<SEC-DOCUMENT>0001127602-23-008929.txt : 20230304
<SEC-HEADER>0001127602-23-008929.hdr.sgml : 20230304
<ACCEPTANCE-DATETIME>20230303192222
ACCESSION NUMBER:		0001127602-23-008929
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20230301
FILED AS OF DATE:		20230303
DATE AS OF CHANGE:		20230303

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Milleman Greg A
		CENTRAL INDEX KEY:			0001763798

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13883
		FILM NUMBER:		23706956

	MAIL ADDRESS:	
		STREET 1:		1720 NORTH FIRST STREET
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95112

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CALIFORNIA WATER SERVICE GROUP
		CENTRAL INDEX KEY:			0001035201
		STANDARD INDUSTRIAL CLASSIFICATION:	WATER SUPPLY [4941]
		IRS NUMBER:				770448994
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1720 N FIRST ST
		STREET 2:		C/O CALIFORNIA WATER SERVICE CO
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95112
		BUSINESS PHONE:		4083678200

	MAIL ADDRESS:	
		STREET 1:		1720 FIRST ST
		STREET 2:		C/O CALIFORNIA WATER SERVICE CO
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-03-01</periodOfReport>

    <issuer>
        <issuerCik>0001035201</issuerCik>
        <issuerName>CALIFORNIA WATER SERVICE GROUP</issuerName>
        <issuerTradingSymbol>CWT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001763798</rptOwnerCik>
            <rptOwnerName>Milleman Greg A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1720 N. FIRST STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN JOSE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>VP, Rates and Regulatory Aff</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-03-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>228</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>55.90</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5058</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-03-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>36</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>56.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5022</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents the number of shares withheld by and surrendered to the Issuer to satisfy the tax withholding obligations that arose in connection with the vesting of the Restricted Stock (RSA) Award #643.</footnote>
        <footnote id="F2">Represents the number of shares withheld by and surrendered to the Issuer to satisfy the tax withholding obligations that arose in connection with the vesting of the Restricted Stock (RSA) Award #600.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michelle R. Mortensen on behalf of Greg A Milleman</signatureName>
        <signatureDate>2023-03-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
