Donald W. Pritchard, a noted oceanographer whose pioneering studies of the Chesapeake Bay were the foundation for the physics of estuaries, died of a stroke Friday at University of Maryland Medical Center. The Severna Park resident was 76.
Dr. Pritchard, who studied the Chesapeake Bay for 50 years, is most noted for his discovery that the bay contains two layers of water -- lighter, fresh water on top flowing seaward, and heavier, salty water moving up along the bay's bottom.
"Anyone who studies estuaries, be it physics or from the chemistry or ecology of estuaries, has to learn something about Pritchard's circulation of estuaries," said Donald F. Boesch, president of the University of Maryland Center for Science and a trustee of the Chesapeake Bay Foundation.
Dr. Pritchard was born in Santa Ana, Calif., where he met and married Thelma Lydia Amling in 1943.
During World War II, he was a first lieutenant in the Army Air Forces and forecast weather and sea conditions for the Normandy invasion.
After the war, he earned master's and doctoral degrees in oceanography at the Scripps Institution of Oceanography at the University of California. His bachelor's degree was in meteorology from the University of California at Los Angeles.
In 1949, Dr. Pritchard became the first head of the Johns Hopkins University's Chesapeake Bay Institute. A year later, he founded and became the first chairman of Hopkins' oceanography department.
The chance to study the Chesapeake Bay long before it became fashionable gave him "a rather romantic opportunity to solve some of the speculations and mysteries posed more than 340 years previously by that tireless explorer, Capt. John Smith," he wrote in an article in The Sun in 1953.
He wrote that his research helped watermen understand why crabs died when the wind blew their crab pots down to water levels denied oxygen.
In his early years, Dr. Pritchard used crude instruments made of plywood to calculate the speed of the water current, said his protege and former graduate student, Dr. Jerry Schubel, president of the New England Aquarium in Boston.
In addition to his contribution to the scientific study of the bay, he knew how to put "humans into the equation and minimize their impact" on the environment, Dr. Schubel said.
Dr. Pritchard helped design a Baltimore treatment plant that discharged waste water at a depth that would have a minimal effect on the bay. He also designed a system at the Calvert Cliffs nuclear power plant to discharge the heat so it would not harm the bay, Dr. Schubel said.
"He was there at every step of the way. He was a field scientist, an experimentalist, an inventor and a theoretician. He was also the man who applied what it meant to human beings and society," Dr. Schubel said.
He described Dr. Pritchard as having a "restless mind. He was not the kind of person who could ever retire. When he started to play golf, he had to master the physics of golf. When he took up sailing, he had to understand the physics of sailing."
After leaving Hopkins in 1979, Dr. Pritchard worked in various positions in marine sciences at the State University of New York, Stony Brook, until 1988.
At the time of his death, he was an adjunct professor at the University of Maryland.
"He and I had started writing another paper on the bay, comparing the Long Island Sound and the Chesapeake Bay, called 'A Tale of Two Estuaries,' " said Dr. Schubel.
At his home in Severna Park, Dr. Pritchard was a problem-solver for his five children.
When a daughter, Suzanne Lebowitz, became ill with amyotrophic lateral sclerosis, or Lou Gehrig's disease, and was no longer able to speak, he refined a machine that allowed her to communicate "through moving her cheeks lightly and depressing on a pad so she could spell words," said another daughter, Marian Cardwell of Severna Park.
Ms. Lebowitz died in 1994.
Dr. Pritchard was the first winner of the Mathias Medal, named for Maryland's former Republican U.S. Sen. Charles McC. Mathias and awarded for scientific contributions to the Chesapeake Bay. He was the recipient of several other environmental awards.
He was a member of the National Academy of Engineering and a fellow at the International Oceanographic Foundation and the American Geophysical Union.
Services for Dr. Pritchard will be held at 10 a.m. tomorrow at Our Shepherd Lutheran Church, 400 Benfield Road, Severna Park.
In addition to his wife and daughter, he is survived by another daughter, Jo Anne Mitchell of Severna Park; two sons, Donald W. Pritchard Jr. of Severna Park and Albert Pritchard of Harwood; a sister, Virginia Comstock of Santa Ana; 11 grandchildren; and three great-grandchildren.
Sun staff researcher Paul McCardell contributed to this article.
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