Climate change literacy plays a key role in promoting sound political decisions and promoting sustainable consumption patterns. Based on evidence suggesting that student understanding and interest in climate change is best accomplished through studying local effects, we developed a simulation/game exploring the impact of climate change on the declining water levels in Lake Mead. Because there are few evaluations of educational games using true control groups, this study also presents a randomized field trial evaluating the game. We randomly assigned 119 seventh graders to either a game-based condition or control condition. Students in the experimental group played Losing the Lake; those in the control group viewed an earth science website. Students also completed pretest, posttest, and delayed posttest measures of their content understanding and interest in issues embodied in the game. We found that playing the game resulted in a significant increase in content knowledge, as measured by a 22-item assessment, especially on items related to household conservation and some basic concepts related to the greenhouse effect. The control group showed no effect. Playing the game also resulted in some increase in student interest. The Losing the Lake game illustrates how use of a water theme can be used to make climate change content more meaningful and relevant to students. Furthermore, the study shows, through a randomized control trial, that educational games can result in conceptual development, specifically on water flow (i.e., where drinking water comes from and where it goes once used), water conservation, and the difference between weather and climate. The Losing the Lake game can therefore be useful educationally in various locales as a case study in the nature of drought, climate change effects, and water conservation practices.