The reservoir is impounded at its northeastern end by Wilson Dam. The dam is at (38.9666777, -98.4947876) at an elevation of . The Saline River is the reservoir's main inflow of water from the west. It is also the reservoir's main outflow to the east. Smaller tributaries include Elm Creek, which flows from the south into the western part of the reservoir, and Hell Creek, which feeds the reservoir's southeastern arm.