LYNN – The Water and Sewer Commission?s top executive said Lynn could lose a quarter of its water supply from two local rivers if new, restrictive state regulations are not struck down.The Commission has filed a lawsuit in Superior Court asking a judge to decide whether the state Department of Environmental Protection has the authority to impose conditions to withdraw water from the Ipswich River and Saugus River.Commission Executive Director Daniel O?Neill said the DEP conditions could reduce the 8.9 million gallons a day Water and Sewer withdraws from the Saugus River and 5.3 million gallons a day it takes in the winter and spring from the Ipswich River by 3 million gallons a day.?That?s a worse case scenario,” he said.Since 1988, the Lynn Water and Sewer Commission has withdrawn water from the rivers and has been subject to registrations governing the withdrawls.In the fall of 2007, the Commission moved to renew its request to withdraw water and, on Dec. 31, DEP sent notice that included for the first time new performance standards, conditions and requirements for summer water restrictions, which restricts nonessential outdoor water use during the summer.Boston Attorneys Nancy Kaplan, Cheryl A. Blaine and Keegan Werlin, who filed the Commission complaint, are asking a judge to intervene and declare the action constitutes an error of law, declare that the DEP does not have the authority to regulate conditions on the withdrawal of water and force the DEP to accept the original renewal application submitted by the commission.O?Neill said the restrictions are overridden by conditions for withdrawing water detailed in the 1982 legislation creating Water and Sewer.?We?re saying our enabling legislation trumps their restrictions,” he said.When contacted Friday, DEP spokesman Joe Ferson said he did not have details of the suit and planned to research it.