A prominent Portland lawyer is presiding over a U.S. Supreme Court case that could have major implications for the states of Florida and Georgia.

Ralph I. Lancaster Jr., an attorney with Pierce Atwood of Portland who lives in Falmouth, was appointed a “special master” by the Supreme Court in the longstanding fight between the states over the supply of water in a shared watershed.

A hearing on the lawsuit, filed by Florida against Georgia, is scheduled to begin Monday in federal court in Portland.

The Associated Press reported that arguments are expected to last for weeks, with the outcome possibly affecting millions of people and major industries in both states.

The dispute centers on the Apalachicola-Chattahoochee-Flint River Basin, a watershed that drains nearly 20,000 square miles in western Georgia, eastern Alabama and the Florida Panhandle.

Florida claims that Atlanta and southwest Georgia farmers are using too much water and hurting Florida’s oyster industry. Georgia argues that limiting its water use will harm the state’s economy, the AP reported.

Florida wants the court to impose a cap on Georgia’s water use, with added restrictions during droughts. Their attorneys will argue that Georgia is responsible for lower river flows across the border to Florida. Georgia wants the court to reject Florida’s request for a water use cap.

Lancaster, who could not be reached for comment Sunday, has been appointed a special master by the Supreme Court on four different occasions, according to a profile posted on his law firm’s website.

Lancaster previously served as trial counsel for the United States in a dispute with Canada that was argued before the International Court of Justice at The Hague. He has been ranked by Chambers USA as one of the best lawyers in America since 1983.

Lancaster tries both civil and criminal cases, locally, nationally and internationally. His case experience ranges from personal injury cases to complex commercial matters, as well as murders, white collar crime and tax evasion. He also handles admiralty matters.

According to court documents filed in case of Florida v. Georgia, Lancaster was appointed special master on Nov. 19, 2014.

The Supreme Court chose Lancaster because the justices don’t have the time to review hours of testimony and reams of evidence, the AP reported.

One discovery filing from September 2015 says that Florida has mobilized a large document review team. To date, the filing goes on to say, Florida has produced approximately 660,000 emails, more than 100,000 pages of electronically stored information and nearly 90,000 documents from third parties.

“In all, Florida has produced more than 3 million pages of documents in response to Georgia’s document requests,” the filing says.

After both sides have presented their evidence and arguments, Lancaster will make a recommendation to the Supreme Court.

Justices will consider his recommendations and hear rebuttals by the states before issuing their final ruling, probably sometime in 2017.