AMENDMENT 2011-1 TO THE PENSION PLAN FOR EMPLOYEES OF AMERICAN WATER WORKS COMPANY, INC. AND ITS DESIGNATED SUBSIDIARIES

Exhibit 10.1

AMENDMENT 2011-1

TO THE

PENSION PLAN FOR EMPLOYEES OF

AMERICAN WATER WORKS COMPANY, INC.

AND ITS DESIGNATED SUBSIDIARIES

Pursuant to the authority reserved to the Board of Directors of American Water Works Company, Inc. (the “Board”) under Paragraph 56 of the Pension Plan for Employees of American Water Works Company, Inc. and its Designated Subsidiaries (the “Plan”) and as permitted under Paragraph 58 of the Plan, the Board hereby amends the Plan, effective as of June 30, 2011, as follows:

“Effective as of July 1, 2011, in connection with that certain Stock Purchase Agreement, dated as of January 23, 2011, by and among the Company, Arizona-American Water Company, New Mexico-American Water Company, Inc. and EPCOR Water (USA), Inc., pursuant to which the Company agreed to sell all of the issued and outstanding stock of Arizona-American Water Company and New Mexico-American Water Company, Inc. to EPCOR Water (USA), Inc., (the “Sale”) the Company is transferring the assets and liabilities attributable to those Participants who are, or were previously, employed by Arizona-American Water Company and New Mexico-American Water Company, Inc. to the Pension Plan for Employees of Arizona-American Water Company and New Mexico-American Water Company, Inc. (the “Arizona-New Mexico Pension Plan”), a new pension plan established for such Participants. Such assets and liabilities include those attributable to active Participants as of June 30, 2011, terminated vested Participants, and retired Participants (or their Beneficiaries) who are receiving benefit payments from the Plan, all of whom are, or were previously, employed by Arizona-American Water Company or New Mexico-American Water Company, Inc. (collectively, the “Arizona-New Mexico Employees”). Any benefit to which an Arizona-New Mexico Employee may have been entitled under the Plan immediately prior to July 1, 2011 shall not be provided under the Plan, but instead shall be provided under the Arizona-New Mexico Pension Plan. In addition, with respect to any Participant who is transferred to the employment of Arizona-American Water Company and New Mexico-American Water Company, Inc. from the Employer on or after July 1, 2011 and prior to the consummation date of the Sale, assets and liabilities with respect to such Participant’s Accrued Benefit under the Plan, if any, shall be transferred to the Arizona-New Mexico Pension Plan. Furthermore, with respect to any participant under the Arizona-New Mexico Pension Plan who transfers employment from Arizona-American Water Company and New Mexico-American Water Company, Inc. to the Employer prior to the consummation date of the Sale, assets and liabilities with respect to such participant’s Accrued Benefit under the Arizona-New Mexico Pension Plan shall be transferred back to this Plan and be payable from this Plan to such transferred participant.

The Arizona-New Mexico Employees described in this paragraph are identified in Appendix 6 attached hereto.”

“EXHIBIT A-1”

LIST OF DESIGNATED SUBSIDIARIES

2

“APPENDIX 6”

Arizona-New Mexico Employees

Effective July 1, 2011, the following Participants shall not be eligible to receive any benefit or future benefit under the Plan –

AWW PARTICIPANTS ON WHOSE BEHALF BENEFITS WERE TRANSFERRED TO THIS PLAN

3

4

5

6

IN WITNESS WHEREOF, and as evidence of the adoption of this Amendment 2011-1 to the Plan set forth herein, the Board has caused this instrument to be executed this 17th day of June, 2011.

7