- Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Expires: February 28, 2011 Estimated average burden hours per response... 0.5
	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person * Water Asset Management LLC	2. Date of Event Requiring Statement (MM/DD/YYYY) 3/2/2010	3. Issuer Name and Ticker or Trading Symbol SOUTHWEST WATER CO [SWWC]
(Last)        (First)        (Middle) 509 MADISON AVENUE,	4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director                            _____ 10% Owner _____ Officer (give title below)          ___ X ___ Other (specify below) / Member of 10% owner group
(Street) NEW YORK, NY 10022        (City)              (State)              (Zip)	5. If Amendment, Date Original Filed (MM/DD/YYYY)	6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _ X _ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	1173969	I	By TRF Master Fund (Cayman) LP   (1) (2) (3) (4) (5)

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:
( 1)	Water Asset Management LLC, a Delaware limited liability company ("WAM") may be deemed to be a member of a "group", within the meaning of Section 13(d)(3) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), that includes SW Merger Acquisition Corp., a Delaware corporation ("Parent"), TRF Master Fund (Cayman) LP, a Cayman Islands limited partnership (the "WAM Stockholder"), Water Investment Advisors (Cayman) Ltd., a Cayman Islands exempted company (the "WAM General Partner"), Matthew J. Diserio, an individual ("Mr. Diserio"), Disque D. Deane Jr., an individual ("Mr. Deane" and together with WAM, WAM Stockholder, WAM General Partner and Mr. Diserio, the "WAM Investors"), IIF Subway Investment LP, a Delaware limited partnership ("IIF") and IIF Water Manager LLC, a Delaware limited liability company ("IIF GP" together with IIF, the "IIF Investors", and collectively with WAM Investors, the "Investors"). (Continued in footnote 2)
( 2)	WAM Stockholder, WAM General Partner and the IIF Investors are the direct or indirect owners of Parent. WAM is the investment manager of WAM Stockholder. Parent, JPMorgan IIF Acquisitions LLC ("IIF Acquisitions"), WAM and SouthWest Water Company, a Delaware corporation ("SouthWest") have entered into a binding letter of intent, dated March 2, 2010 (the "Binding Letter"), under which Parent is to acquire an aggregate of 2,700,000 shares of common stock of SouthWest (the "Parent Shares"). (Continued in footnote 3)
( 3)	Concurrent with the execution of the Binding Letter, SouthWest, Parent and SW Merger Sub Corp., a Delaware corporation and wholly owned subsidiary of Parent ("Merger Sub") entered into an Agreement and Plan of Merger, dated as of March 2, 2010 (the "Merger Agreement"), pursuant to which Parent will acquire all of the outstanding common stock of SouthWest. Pursuant to the Binding Letter, the acquisition of the Parent Shares is required to take place within 10 business days after the execution of the Merger Agreement. The Binding Letter and the Merger Agreement are separate transactions that include, among other things, different conditions to each party's obligation to close the transaction and different termination rights. (Continued in footnote 4)
( 4)	WAM Stockholder acquired the 1,173,969 shares of common stock of SouthWest reported on this Form 3 (the "WAM Shares") prior to the execution and delivery of the Binding Letter. Each of WAM, WAM General Partner and Messrs. Diserio and Deane expressly disclaims beneficial ownership of any of the shares of common stock of SouthWest that may be beneficially owned by the Investors (other than to the extent of such person's respective pecuniary interests in the WAM Shares) and expressly declares that the filing of this Form 3 shall not be construed as an admission that such person is the beneficial owner of the shares of Common Stock that may be beneficially owned by the Investors (other than to the extent of such person's respective pecuniary interests in the WAM Shares). (Continued in footnote 5)
( 5)	WAM Stockholder expressly disclaims beneficial ownership of any of the shares of Common Stock that may be beneficially owned by the Investors (other than the WAM Shares) and expressly declares that the filing of this Form 3 shall not be construed as an admission that it is the beneficial owner of the shares of Common Stock that may be beneficially owned by the Investors (other than the WAM Shares).

Remarks: The names and addresses of the reporting persons other than WAM (defined below) are set forth on Exhibit I attached hereto.

Reporting Owners
Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Water Asset Management LLC 509 MADISON AVENUE NEW YORK, NY 10022				Member of 10% owner group
TRF Master Fund (Cayman) LP C/O TURNER AND ROULSTONE MANAGEMENT LTD 90 NORTH CHURCH STREET GRAND CAYMAN, E9 KY1-1102				Member of 10% owner group
Water Investment Advisors (Cayman) Ltd. C/O TURNER AND ROULSTONE MANAGEMENT LTD 90 NORTH CHURCH STREET GRAND CAYMAN, E9 KY1-1102				Member of 10% owner group
Diserio Matthew J C/O WATER ASSET MANAGEMENT LLC 509 MADISON AVENUE NEW YORK, NY 10022				Member of 10% owner group
Deane Disque D Jr C/O WATER ASSET MANAGEMENT LLC 509 MADISON AVENUE NEW YORK, NY 10022				Member of 10% owner group

Signatures
/s/ Matthew J. Desario, as President for WATER ASSET MANAGEMENT LLC		3/12/2010
** Signature of Reporting Person		Date
/s/ Matthew J. Desario, as Director for TRF MASTER FUND (CAYMAN) LP		3/12/2010
** Signature of Reporting Person		Date
/s/ Matthew J. Desario, as Director for WATER INVESTMENT ADVISORS (CAYMAN) LTD.		3/12/2010
** Signature of Reporting Person		Date
/s/ Matthew J. Desario		3/12/2010
** Signature of Reporting Person		Date
/s/ Disque D. Deane Jr.		3/12/2010
** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.