Water use in the United States is uncertain as our climate warms and our population continues to grow. As such, it is imperative that we understand the drivers of water use in order to better plan for this future. The Rio Grande Basin (RGB) in the Southwestern United States presents an opportunity to study these drivers and the spatiotemporal relationships among them as it is a region experiencing rapid population growth in addition to being spatially heterogeneous. In this study, I use statistical analysis in R and ArcGIS Pro to examine the relationship between population, developed land cover, and agricultural land cover on water use in the RGB and how these relationships have changed from 1990 - 2015. The results of this analysis indicate that these relationships are changing both over space and time. While my work here shows a decline in water use in the Rio Grande Basin over the study period, this is attributed to only a handful of counties that experienced a steep decline in agricultural water use. This decrease in agricultural water use likely will not continue to offset the inevitable increase in domestic water use that I begin to see at the end of the study period due to growing populations in the basin. This study reveals that the relationships among population, land use and cover, and water use are dynamic, changing over both time and space, and highlights the need to look deeper into what drives water use in order to address the water needs of a rapidly expanding population.