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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

Current Report Pursuant to Section 13or 15(d) of The Securities Exchange Act of 1934

Date of Report (date of earliest event reported): May 20, 2026

CALIFORNIA WATER SERVICE GROUP

(Exact name of Registrant as Specified in its Charter)

Delaware<br><br>(State or other jurisdiction<br> of incorporation)	1-13883<br><br>(Commission file number)	77-0448994<br><br>(I.R.S. Employer<br> Identification Number)
1720 North First Street<br>San Jose, California<br><br>(Address of principal executive offices)	95112<br><br>(Zip Code)
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(408) 367-8200

(Registrant’s telephone number, including area code)

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
¨	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act<br>(17 CFR 240.14d-2(b))
¨	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act<br>(17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Shares, par value $0.01	CWT	New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined by Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 7.01.	Regulation FD Disclosure

On May 20, 2026, California Water Service Group (Group) issued a press release (a copy of which is attached hereto as Exhibit 99.1 and incorporated herein by reference) announcing the promotion of Tamara S. Johnson to Vice President, California Operations and Gregory D. Shimansky to Vice President, Rates and Regulatory Affairs effective July 1, 2026.

Item 9.01.	Financial Statements and Exhibits.

We hereby file the following exhibit with this report:

Exhibit No.	Description
99.1	Press Release issued May 20, 2026
104	Cover Page Interactive Data File (embedded within the Inline XBRL document)

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	CALIFORNIA WATER SERVICE GROUP
Date: May 20, 2026	By:	/s/ Martin A. Kropelnicki
	Name:	Martin A. Kropelnicki
	Title:	Chairman, President and Chief Executive Officer

Exhibit 99.1

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**DATE:**May 20, 2026

**CONTACT:**Shannon Dean, (408) 367-8243

ForImmediate Release

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CaliforniaWater Service Group Promotes Tamara S. Johnson to

Vice President, California Operations and Gregory D. Shimansky to

Vice President, Ratesand Regulatory Affairs.

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SAN JOSE, Calif., May20, 2026 - At its meeting today, the California Water Service Group (CWT: NYSE) Board of Directors unanimously approved the promotions of Tamara S. Johnson to Vice President, California Operations, and Gregory D. Shimansky to Vice President, Rates and Regulatory Affairs, effective July 1, 2026.

Prior to joining the executive team, Johnson served as Director of Field Operations, Southern California Region. She brings 40 years of public water utility experience to the position, having started her career at California Water Service, Group's largest subsidiary, in 1985. Johnson holds a Master of Business Administration from California State University, Monterey Bay, a Bachelor of Science in Business Administration from the University of La Verne, as well as a Water Treatment Operator License Grade 3 and a Water Distribution License Grade 5 from the State of California. The Vice President, California Operations role is newly created.

"This new position reflects our company's growth and the increasing complexity of water utility operations. Tammy is not only a water utility operations expert, she's also an accomplished professional with a track record of getting things done. It's truly a pleasure to welcome to the officer team someone who has dedicated her entire career to the company," said Chairman and Chief Executive Officer Martin A. Kropelnicki.

Shimansky joined California Water Service Group in 2024 as a director focused on rates and regulatory affairs outside of California. Before joining the Group, he served as Rates and Regulatory Affairs Director at Indiana American Water and General Rate Case Program Manager at San Diego Gas and Electric. He holds a Master of Science in Management from Purdue University and a Bachelor of Arts in Economics from the University of California, Los Angeles. He succeeds Greg A. Milleman, who is retiring after a distinguished 10-year career at Group.

"Greg is results-oriented, and he has done a tremendous job for us thus far. I believe he will be a real asset to the Company as we continue to pursue regulatory mechanisms and rate designs that help keep our rates affordable for customers while allowing us to make the investments in water system infrastructure that help keep our water service safe and reliable," Kropelnicki said.

About CaliforniaWater Service Group

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Group is the parent company of regulated utilities California Water Service, Hawaii Water Service, New Mexico Water Service, and Washington Water Service, as well as Texas Water Service, a utility holding company. Together, these companies provide regulated and non-regulated water and wastewater service to more than 2.1 million people in California, Hawaii, New Mexico, Washington, and Texas. Group’s common stock trades on the New York Stock Exchange under the symbol “CWT.” Additional information is available online at www.calwatergroup.com.