  Peter D. Ribbins            Secretary

I HEREBY CERTIFY that the above-named person appeared before me on the...15...
Of ......February, 2002, and being known to me acknowledged the above signature
or mark to be his and that he had freely and voluntarily executed this
instrument and understood its contents.

                               /s/ Jeffrey Parker
               --------------------------------------------------
               Signature and designation of the person certifying




<PAGE>

                  THE REGISTRAR OF LANDS IS HEREBY REQUESTED:-

(a)      to register this Charge in favor of the Chargee,


(b)      to note on the register that the attached Schedule contains an
         agreement by the Chargor with the Chargee that the Chargor will not
         without first obtaining the prior written consent of the Chargee lease
         or sub-lease or agree to lease or sub-lease or accept surrenders of
         leases or sub-leases or transfer or otherwise part with the possession
         of the Charged Premises or any part thereof,

(c)      to note on the register that the right to tack and rank in priority to
         any subsequent charge is expressly reserved to the Chargee,


(d)      to note on the register that the attached Schedule reserves to the
         Chargee the right to consolidate this Charge with any other charge,


(e)      to note on the register that the attached Schedule contains an
         agreement by the Chargor with the Chargee that the Chargor will not
         without first obtaining the prior written consent of the chargee create
         or purport or attempt to create any charge incumbrance or mortgage
         which by virtue of any law or regulation will rank pari passu with or
         in priority to this Charge or second or subsidiary to this Charge.




<PAGE>

                                  THE SCHEDULE

                               Within referred to

It is hereby further agreed and the Chargor and the Chargee hereby respectively
covenant with each other as follows:-

1.(a)    That the Chargor shall repay to the Chargee all Sum and/or interest and
         any other monies payable in accordance with the terms and conditions,
         covenants and agreements contained herein and in the Debenture and
         subsequent Supplemental Debentures and Variation of Debenture and
         Commitment letter,

  (b)    The rate of interest payable hereunder shall be such rate as is
         ascertained by the Chargee (as well after as before any judgment ) to
         be 1 1/2% above US$LIBOR. The interest rate shall be ascertained by the
         Chargee on the date hereof and shall be recalculated periodically I
         line with variations in the general level of interest rates until the
         Principal Sum and interest thereon or on the balance thereof
         outstanding from time to time and all other sums payable hereunder
         shall have been paid to the Chargee PROVIDED THAT if the date for
         calculation of interest hereunder shall fall on a day which is not a
         business day such calculating shall be made on the next succeeding
         business day and for the purposes of this sub-clause the words "
         business day" shall mean a day when banks are open for business in the
         Cayman Islands and New York City, U.S.A.

  (c)    The Chargor shall be at liberty during the continuance of this security
         to make Repayment of any part of the Principal Sum in accordance with
         the terms and conditions as set our in the Commitment Letter dated 25th
         April 2001. Repayment will be accepted by the Chargee provided that any
         such repayment of part must be of at least One Thousand United States
         Dollars or a multiple thereof and provided that any such repayment of
         part must be made on a monthly installment date hereinbefore mentioned
         and upon such additional payment being made principal and interest
         shall continue to be payable at a rate not less than that provided for
         in sub-clause 1 (a) hereof,

  (d)    The Chargor shall be at liberty at any time during the continuance of
         this security make repayment in accordance with the terms and
         conditions as set out in the Commitment Letter dated 25th April 2001.
         Any repayment of the whole of the Remaining balance of the Principal
         Sum and interest and any other monies due at The date of repayment
         shall be made as notified in writing by the Chargee to the Chargor.

2.(a)    If the Chargor shall repay to the Chargee the Principal Sum and
         interest thereon by the installments and at the times and in manner
         hereinbefore provided within seven(7) days after the dates on which the
         same are hereinbefore made payable and if the Chargor shall also
         perform and observe all the covenants conditions and stipulations
         herein contained or implied and on the Charger's part to be performed
         and observed other than the covenants for payment of the said
         installments then the Chargee shall accept such repayments of principal
         and interest by the said installments as aforesaid and the Chargee will
         not take steps to enforce the payment of the Principal Sum and interest
         or any part thereof.





<PAGE>

(b)      Provided always and it is hereby agreed that upon payment to the
         Chargee of the Principal Sum and interest and all other monies payable
         hereunder as notified in writing by the Chargee to the Chargor the
         Chargee will at any time thereafter upon reasonable notice and upon the
         request and at the cost of the Chargor discharge this Charge.

3.       Sub section (c) of Section 67 of the Registered Land Law (1995
         Revision) (hereinafter called "the above Law") (and sub-section (j)
         thereof only so far as it relates to the said sub-section (c)) shall
         not apply to this Charge nor to any instrument of variation executed
         pursuant to this Charge and instead thereof the Chargor shall keep or
         cause to be kept the Charged Premises and all such buildings or
         erections as may become for the time being subject hereto in good and
         substantial repair and condition and permit the Chargee and the agents
         of the Chargee at all reasonable time during the day time and without
         any further consent to enter into and upon the Charged Premises and
         inspect the same and view the state thereof and upon receipt of notice
         in writing from the Chargee shall immediately remedy restore repair
         amend and make good all such effects decays wants of reparation
         amendments and upkeep of the said buildings and erections and the gates
         walls and fences on the Charged Premises as the Chargee may require and
         if the Chargor shall neglect to do so that the Chargee may enter upon
         the Charged Premises with or without workmen or others from time to
         time in order to repair and keep in repair the same and without thereby
         becoming liable as a Chargee in possession and that the expenses of so
         doing shall be repaid by the Chargor to the Chargee on demand and in
         the meantime shall be added to the Principal Sum and bear interest
         accordingly.

4.       Sub-section (d) of Section 67 of the above Law (and sub-section (j)
         thereof only so far as it relates to the said sub-section (d)) shall
         not apply to this Charge nor to any instrument of variation executed
         pursuant to this Charge and instead thereof the Chargor shall so long
         as any money shall remain owing on the security of this Charge or any
         variation thereof insure and keep insured in their full insurable value
         any buildings or erections from time to time erected or in the course
         of erection on the Charged Premises with an insurance office of repute
         approved from time to time by the Chargee and against riot strike
         public liabilities fire lightning flood earthquake volcanic eruption
         hurricane cyclone tornado windstorm and any such other hazards and
         risks as the Chargee may from time to time require AND will punctually
         pay every sum from time to time payable for keeping on foot every such
         insurance or within seven (7) days after the first day upon which it
         becomes payable and will cause a note of this Charge's interest
         hereunder to be endorsed as aforesaid or other proper evidence of the
         subsistence thereof and also on demand deliver to the Chargee the
         receipt for or other sufficient evidence of payment of every sum
         payable as aforesaid AND that if the Chargor shall make default in any
         of the above matters the Chargee may insure and keep insured all or any
         of the said buildings in manner aforesaid and that the expense of so
         doing shall be paid by the Chargor to the Chargee on demand and in the
         meantime shall be added to the Principal Sum hereby secured and bear
         interest accordingly AND it is hereby agreed and declared that all
         monies received under or by virtue of any insurance as aforesaid
         whether received by the Chargor the Chargee or any receiver appointed
         by the Chargee (notwithstanding the provisions of Section 73 (7 ) of
         the above Law ) shall at the option of the Chargee either be forthwith
         applied in or towards substantially rebuilding reinstating or repairing
         the buildings or erections destroyed or damaged or in or towards
         payment of the monies for the time being secured by these presents
         including any premiums paid under the aforesaid power.

5.       The Chargor shall on the date hereof effect an insurance policy in
         respect of damage to the charges premises in a sum at least equal to
         the Principal Sum and interest and any other sums owing or outstanding
         upon the security of this Charge with an insurance company approved by
         the Chargee.




                                       2
<PAGE>

6.       Sub-section (f) and (g) of Section 67 of the above Law shall not apply
         to this Charge nor to any instrument of variation executed pursuant to
         this Charge and instead thereof the Chargor shall not during the
         continuance of this Charge without first obtaining the prior written
         consent of the Chargee lease or sub-lease or agree to lease or
         sub-lease or accept surrenders of leases or sub-leases or transfer or
         otherwise part with the possession of the charges premises or any part
         thereof.

7.       The right contained in Section 82 of the above Law to consolidate this
         Charge with any other charge is expressly reserved to the Chargee and
         the right to tack and rank in priority to any subsequent charge as
         contained in Section 81 of the above Law in respect of further advances
         made to the Chargor is also expressly reserved to the Chargee.

8.       The Chargor shall not create or purport or attempt to create any charge
         incumbrance or mortgage which by virtue of any law or regulation will
         rank pari passu with or in priority to this Charge or second or
         subsidiary to this Charge to act in any way which shall have the effect
         of diminishing or decreasing the valued of the security of this Charge
         without first obtaining the prior written consent of the Chargee.

9.       The Chargor shall not without the prior written consent of the Chargee
         make or permit or suffer to be made any material change to or addition
         whatsoever inn or to the Charged Premises or the use thereof.

10.      The Chargor shall pay all reasonable lawyer's costs and other costs and
         expenses that may be incurred by the Chargee of and incidental to the
         preparation completion stamping and registration of this Charge or any
         variation hereto and the protection and enforcement from time to time
         of the Chargee's rights hereunder.

11.      The Chargor covenants that the Chargor will on demand both before and
         after the security constituted hereby has become enforceable at the
         Chargor's own cost and expense during the continuance of this Charge do
         and execute or cause to be done and executed all such instruments acts
         deeds and things to perfect this security and to preserve and protect
         the rights and privileges of the Chargee granted by this Charge or by
         operation of law and to this end the Chargor hereby undertakes and
         agrees on demand to execute cause to be verified and delivered to the
         Chargee a power of attorney in form required by the Chargee in favour
         of the Chargee to enable the Chargee to register the same in the
         register of powers of attorney at the expense of the Chargor or with
         consent of the Registrar of Lands to file a copy thereof certified by
         the Registrar of Lands in the file of powers of attorney.

12.      In the event that the Chargor shall fail to discharge all monies and
         liabilities in full in accordance with the terms hereof or in the event
         that the Chargor shall be in breach of any of the Chargor's covenants
         or obligations herein contained whether expressed or implied or in the
         event that the Chargor commits any act of bankruptcy or makes any
         assignment or composition for the benefit of the Chargor's creditors or
         being a company goes into liquidation (other than a voluntary
         liquidation for the purposes of a reconstruction only the terms of
         which have been previously approved in writing by the Chargee ) or
         suffers the appointment of a receiver over any part of the Chargor's
         assets then in any such event the whole of the Principal Sum and all
         interest thereon and any other sums owing hereunder to the Chargee
         shall become immediately due and payable and the provisions of Sections
         72 to 75 of the above Law shall apply subject to the modifications
         hereinafter set forth;-



                                       3
<PAGE>

         (i)      the power of sale and of appointing a receiver and any other
                  remedies available to the Chargee shall become immediately
                  exercisable without further notice.

         (ii)     in addition to the remedies provided by Section 72 of the
                  above Law the Chargee shall have the right to foreclose or
                  enter into possession of the charges premises or both in the
                  same circumstances as would allow the Chargee to exercise its
                  power of sale or appoint a receiver.

         (iii)    in the event that the Chargee does appoint a receiver or enter
                  into possession of the Charged Premises the Chargee shall be
                  entitled to exercise its power of sale or Foreclosure at any
                  time thereafter without further notice

         (iv)     upon the exercise of its power of sale the Chargee shall have
                  the right to sell the Charged Premises by private treaty as
                  well as by public auction

         (v)      wherever there is a reference in Section 73 (6) of the above
                  Law to "five percent" this shall be read as "ten percent"

         (vi)     a receiver appointed by the Chargee shall have such powers in
                  addition to those set out in the above Law or any other law
                  relating thereto as the Chargee shall deem necessary
                  (including the right to sell the Charged Premises ) for the
                  proper enforcement and protection of the Chargee's rights
                  hereunder.

PROVIDED ALWAYS and its is herby expressly declared and agreed that in any case
where any such modification of the above Law (or any other modification provided
for in this Charge) shall require the sanction of the Court the Chargee shall
have the right at its option to waive any modification where it is in favor of
the Chargee to do so or to seek the sanction of the Court thereto and should the
Chargee fail to obtain the sanction of the Court to any particular modification
or should the Chargee elect to waive its rights under any modification then the
original provisions of the above Law shall apply without modification.

13.      This Charge is not assignable alienable or transferable by the Chargor.


14.      The Chargee may at any time transfer and assign the benefit of this
         Charge.


15.      No neglect omission or forbearance on the part of the Chargee to take
         advantage of or enforce any right arising out of any breach
         non-observance or non-performance of any covenant or condition herein
         contained or by law implied shall be deemed to operate as a general
         waiver of such covenant or condition or the right to take advantage
         thereof either original or recurring.

16.      The taking of judgment or judgments on any covenants contained in this
         Charge shall not operate as a merger of the said covenant or covenants
         or affect the Chargee's right to interest pursuant to the terms of this
         Charge.




                                       4
<PAGE>

17.      The Chargee shall not be liable for any loss which may occur by reason
         of the exercise or execution of any or all of its remedies and powers
         conferred given or implied by this Charge or by the Laws of the Cayman
         Islands.

18.      In the event that the Chargor is a Company the Chargor hereby
         represents and warrants to the Chargee that it is duly incorporated and
         existing in good standing under the Laws of the Cayman Islands (or
         under the Laws of some other jurisdiction and duly registered to carry
         on business in the Cayman Islands) and that it is qualified to do
         business wherever necessary to carry on its present operations and that
         the making and performance of this Charge is within its corporate
         powers having been properly authorized by all necessary governmental
         and corporate approvals and does not contravene any law or any
         contractual restriction binding on the Chargor and that the Charge is a
         legal valid and binding obligation of the Chargor enforceable against
         the Chargor in accordance with its terms and that there are no pending
         or threatened actions or proceedings before any court or administrative
         agency which may materially adversely affect the Chargor's financial
         conditions and operations.


19.      This Schedule shall be governed and construed solely accordingly to the
         Laws of the Cayman Islands.


20.      Any notice required to be given to or served on the Chargor or Chargee
         under these presents shall be deemed to be sufficiently served on or
         given to the Chargee if service thereof is in compliance with
         provisions of section 153 of the Registered Land Law (1995 Revision) as
         the same may be amended from time to time.

21.(a)   The expression "this Charge" shall mean the Charge annexed hereto
         as negatived modified or added to by this Schedule and all other
         securities provided taken or available to the Chargee thereunder
         including any power of attorney and the expression " the charges
         premises" shall mean the land the subject of this Charge (or any part
         or parts thereof) and all buildings erections fixtures and fittings now
         or from time to time situate thereon or on some part or parts thereof.

   (b)   In this Charge where the context so admits the words importing the
         masculine gender shall include the feminine gender and vice versa and
         words importing the singular number only shall include the plural
         number and vice versa and words importing persons and all reference to
         persons shall include corporations and firms.




                                       5
<PAGE>

(c)      In this Charge where the context so admits the expression "the Chargor"
         shall include persons deriving title under the Chargor or entitled to
         redeem this Charge and the expression " the Chargee" shall include
         persons deriving title under the Chargee to any reference herein to any
         statue or section of any statue shall be deemed to include reference to
         any statutory modification or re-enactment thereof for the time being
         in force.

(d)      If there are two or more parties hereto comprising the Chargor the
         expression "the Chargor" shall throughout mean and include such two or
         more parties and each of them or (as the case may require) such tow or
         more parties or any of them and shall so far as the context so admits
         be construed as well in the plural as in the singular and all covenants
         charges agreements and undertakings herein expressed or implied on the
         part of the Chargor shall be deemed to be joint and several covenants
         charges agreements and undertakings by such parties.




                                       6