<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-01-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000727273</issuerCik>
        <issuerName>CADIZ INC</issuerName>
        <issuerTradingSymbol>CDZI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001387874</rptOwnerCik>
            <rptOwnerName>Grant Geoffrey T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CADIZ INC.</rptOwnerStreet1>
            <rptOwnerStreet2>550 SOUTH HOPE STREET, SUITE 2850</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2015-01-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>684</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>123106</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Includes 2,419 shares allocated to the Reporting Person under the 2014 Equity Incentive Plan for services rendered by the Reporting Person as a director of the Issuer for the 12 month period ended June 30, 2014, which shares will vest on January 31, 2015.</footnote>
        <footnote id="F2">These shares are held in five separate trusts, each holding 6,100 shares for the benefit of a child of the Reporting Person.  The trustee of these trusts is not a member of the Reporting Person's immediate family.  The Reporting Person disclaims beneficial ownership for the securities held by these trusts.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Geoffrey T. Grant</signatureName>
        <signatureDate>2015-01-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2015-01-01
0
0000727273
CADIZ INC
CDZI
0001387874
Grant Geoffrey T
C/O CADIZ INC.
550 SOUTH HOPE STREET, SUITE 2850
LOS ANGELES
CA
90071
1
0
0
0
Common Stock
2015-01-01
4
A
0
684
0
A
123106
D
Common Stock
30500
I
By Trust
Includes 2,419 shares allocated to the Reporting Person under the 2014 Equity Incentive Plan for services rendered by the Reporting Person as a director of the Issuer for the 12 month period ended June 30, 2014, which shares will vest on January 31, 2015.
These shares are held in five separate trusts, each holding 6,100 shares for the benefit of a child of the Reporting Person.  The trustee of these trusts is not a member of the Reporting Person's immediate family.  The Reporting Person disclaims beneficial ownership for the securities held by these trusts.
Geoffrey T. Grant
2015-01-05