Exhibit 99.1 Southwest Water Declares Cash Dividends LOS ANGELES--(BUSINESS WIRE)--Aug. 18, 2006--Southwest Water Company (NASDAQ:SWWC) today announced quarterly cash dividends of $0.0524 per share of common stock and $0.65625 per share of Series A preferred stock. The dividends are payable on October 20, 2006, to stockholders of record as of September 30, 2006. Southwest Water Company provides a broad range of services including water production, treatment and distribution; wastewater collection and treatment; utility billing and collection; utility infrastructure construction management; and public works services. The company owns regulated public utilities and also serves cities, utility districts and private companies under contract. More than two million people from coast to coast depend on Southwest Water for high-quality, reliable service. Additional information may be found on the company's Web site: www.swwc.com. CONTACT: Southwest Water Company DeLise Keim, 213-929-1846 www.swwc.com or PondelWilkinson Inc. Cecilia Wilkinson or Robert Jaffe 310-279-5970 or 310-279-5969 www.pondel.com