Edward A. (Ted) Moulder, 56, a retired hydrologist with the U.S. Geological Survey here, died Wednesday at a hospital in St. Petersburg, Fla., where he had been under treatment for an embolism.

He moved to St. Petersburg in 1977 when he retired from the geological survey after more than 30 years of service. For the last four years of his career, he was assistant chief hydrologist for research and technical coordination in the water resources division at the national center in Reston.

He directed research for the survey's national water resources program and the technical aspects of hydrological investigations throughout the 50 states and helped guide aid programs for foreign countries.

Mr. Moulder was born in Lansing, Mich. He served with the Army Air Corps during World War II. He was a student at Michigan State University when he joined the geological survey in 1946. He graduated from the university two years later with a degree in civil engineering.

He directed field investigations of water resources in Montana, Wyoming, Texas and Colorado, and was regional hydrologist of the survey's central region in Denver before coming to the national center in 1973.

Mr. Moulder received the Interio Department's Meritorious Service Award in 1972 and it's Distinguished Service Award in 1978. He was a fellow of the American Society of Civil Engineers and belonged to the American Geophysical Union, the American Institute of Mining Engineers and the American Water Resources Association.

He is survived by his wife, Jimi, of the home in St. Petersburg; a daughter, Jeanne Strickland, and his motherMrs. L. M. Moulder, both of the St. Petersburg area, and three grandchildren.