Deep River is a city in Poweshiek County, Iowa, United States. It is also the name of the township which includes the city. The city population …Deep River is a city in Poweshiek County, Iowa, United States. It is also the name of the township which includes the city. The city population was 249 at the time of the 2020 census. Deep River is located at 41°34′49″N 92°22′27″W / 41.58028°N 92.37417°W. According to the United States Census Bureau, the city has a total area of 0.43 square miles, all land.