Status of the common muskrat (Ondatra zibethicus) in the southern High Plains and western Rolling Plains has remained uncertain due to a scarcity of records. I examined diversity of riparian habitats, frequency of occurrence of habitats, availability of habitats, and use of habitats by muskrats within an irrigation drainage system in southwestern Oklahoma during prolonged drought. Six major habitats were supported in 31 km of drainage channels. These included, in order of descending frequency, emergent cattails, prairie sedge meadow, cattail-forested transition, forest, turf grass, and pioneer mudflat. Of habitats in drainage systems, 60% were available for muskrats as defined by presence of water. Availability differed among habitats; prairie sedge meadow had highest availability and emergent cattails was the lowest in availability. Use of habitats differed significantly among habitats and was driven by availability.