The GetWET Observatory was developed as part of an overall course redesign of the Introductory Geology Laboratory at Colorado State University to improve student learning of key surface and groundwater concepts for nonmajors in science, technology, engineering, and mathematics. Consisting of six groundwater monitoring wells, the GetWET Observatory is adjacent to a gauged perennial creek on campus property. Students complete hands-on, field-based exercises related to surface and groundwater, with emphasis on local water quantity and quality. Overarching questions about the responsiveness of the curricular changes to student's needs were evaluated through a student perception survey. The effectiveness of student learning of key concepts of surface and groundwater was evaluated through pre- and post-knowledge assessments. Results of the perception survey indicate that the needs of students from all majors and colleges were equally met, that males report a higher rate of enjoyment of the GetWET experience than females, that weather plays an important role in student enjoyment, that modifications to the groundwater exercise focused the learning on larger concepts of surface and groundwater, and that student perceptions of the quality of the lesson increased with the curricular revision. Student responses indicate we have created an affirmative laboratory environment at the GetWET that supports positive student attitudes conducive to maximum learning. Students whose teaching assistant was a graduate student had much higher perceptions of the quality of the lab, higher satisfaction with the lab, higher perception of the quality of the lesson, and a better understanding of the relationship between themselves and ground and surface water. There was no significant difference in student knowledge baseline on pre-tests over three semesters of data collection. Mean gains in student scores between pre- and post-tests ranged from 0.63 to 0.76, with a 1.60 mean gain for a small number of laboratory sections taught by graduate teaching assistants who had more hydrogeological background. A decrease in student gain scores followed curricular revision along with a simultaneous significant increase in student's perception of the quality of the lesson. Additional data will be collected to determine if the decrease in gain scores is attributed to teaching assistant composition or a less effective laboratory exercise. Pre- and post-knowledge tests are also useful instruments for tracking basic groundwater knowledge of teaching assistants and their teaching effectiveness. Additional and ongoing training of all GEOL121 teaching assistants has strengthened the overall learning experience for undergraduates at the GetWET Observatory.