Digital game-based and gamified technologies hold much promise to promote the development of learners' conceptual knowledge. This efficacy study used desktop virtual reality (dVR) to investigate how the place-based digital gameful learning experience (DGLE) "Watershed Explorers", implemented as a curriculum enhancement activity, impacted students' watershed literacy as well as their attitudes towards playing and learning during dVR gameplay. Thirty-five middle school students completed a pretest-posttest content assessment measuring watershed literacy, a motivation to play with a dVR game survey, and a perception of learning with dVR games survey. Results showed that using "Watershed Explorers" as a curriculum enhancement activity can positively impact learning, especially middle school students' ability to identify their own local watershed and its connections to the ocean. Most participants perceived this DGLE as a helpful and engaging type of learning technology that can promote stimulating ways of presenting content materials and make school learning more interesting. Implications for the design of future iterations of "Watershed Explorers" to enhance learning are also discussed.