CERTIFICATIONS PETER C, NELSON

Exhibit 31.1
CERTIFICATIONS

I, Peter Nelson, President and Chief Executive Officer of California Water
Service Group, certify that:

1. I have reviewed this Form 10-Q of California Water Service Group;

2. Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect
to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material
respects the financial condition, results of operations and cash
flows of the registrant as of, and for, the periods presented in
this quarterly report;

4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Exchange Act Rules 13a-15(e) and internal control over
financial reporting (as defined in Exchange Act rules 13a-15(f) for
the registrant and have:

a. Designed such disclosure controls and procedures, or caused
such disclosure controls and procedures to be designed under
our supervision, to ensure that material information relating
to the registrant, including its consolidated subsidiaries, is
made known to us by others within those entities, particularly
during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or
caused such internal control over financial reporting to be
designed under our supervision, to provide reasonable
assurance regarding the reliability of financial reporting and
the preparation of financial statements for external purposes
in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant's disclosure
controls and procedures and presented in this report our
conclusions about the effectiveness of the disclosure controls
and procedures, as of the end of the period covered by this
report based on such evaluation; and

d. Disclosed in this report any change in the registrant's
internal control over financial reporting that occurred during
the registrant's most recent fiscal quarter (the registrant's
fourth fiscal quarter in the case of an annual report) that
has materially affected, or is reasonably likely to materially
affect, the registrant's internal control over financial
reporting; and;


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5. The registrant's other certifying officer and I have disclosed,
based on our most recent evaluation of internal control over
financial reporting, to the registrant's auditors and the audit
committee of registrant's board of directors (or persons performing
the equivalent functions):

a. All significant deficiencies and material weaknesses in the
design or operation of internal control over financial
reporting which are reasonably likely to adversely affect the
registrant's ability to record, process, summarize and report
financial information; and

b. Any fraud, whether or not material, that involves management
or other employees who have a significant role in the
registrant's internal control over financial reporting.


Date: August 13, 2003 By: /s/ Peter C. Nelson
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PETER C. NELSON
President and Chief Executive Officer
California Water Service Group

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