In-depth effort to map the Red River Survey to gather data on bottom elevations from South Dakota to Lake Winnipeg Save to Read Later A complete bathymetric survey of the Red River, which is similar to a topographical map but of river bottom elevations, hasn’t been done in more than 70 years. (Mike Deal / Winnipeg Free Press files) As water sources dry up and climate extremes cause drought and floods on the Prairies, a massive effort is underway to map the bottom of the Red River to measure its depth from South Dakota to Lake Winnipeg. As water sources dry up and climate extremes cause drought and floods on the Prairies, a massive effort is underway to map the bottom of the Red River to measure its depth from South Dakota to Lake Winnipeg.