Donald A. Williams, 77, the administrator of the Soil Conservation Service in the Department of Agriculture from 1953 until he retired in 1969, died Nov. 12 at Northern Virginia Doctors Hospital. He had mysathenia gravis, a disease of the nervous system.

Mr. Williams began his career with the Soil Conservation Service in 1935 at a Civilian Conservation Corps camp at Presho, S.D. He later worked as a project engineer in the Northwest. He was transferred to Washington in 1950, appointed chief of operations for the SCS in 1951 and administrator in 1953.

Three important programs are associated with Mr. Williams's years as head of the agency. They are the small-watershed program, which seeks to control erosion on tributaries before the runoff reaches major rivers; a conservation program for the Great Plains, and the resource conservation and development program, which provides assistance at local levels.

Mr. Williams once said that he felt his own contribution lay in applying the principles of water conservation to irrigation projects and "integrating water management into the concept of soil and water conservation."

Mr. Williams, who lived in Alexandria, was born in Clark County, S.D., and graduated from South Dakota State College. After retiring from the government, he was a consultant to the governments of Turkey, New Zealand, India and Thailand.

He recieved an honorary doctorate from South Dakota State, the Distinguished Service Award from the Department of Agriculture, the Rockefeller Public Service Award and the first Hugh Hammond Bennett Award from the Soil Conservation Society of America.

He was an elder of the Trinity Presbyterian Church in Arlington.

Survivors include his wife, Ruth, of Alexandria; a daughter, the Rev. Mary Kathryn Weir of London, Ont., Canada; a brother, C.D. Williams of Augusta, S.C., and two grandchildren.