Dennis Yanchunas has a Bachelor of Arts degree in mathematics and is a veteran, having served as a commissioned officer with the U.S. Navy before moving to Colorado in 1972. He retired in 2015 from a 42-year career in financial services, but he began a concurrent career in water in 1980, at the entry level, working with various ditch companies.

Yanchunas served 15 years on the City of Longmont Water Board (13 years as chairman); 17 years on the Board of the St. Vrain and Left Hand Water Conservancy District (11 as president); and was appointed to the Northern Board in 2010. He served as President of the Municipal Subdistrict for 10 years and was elected the Northern Water Board President in 2023.

Yanchunas and his wife, Pat, have lived in Longmont since 1972.